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NutmegCT
August 5th, 2009, 12:13 PM
Hi folks.

In a different topic here several people gave me some good suggestions on troubleshooting my 1981 Osborne I. The power supply unit, and possibly some main logic board bits, had gone bad.

After a week of searching, I found a working (yes - I saw it work!) Osborne I. Watched it boot up into cp/m on A, then load SuperCalc on B.

So I paid my shekels and drove the six hours to bring it home today. Set it up, power on, saw the opening Osborne screen perfectly, with the Insert System Disk in Drive A text.

Inserted the System disk, hit Return, and watched the *top two lines* of the "Loading cp/m and Help" screen load. At that point the drive stops reading, and the screen slowly starts a random display of a vertical block (a graphic?) character.

Several power cycles, reboots, etc., all result in the same thing. It never gets to the A: prompt.

Tried a copy of the System disk, and the same thing happens, altho' the random graphic is different. As I can't get to the A prompt, I can't check the B drive.

Any suggestions - before I throw myself (and the new OCC) in the path of a moving train?

Thanks.
Tom
PS - interestingly, when the "new" OCC wasn't successful, I pulled the PSU from it and put it in my original OCC. That didn't change a thing. Weird.

dave_m
August 5th, 2009, 01:08 PM
Tom, I am not familiar with the Osborne, but since it experienced a six hour drive, did you reseat all connectors, modules and socketed parts?

If that doesn't help, consider swapping the drives. It seems like it is almost working so hang in there.
-Dave

NutmegCT
August 5th, 2009, 02:36 PM
Tom, I am not familiar with the Osborne, but since it experienced a six hour drive, did you reseat all connectors, modules and socketed parts?

If that doesn't help, consider swapping the drives. It seems like it is almost working so hang in there.
-Dave

Dave - thanks for the positive vibes.

Would you believe it, I actually got it to run perfectly - ONCE! Booted from original Osborne cp/m disk in drive A, loaded perfectly, and I could even do a DIR of drive B.

With a big smile on my face, I ran some cp/m utilities on the B disk, and - unfortunately - decided to try the boot process again.

Back to square one. Saw the opening Osborne screen, started loading the system files from A, screen changed to "Loading Osborne CP/M and Help" on the top two lines, then drive stopped, drive light went off, and a few random graphic characters started slowly appearing across the screen.

Powered off, unplugged, reseated every single removable chip and plug in the entire system, even swapped the two disk drives. No change.

This is strange!

Thanks.
Tom

barythrin
August 5th, 2009, 02:46 PM
I'm not sure what'd be causing the bad characters to slowly go on the screen. I wonder if the floppy drive just needs to be cleaned. Gibberish on the screen is often bad RAM or video ram though (on most common computers, not necessarily an Osborne).

Could also be an overheating problem which they were prone to do which might explain why it works first time but warms up and doesn't. You may be able to get further performance by having a fan blow on the system just to check.

tezza
August 5th, 2009, 03:23 PM
Hmm, yes I love my Ozzy but they can be temperamental. I've had three issues with mine...


Capacitor blowout in power supply (alarming bangs, smoke)
Bad RAM (garbage characters and non boot)
Buzzing disk drive causing power fluctuations (and hence a crash)

You can read about all those three things from the links futher down on this page (http://www.classic-computers.org.nz/collection/osborne.htm).

However, your issue doesn't sound like any of those problems. Osbornes can get RAM issues as I found with mine but (like most ICs) RAM is usually damaged or it's not. I'm wondering if it's a dry solder joint on the circuit board somewhere or maybe, just maybe a faulty capacitor? I had an Apple clone that had a problem where it worked for about 15 seconds, then totally lost the plot. I tracked the problem down to a small bluecap capacitor which failed once it warmed up. Your Osborne starts to boot then fails, so I'm wondering if it's a similar thing?

These kind of problems are not easy to diagnose and the only way I discovered mine was to go back to first principles and trace the fault from the CPU. I was lucky in that, given where the faulty component was, I could isolate the circutry involved quite quickly. That would not be a case with a lot of things though.

If interested, you can read about this Apple clone/capacitor adventure here (http://www.classic-computers.org.nz/blog/2009-03-29-re-repairing-an-apple-II-plus-clone.htm).

Good luck. Having two Osborne 1s I'm sure you can get at least one working machine out of the both of them.

Tez

NutmegCT
August 5th, 2009, 03:43 PM
Hi Tez - there's a goodly number of ram chips and capacitors on the board. How did you find the faulty one? As they're soldered in, I'd imagine they're not all that easy (!) to trace and replace.

Tom

NutmegCT
August 5th, 2009, 05:00 PM
An interesting tid-bit. I tried booting from the B drive (the SHIFT+") combination. No change.

So on the off chance the drives were failing, I swapped with the drives in my first machine (the one with the dead PSU).

Now after getting the power-on Osborne "insert system and press Return", regardless of which drive I boot from, I get "BOOT ERROR" scrolling down the screen when the drive tries to read the system disk.

I *guess* this is progress, as my original Osborne (with the failed PSU) wouldn't even get to the initial Osborne screen.

Both machines are single-side single-density.

Any thoughts?
Thanks.
Tom

NutmegCT
August 5th, 2009, 06:14 PM
PROGRESS!

I went back to the original drives, and no longer get the BOOT ERROR message. Don't have a clue why, but now I get the "Loading CP/M and Help" message again when I boot from the system disk.

As usual, the second screen has "cp/m and help" at the top, and "freezes".

BUT I discovered that regardless of what key I hit when that screen is "frozen", I get a rapid display of the Osborne "Help" screen. Hitting any key seems to change that help screen. If I hit the ESC key I actually "drop" to cp/m - and can do a DIR of the B drive, change to the B drive, and run xdir on the Utilities disk in the B drive.

Reading the manual, I now remember that the Help screens are the "initial menu" when cp/m is loaded.

So it seems there's something hanging in that Help section. By the way, I tried this with a second (backup) system disk, and get exactly the same result.

This is progress - just not very far down the road.

Does this "hanging" in the Help system indicate anything obvious to you experienced folks?

Thanks.
Tom

dave_m
August 5th, 2009, 07:20 PM
If I hit the ESC key I actually "drop" to cp/m - and can do a DIR of the B drive, change to the B drive, and run xdir on the Utilities disk in the B drive.


This is great news that you discovered ESC gets you to the system prompt. At this point perhaps you should try to test your RAM. Do any of your floppies contain a memory/RAM test or some diagnostics? Also before you get too far, you should check the +5V power to ensure it is well regulated and with minimum ripple/noise.

tezza
August 6th, 2009, 12:57 AM
Hi Tez - there's a goodly number of ram chips and capacitors on the board. How did you find the faulty one? As they're soldered in, I'd imagine they're not all that easy (!) to trace and replace.

Tom

Well, regarding identifying faulty RAM I used the old hardware hackers technique of piggybacking a good RAM IC over each RAM on the board, switching on and seeing if it made any difference. Whether it works with faulty RAM depends very much on the nature of the fault in the IC itself. It worked that time for me though.

More about it (and other Ozzie repairs) here (http://www.classic-computers.org.nz/blog/2008-12-06-osborne-repair-1.htm) (halfway down the page).

Tez

NutmegCT
August 6th, 2009, 03:17 AM
Aha! Now we're getting somewhere - a memory test.

I can borrow a ram test on a double-density disk. I also have an Osborne friend who can lend me pair of double density disk drives, and a double density card.

What do I need to do to change my OCC1 to double density? I see where to put the DD card on the logic board, and where to put that short cable that goes from the DD card to the main board. Are there other changes needed? Any jumpers to change? Does another chip need changing? My two ROM chips say "Rev D" and "REV 1.4 7/26/82" (one in my original OCC and one in this "replacement" OCC).

Thanks.
Tom

dave_m
August 6th, 2009, 12:28 PM
Tom,
I'm not sure that you should make so many changes to the current configuration until you know more about the problem. Can your friend make a single density copy for you with the test program on it?

If not, there are plenty of other things to check. You should make sure you have good clean +5V and also check the DC power to the disk drives. Keep a good log of all changes that you make so that you can return to the original configuration if necessary.

NutmegCT
August 6th, 2009, 01:05 PM
Dave - he's got the drives and the card, but doesn't have a working Osborne. So, unfortunately he can't make a single density disk for me.

I did, however, get the two DD drives and DD card (and cable) installed, and along with the 1.4 ROM chip I've now got a working DD machine. Still has the same boot problem, but now I can boot from a double density Osborne system disk.

Symptom remains: Power on, screen asks for system disk. Insert system disk and hit Return: screen shows Loading CP/M and disk reads. Screen changes to top two lines reading "Osborne Computer and Help 2.1", then hangs there, with various random graphic characters slowly appearing on the screen.

I tried the original single density drives and boot sequence this morning after a long night of rest for the Osborne. No change at all, so it seems that heat has nothing to do with the problem.

I'm really feeling this is a RAM problem (boot, drive, video weirdness) as others have described. But 'til I can get a clean boot again I can't load that diagnostic disk. And of course, Osborne discontinued the built-in diagnostics when they started using ROM 1.3. Used to be you could hit CTRL+D at the "insert system disk" prompt. No longer.

I am making progress - but now have to figure out how to troubleshoot faulty RAM chips.

Edit: Dave - where exactly do I check for that +5V? I do know that the PSU is putting out +5V - if that's what you mean? Thanks.


Onward through the fog!
Tom

NutmegCT
August 6th, 2009, 01:50 PM
Gents - an update with good news.
I found one of my old DD disks from the early '80s. It was marked "Diagnostics SYS" on the label.

I figured that SYS meant that I had put the cp/m OS on that disk along with whatever the diagnostics were. I put the disk in A, powered up, hit Return when the screen asked, and voila!

I got a clean boot - with NO help screen or garbage. I'm now running a FOG utility called MemTest. I don't have any docs on that app, but I'll report back after it's finished.

So far - 5 minutes into the run, screen shows 4139 refresh failures in something called Location UB - 27. Have no clue how to interpret that.

Stay tuned.
Tom

NutmegCT
August 6th, 2009, 02:38 PM
OK - final result of the memory refresh test: no failures *except* Location UB:27. That location had 99999 failures (I assume that's not good).

So, looking in the OCC Tech Manual, and reading that memory is physically located on the logic board in four ranks (UA, UB, UC, UD) with eight files (20 - 27), I *assume* that the eighth chip in the second rank is the failure.

Could someone confirm I'm interpreting this correctly?

If so, I assume that the next step is to replace that chip. I have plenty of extras - from my original Osborne's logic board. I'd need to figure out how to remove a chip, and how to insert it to replace the faulty one in my replacement board.

Thanks.
Tom

dave_m
August 6th, 2009, 03:40 PM
Very good. Yes I think you have the right chip location. The system board may have some markings to confirm the IC locations. The chip in question seems to be a dynamic RAM meaning it needs to be refreshed (read out) once in while by the system hardware to maintain its data contents. It seems that chip at UB27 is not retaining its data. Hopefully the chip is in a socket. If not, you will have to remove it. After that you may want to install a chip socket to make it easier to install the new chip. What type of RAM chips does the Osboune use? Is it a type 4116 (16K X 1) or similar?

Are you good at soldering? If you are not an experienced hand at soldering, I would advise you to play it safe. By that I mean it may be better to cut all the leads off towards the top of the chip before you attempt to unsolder the individual leads from the system board. This will reduce the amount of heat necessary to unsolder each lead.

Others on this forum can explain better than me about the use of solder wick, solder suckers and other aids to remove the leads and clean the plated through holes on the system board.

tezza
August 6th, 2009, 03:40 PM
Tom,

Sounds like you're making progress. A RAM problem could certainly account for all those weird problems. It looks like you've identified the correct IC but I'm not really an Osborne guru and it would be good for someone who is to comment. You don't wnat to be pulling out the wrong IC.

For desoldering ICs I've found solder wick works well for me. However, it's easy to damage the tracks around the IC when extracting chips from spare board to place in working ones. This is no problem if it's a junk board but if you want to keep it as a possible "good" spare, I would see if you can source a replacement from a junk board or the net. From memory they are 4116 ICs yes? These were common in many machines of the era.

To extract the faulty IC, just carefully clip each pin off the the chip then extract the pins one at a time using a soldering iron and pliers. Use solder wick to clean up the holes.

Similar to what I did for my IBM PC as described here (http://www.classic-computers.org.nz/blog/2009-03-18-ibm-pc-ram-repair.htm).

Tez

dave_m
August 6th, 2009, 03:46 PM
Tom,
Before you unsolder the chip, carefully examine the solder joints on that chip with a magnifying glass in a good light. If you see a joint that is not shiny, it may be a cold solder joint that is making intermitent contact. Reflow the solder joints to make good connections.

dave_m
August 6th, 2009, 04:05 PM
You don't wnat to be pulling out the wrong IC.

For desoldering ICs I've found solder wick works well for me. However, it's easy to damage the tracks around the IC when extracting chips from spare board to place in working ones. This is no problem if it's a junk board but if you want to keep it as a possible "good" spare, I would see if you can source a replacement from a junk board or the net. From memory they are 4116 ICs yes? These were common in many machines of the era.

Similar to what I did for my IBM PC as described here (http://www.classic-computers.org.nz/blog/2009-03-18-ibm-pc-ram-repair.htm).

Tez

Tez, that's good advice from a guy who has proven he can do it. As for myself, I usually make a ham-fisted muck of such repairs.

NutmegCT
August 6th, 2009, 08:36 PM
Gentlemen - your advice and encouragement are priceless. Thank you.

All RAM chips are soldered into the board.

The "bad" chip is marked NEC D416C
The replacement (same position on the other board) is marked AM9016FPC 8228GMP

Is that a match?

T.
PS - by "piggybacking" do you mean simply holding one chip over another so all the upper chip's legs touch the lower chip?

cosam
August 7th, 2009, 12:37 AM
The "bad" chip is marked NEC D416C
The replacement (same position on the other board) is marked AM9016FPC 8228GMP

Is that a match?

It would certainly appear so; both are 16K x 1 DRAMs and being used in the same places on similar (identical?) boards is a good sign.

I would however second Dave's tip of reflowing the solder first, especially as the thing was working not long ago and only started playing up after that long drive.

It's of course up to you, but if it does need replacing, I'd suggest tracking down a loose replacement RAM chip, unless the donor machine is a complete write-off. Removing an IC from a board intact can be tricky. If you do decide to do it, it's worth practicing on a junk board first. There are some tips on the wiki (http://wiki.vintage-computer.com/index.php?title=Desoldering_ICs).


PS - by "piggybacking" do you mean simply holding one chip over another so all the upper chip's legs touch the lower chip?
That's the way, yep. Incidentally also on the wiki (http://wiki.vintage-computer.com/index.php?title=Piggybacking) ;-)

NutmegCT
August 7th, 2009, 03:57 AM
Cosam - thanks very much for all the pointers.

You mention "reflow" - I can't find that in the wiki. Does that mean letting a bit of solder flow down on each pin? Or does that mean just touching a hot solder iron to each pin to "re-set" what's there?

I can't see any non-shiny solder points under that chip - which I think is what Dave was referring to in his reflow suggestion.

Thanks.
Tom

cosam
August 7th, 2009, 04:19 AM
You mention "reflow" - I can't find that in the wiki. Does that mean letting a bit of solder flow down on each pin? Or does that mean just touching a hot solder iron to each pin to "re-set" what's there?
You'd probably get away with just melting what's there and let it solidify, although feeding in a touch of new stuff will often help the old solder flow more nicely, giving you a better joint.


I can't see any non-shiny solder points under that chip - which I think is what Dave was referring to in his reflow suggestion.
A non-shiny ("dry") joint would definitely suggest a problem, but it's not always all that obvious. As reflowing a few pins is so quick and easy, it's worth a try. Worst case scenario: you need to replace the chip after all. Even then reflowing wouldn't be a complete waste of time as the "fresh" solder will likely be easier to remove than old stale stuff.

NutmegCT
August 7th, 2009, 05:09 AM
Touched a hot electronics iron to each solder point (under the board) on that chip. Saw the solder "melt" and quickly moved away.

Ran the entire memtest series (refresh, galpat, v-bar, diagonal) again. Results:

Refresh - 4799 errors
Galpat - 25188 errors
V-bar - 14706 errors
Moving Diagonals - 4027

And all the errors are at board location UB:27.

Also did a "continuity" test between similar pins on the UB:27 chip and other chips. Continuity all good - which to me means there are no breaks in the circuit at the tested points.

So my beginner's brain says there's a problem in the chip at the UB:27 location. And my brain also asks: Is there a way to simply "lock out" that failed chip from use?.

Again, it's obvious I'm new to all this. Is there any other test I should do before trying to remove the failed chip and solder in a replacement?

Thanks.
Tom

cosam
August 7th, 2009, 05:40 AM
So my beginner's brain says there's a problem in the chip at the UB:27 location. And my brain also asks: Is there a way to simply "lock out" that failed chip from use?.

Again, it's obvious I'm new to all this. Is there any other test I should do before trying to remove the failed chip and solder in a replacement?
Sounds pretty definitive to me. I'd go ahead and replace the chip at UB:27. Even if you did somehow lock the chip out, you'd be missing one bit from every byte in the 16Kbyte it's part of, which I don't think will get you very far ;-)

dave_m
August 7th, 2009, 07:41 AM
Tom,
I'd hate to see you have to rob parts from a vintage Osborne board that might be fixable later.

I recently repaired a Commodore PET which had a bad 4116 RAM chip. I have some left over chips and 16 pin sockets. Send me a private message to me (dave_m) on this forum with contact info so I can send you the needed parts.

NutmegCT
August 7th, 2009, 07:45 AM
OK - here goes. I'm heating up my iron to remove a good chip from my spare m/board. This is the board that won't boot up at all - just a garbage screen. I may have to remove several of those chips for a piggyback test, 'til I know I've got a good one.

Question: How do I remove a good chip? I understand the removal of a bad one: cut off (I assume with a Dremel and a cutting wheel) each leg of the bad chip, then de-solder each leg separately from the m/board so I have spot with empty holes.

But I'm pretty foggy on removing a good chip, i.e. whole. Do I somehow work on the underside of the board, heating each pin bottom 'til the solder "falls" out? Then when all have "dropped their solder", turn the board over and tap the chip out?

It seems that de-soldering from above would just melt the solder back into place, as I can't see how to "pull" the chip up with all the rest of the pins still soldered in place.

I did check the Wiki and other links, but they seem to concentrate on removing a *bad* chip - not on removing a good one.

Thanks.
Tom

NutmegCT
August 7th, 2009, 07:51 AM
Dave - I just sent you a PM.

barythrin
August 7th, 2009, 08:03 AM
Yup, that's the right concept on piggy backing a chip. er.. ok I replied to the last post on page two. Nice. Anyway, I'd suggest getting a desoldering iron http://www.radioshack.com/product/index.jsp?productId=2062731, I know there are solder suckers but they're a little more of a pain to use. This one is nice although you do have to be careful not to burn the traces or PCB.

Alternatively if you can push the solder around and away from the pins/hole you can sometimes use some non-rough screw driver action to get the chip off the board. I suppose some folks would cut the legs but I'm not big on that since fresh solder and connection joints would be the ideal situation. It'd be ashame to solder a new dip onto old legs and bad solder joints.

dave_m
August 7th, 2009, 08:30 AM
I suppose some folks would cut the legs but I'm not big on that since fresh solder and connection joints would be the ideal situation. It'd be ashame to solder a new dip onto old legs and bad solder joints.

That's not quite what we meant. One cuts the legs away from the body with a small diagonal cutter tool. This allows one to unsolder the legs one at a time without overheating the board. You then clean the holes with solder wick before one installs the new chip.

tezza
August 7th, 2009, 01:17 PM
Question: How do I remove a good chip?

Tom,

In your case there are two things you want to do....

1. Removing the faulty ram. Clip the legs off the IC, using fine snippers then desolder each leg from the board one at a time. After they are removed, clean up around the holes with solder wick.

2. Extracting a good IC from the second board.

This is tricker than 1.

I've used solder wick for this. Do a leg at a time. Start from the back side of the board where the pin protrudes out. Press the solder wick against the solder on the pin. Put the hot iron on the wick until the solder flows into the wick (you'll notice when this happens). On the first attempt, you probably wont get all the solder but don't hold the iron there too long. Just a second or two. Cut off the used wick and try to collect more solder with another attempt. Work through all pins. Then flip the board over and do the same thing with the legs as they go into the board as there is probably a little solder around them too.

Then you'll probably need to revisit the bottom of the board again and maybe the top too. Once you think you've got all the solder, get the edge of a screwdriver under the IC and just gently try and lift it. Don't force it. If it doesn't move, there is still more solder to remove.

It's laborious, exactling and takes a long time.

I would strongly, strongly advise you to try this first with both a board and an IC you don't want just for practice.

I would also advise that you don't use your other Osborne board as the source unless you are SURE you want to turn it into junk board. A good Osborne board is probably salable. If it shows garbage characters then it may be simply a single RAM IC which needs replacing on that board. This was the case with mine. You may find you soon have the skills to repair it.

All the IC's I've removed for REUSE (hence I extracted rather than just clipping them off) have been from junk boards. Hence my only concern was the IC, not the board or the tracks. Unless you are very skilled and have all the right tools, its almost impossible not to wreck the board when you are trying to extract a chip. You will probably destroy a good Osborne board which only needs a single IC replacement.

It's up to you, but if it was me, I would take up Dave_m''s offer even if it meant waiting a few days for the chip to arrive.

Good luck anyway

Terry

NutmegCT
August 7th, 2009, 01:31 PM
Terry - this is excellent. Thanks for the detailed instructions.

I've contacted Dave and hope to receive the items I need in a few days. I had figured that the first board was pretty much useless; as I didn't have a way to test/diagnose/repair it, I thought it was usable for parts only. Thus I used the 1.4 ROM from it to replace the 1.3 on my working board, and was able to make the working board functional for double density. Now I'll have that non-working board relatively untouched - and may be able help someone here one day.

Have a good weekend everybody. I'm an 1830s New England farmer at Old Sturbridge Village on Saturdays and Sundays; great retirement job if ever there was one.

Tom
www.osv.org

NutmegCT
August 12th, 2009, 02:30 AM
Wednesday update: Yesterday I got two new 4116s and sockets. I tried the piggyback test. With the original chip, I was getting about 4000 refresh errors in a cycle of refresh tests (FOG diagnostic disk). With the new chip pressed down over the old chip, I got about 700 refresh errors on that same testing cycle. The diagnostic still indicates the error in exactly the same location as before I piggybacked the chip - UB:27.

Removed the replacement, and tried the second replacement chip. Pretty much the same result: much fewer errors than before piggybacking, but they're still in the same location.

Obviously a new chip makes a difference. But I had (naively?) thought the new chip (piggybacked) would eliminate all errors.

Does it still seem that replacing that original chip will end the problem? Should I go ahead and remove it, put in a socket, and add the new 4116? Or is the continuing (but reduced) error problem evidence that the new replacement chips are faulty also? or even that there's still another problem?

Paranoid in Connecticut.
Tom

cosam
August 12th, 2009, 02:55 AM
I think we can safely establish that the original chip has had it and needs to be replaced, so I'd go ahead and do that. Piggybacking won't uncover every kind of fault, but the fact that it made any difference at all is encouraging. If you're lucky, the RAM replacement will be all that's necessary (and even if it isn't, it most likely needed doing anyway).

dave_m
August 12th, 2009, 07:31 AM
Tom,
I agree with cosam. With piggybacking, one is only looking for a change for the better. It is difficult to maintain 16 solid connections with this technique for the entire test.

NutmegCT
August 12th, 2009, 07:45 AM
11:42am EST update:

Carefully clipped off the pins of the faulty chip. Using copper wicking, got about half of the board holes cleaned of solder. But there are a few holes where the solder is just inside the hole - in other words, not flush with the surface top or bottom.

Could someone give me a pointer on how to get that tiny bit of solder out? I've been using my 25w iron and the copper wicking, but the solder in the hole isn't touching the wicking - so there's no heat transfer. I'm sorely tempted to try to drill it out with a Dremel, as poking it with a needle or toothpick isn't successful.

Thanks. Seems I'm 90% there.
Tom

cosam
August 12th, 2009, 09:28 AM
Just drop a bit of new solder in/over the hole and you should be able to pull the old stuff out with it.

dave_m
August 12th, 2009, 10:30 AM
Tom, please follow cosam's advice. Do not use a drill as you might damage the plated-through hole and printed circuitry. Solder wick works by capillary action and so the wick must be in contact with all the solder.

I do not know if you have removed the system board from the chassis. If so you can always try to remove the solder by working on the flip side of the board.

NutmegCT
August 12th, 2009, 01:12 PM
I used Cosam's advice and dropped a bit of solder on each of the problem holes. Finally got the problem holes cleared; sure seemed there was some mighty persistent solder down in a few of those holes, so I had to do several cycles of the "solder drop and wick" bit.

Checked for continuity to the adjacent IC to be sure there was no damage - all OK. Carefully laid in the socket and soldered each pin. Checked continuity again. Carefully pressed in the new IC and checked continuity to adjacent IC.

Reinstalled all the lines, plugged in the power cord, girded my loins and flipped the red power switch.

Silence.

Not even a beep.

Totally flustered on this. I've checked all the lines - can't see anything I'm forgetting. Again checked continuity of new IC and adjacent IC. Even removed the new IC and left the socket empty.

Still total silence on power. Fuse ok. Power up but no drive light, no CRT filament.

If I've now got a working system board, but the PSU has just decided to give up the ghost, I'm not a happy camper.

Geez Louise.
Tom

NutmegCT
August 12th, 2009, 01:51 PM
The fun continues. I disconnected every cable from the logic board, removed it. Decided to test the power outputs (5v, 12v) from the PSU.

Plugged into wall, flipped red power switch - flash, zap, smoke and sparks from R5 on the PSU. R5 is a 1K half watt resistor. Powered off immediately. Said a few choice words.

I cannot believe this is all happening - especially when this morning I could boot up the system fine (altho' with faulty ram). Now I've got the ram replaced, and the fog has descended once again.

T.

dave_m
August 12th, 2009, 04:38 PM
Tom,
Some of these old power supplies do not like to run into an open load. Let's wait to hear from the power supply experts before trying anything else.

From the smoke and flash, I'd guess you will be replacing the big electrolytic capacitors. They would have blown sooner or later.

Power supplies can be fixed. Try to hang in there. One day (in the future) you will be laughing as you tell of this adventure.
-Dave

tezza
August 12th, 2009, 05:09 PM
Yes, don't give up Tom. My Osborne required me to deal with three separate issues and it sounds like yours is heading that way too.

I doubt if the RAM fix would have contibuted to this latest problem unless you plugged something in incorrectly. I'd also go for the big electrolytic cap theory. One thing with exploding caps...you can always tell which component has failed.

Keep at it. As with me, you'll be learning a lot doing this, knowledge you'll use for other vintage repairs.

Tez

NutmegCT
August 12th, 2009, 05:20 PM
Thanks for the encouragement gents.

Maybe a failing PSU was part of the mix all the while. You both mention replacing the electrolytic caps. Altho' I didn't want to have to chase all that down after spending over $150 - and a week - to get the "new" OCC ... note that the part that fried today was a resistor, not a capacitor.

I have replaced that resistor, but still no luck. System still dead.

Is the PSU one of those "serial devices" that, if one part (e.g. the R5 resistor) fails, other fall like dominos?

Thanks.
Tom

dave_m
August 12th, 2009, 10:17 PM
I would not re-connect the PSU to the main board or CRT until I was sure the power supply is fixed. This probably means hooking up a load box to the PSU. This box will consist of high wattage resistors to present the proper nominal loads to the secondary power (+5V, +12V, etc). With power off, you can also check for opens and shorts of the various components. Hopefully a good power supply troubleshooter on this forum can give you a safe plan of action. Go slow and don't hurt yourself. Do you have a schematic of the PSU?

cosam
August 13th, 2009, 12:35 AM
Do you have a schematic of the PSU?
Knock yourself out (http://www.vintage-computer.com/vcforum/showthread.php?t=16552) ;-)

BTW, if I'm reading this correctly, R1 should be some kind of thermistor - is that right?

NutmegCT
August 13th, 2009, 02:34 AM
Yep - I already got all those schematics, including the PSU. As I have no way of testing capacitors (other than for continuity) it seems all I can do is pull every single cap and replace it. Oy.

Steve, yes, R1 is a 4 ohm thermistor.

I don't have a clue about constructing a "load box", so I'll have to replace all the capacitors today if I can find them at RadioShack. No other resistors have blown, so I won't touch any more of those.

Tom
PS - in this PSU, are capacitors just "capacitors"? In other words, as RS has a limited parts selection these days, can I replace an electrolytic with a ceramic, ceramic with poly, vice versa, etc., if the Farad rating is equal, if need be?

PPS - is there something in the PSU I might be overlooking? Here's the scenario: (1) system worked fine, but with a failed ram chip. (2) removed logic board, replaced chip, put all back together, powered up - no beep, no drive action or CRT filament light. (3) removed PSU, powered up, resistor exploded. Seems there was something really *basic* that happened to that PSU - and it happened before the resistor exploded (when the PSU had no load).

cosam
August 13th, 2009, 03:16 AM
Yep - I already got all those schematics, including the PSU.
Thought so - it was more for the benefit of others.


Steve, yes, R1 is a 4 ohm thermistor.
Ah, sorry - I was looking at the schematic wondering what could make that blow, but looking back it was R5 that went. Don't know where I got R1 from, so ignore that ;-)


PS - in this PSU, are capacitors just "capacitors"? In other words, as RS has a limited parts selection these days, can I replace an electrolytic with a ceramic, ceramic with poly, vice versa, etc., if the Farad rating is equal, if need be?
Not just the capacitance but the voltage rating must be equal to (or greater than) the original. Depending on the application, polarisation - or indeed lack thereof - may or may not be important, too. Whilst substitute parts of different types would probably work in some cases, you may have trouble finding parts which will physically fit (or even exist at all) if using very different types, especially when it comes to high capacitance/high voltage capacitors. Best to stick with the same types of parts wherever possible. If available values are very limited, using two or more capacitors in series or in parallel will give you some leeway, although it can get messy and you may of course run into space issues.

NutmegCT
August 13th, 2009, 11:49 AM
Feeling a bit overwhelmed here. I stopped at RadioShack and found they don't carry any 250v 100mF capacitors; there are two on the PCB. I assume those are the first electrolytic ones I should replace as they're at the high voltage end?

RS does have some of the lower voltage caps I need, but the leads on those are at opposite ends; the PCB uses "vertical mount" caps with leads that are about 1/2" apart on the board, so to use those RS caps, I'd need to have a *long* extended lead from the top looping down to the board.

Of course, their internet connection has been dead all day, so they couldn't check their supplier. As I don't have a way to test the caps, I assume it's safer to replace them but now I guess I need to find another source.

Came back home after no luck at local electronics/radio shops. Decided to test the resistors on the PCB. Per schematic, R2 should be 330K ohms: orange orange yellow gold. Test on digital VOM shows 2M ohms, slowly dropping to 120K. Per schematic, R3 should be 220 ohms (red, red, brown, gold); test shows 179 ohms. However, that resistor is a solid green cylinder - no color bands. Same for several other resistors - are there resistors that are a single solid color?

Man, talk about the blind sailor in a storm, with no compass and just guessing which ropes he's pulling!

I again assume that if the test resistance shows a significant variance from the schematic, that resistor should be replaced.

Getting frazzled by the minute.

Thanks for your patience.
Tom

dave_m
August 13th, 2009, 01:06 PM
Tom,
I had a look at the power supply schematic. Wow, it looks like a fairly sophisticated switching power supply. I am not the right guy for this. I hope others jump in.

The Sams documentation calls out the power supply parts list. You will need to take this to an electronics components place that handles these types of parts. Can you find out if you have the local equivalent to this kind of place: http://www.orvac.com/index.html and buy direct equivalent parts that fit especially the capacitors.

Remember, as you are measuring the resistors “in-circuit”, there are components in parallel with it which would normally reduce the reading. The reading of a resistor can never be higher than its listed value, but can be lower. More importantly than the value being off a little, if it looks charred or discolored or the circuit board under it looks discolored, you should change the resistor. They usually fail open or short.

From what you say, the R2 resistor look suspicious. R3 on my schematic from cosam says 180 ohms, 1 watt. Is your version different?
-Dave

NutmegCT
August 13th, 2009, 01:16 PM
Hi Dave - Maybe you've discovered part of my problem already. I'm using the "Repair Manual for Astec Power Supply 8151" - which is what mine is labeled on the PCB.

The manual shows R3 as 220R (ohm), +/- 5%, 1 watt.

When you say "my schematic from cosam" do you mean from SAM's? Or is this something you got from Steve (cosam) here?

Yikes - should I be using a different schematic?

Tom

dave_m
August 13th, 2009, 02:35 PM
Hi Dave - Maybe you've discovered part of my problem already. I'm using the "Repair Manual for Astec Power Supply 8151" - which is what mine is labeled on the PCB.

The manual shows R3 as 220R (ohm), +/- 5%, 1 watt.



There may be slight differences from the schematic I'm looking at that cosam pointed me too from his message earlier today. You replied to him that you also had the Sams Photofacts documentation.

I did not realize the power supply was a commercial unit (Astec). Have you started to look around for a working unit? Are they expensive? Of course as you now have two bad units, if you learn to fix one, you can also fix the other.

Did you check out tez's link to how he fixed his Osborne? http://www.classic-computers.org.nz/blog/2008-12-06-osborne-repair-1.htm

NutmegCT
August 13th, 2009, 03:14 PM
Other than that R3 discrepancy, the two documents seem the same. I just pulled the R2 and replaced it with new. No change at all in boot-up, drive action, etc. Spending an hour and second-guessing myself at every step, just to pull and replace a single resistor, then having no success, is pretty discouraging.

I've been keeping an eye on Astec Osborne PSU's on ebay. Last week there was one for $69 plus $15 shipping, but it's "as is". A couple days ago there was another for $55 described as "working - looks like new". This morning the price got raised to nearly $100. Weird.

I've now spent two weeks learning a lot about electronics, and about myself, and have pretty much concluded that this is way beyond my ability and patience. An electronics shop in Hartford told me they'd be happy to bring the PSU up to spec, but it would be $65/hr, minimum 4 hours.

Not looking good. Really wanted to bring my original OCC back to life; it sure has some good memories from my college days. I started 2 weeks ago with my original OCC which wouldn't boot and showed screen garbage. Diagnosed the PSU failure. Paid over $150 for another OCC - which I actually saw running SuperCalc - and somehow managed to nearly reduce it to rubble. I've got parts and gear all over the place. Man this is a downer.

T.

dave_m
August 13th, 2009, 09:21 PM
I've been keeping an eye on Astec Osborne PSU's on ebay. Last week there was one for $69 plus $15 shipping, but it's "as is". A couple days ago there was another for $55 described as "working - looks like new". This morning the price got raised to nearly $100. Weird.

$100 bucks for an unknown power supply seems too much. And $260 to repair is too much. Before you give up, think about taking the power supply and the documentation to the engineering department at your local junior college and asking if they will take the repair on as a lab project if you pay for the parts. There will be no guaranties, but it may be worth a try.

For not being an electronics guy you have showed a lot of moxie for attempting this fix. I really wish there was better results.

NutmegCT
August 14th, 2009, 03:48 AM
OK - one last dying gasp ... You recall I had replaced the paper caps in my original PSU. Connected it and powered up. System beep, A drive briefly lighted; this is "normal". But the screen was still garbage (a single graphic character filled all the lines). This is *after* I replaced that ram chip.

If all is well on that PSU except some aspect of video feed, is there a way to tell what part needs replacing now?

At least my first repair - on my original PSU - doesn't result in a totally dead system. It's like only the video is now flakey.

As an aside, trying to describe a sequence of events, and individual details relating to those events, is quite a challenge!

Tom

NutmegCT
August 14th, 2009, 05:47 AM
Put in my original PSU with the new caps (that replaced the original fried paper caps). Cabled up, powered on, system beeped, A drive clicked, screen is that single garbage character throughout. No response to System disk and hitting Return.

I then checked the output voltage from both output jacks on the PSU: voltage seems correct. Top pin is -12.5v, next is +12v, next is Common, next is +5v. This seems spec to me - as schematics show -12v, +12v, Common, +5v.

Need to determine why the video display is screwed up. Keeping in mind that the video was *not* faulty with the "new" PSU (when it was working).

Also, it seems it's not just a video problem, as the system doesn't seem to be starting from ROM; it doesn't respond to insertion of System disk and hitting Return.

Tom

NutmegCT
August 14th, 2009, 06:23 AM
BOOT! (almost)

I replaced my PSU cable with the PSU cable from the "replacement" PSU. My original was a dual-cable, with two four-pin sockets at PSU running to a single socket plug for the logic board. My replacement PSU had a single four-pin socket running from PSU to logic board (with a "jumpered" logic board socket).

Powered up - beep, drive click, and SCREEN IS CORRECT. Asked for system disk, I inserted and hit Return. BOOT ERROR repeatedly scrolls down screen.

Powered off, put the original dual-plug cable back on PSU, restarted, and screen is back to garbage. Put in the single plug cable, and system seems fine (and screen is perfect) until I hit Return for the disk read; that gives BOOT ERROR.

It's got to be something in the "mesh" between PSU to logic board to drive board.

Back to more monkeying ....

T.

NutmegCT
August 14th, 2009, 06:54 AM
BOOT!

I moved that single cable to the 3rd jack on the PSU. That's the one shown as unused on all the schematics, but it outputs the same voltages as the other two.

I have no clue why ... but the system booted properly from the A drive disk, giving me an A> prompt.

I was then able to load dBase 2.41 from the A drive. Even remembered a few of the old dBase dot prompt commands. Senility hasn't totally taken over yet.

Now I'm trouble shooting why I frequently get "bdos error; sector not found" on attempts at disk access on A and B drives. I'm betting it's still a voltage problem to the drives. Maybe that single cable won't serve a dual density drive setup?

T.
PS - I booted from the original OCC1 system disk, with the help files. It ALL LOADED - didn't freeze up. Looks like replacing that ram chip actually worked. Yeehaa!

cosam
August 14th, 2009, 07:17 AM
Not sure what's up with your drives (are the heads clean?) but congratulations on getting the thing running! I'm glad you stuck at it and weren't afraid to tinker. For a moment there, I was afraid it was going to get the better of you!

NutmegCT
August 14th, 2009, 07:19 AM
Screwed the boards back to the chassis, and turned it right side up. Didn't change anything else from previous post.

Powered up, and get opening screen "please insert disk" but nothing but BOOT ERROR whether I try booting from A or from B drive.

This has *got* to be a power problem; wonder if the dual density drive system just uses more power? And that single cable isn't providing enough?

T.

dave_m
August 14th, 2009, 07:50 AM
Tom,
You are probably fighting an intermittent connection. This is hard to check in a tight assembly like the Osborne. Go slow and keep a detailed log of everything you do so you can keep track of things.

I found an Osbourne Field Service Manual on the web. Do you have it?

NutmegCT
August 14th, 2009, 07:57 AM
Dave - is that the "Preliminary Service Manual? from SAMS? It's 6 pages long? I've got that, as well as the Osborne I Technical Manual (586 pages), the SAMS Board, Drives, and Monitor schematics, and that Astec PSU manual.

What's the location of the Field Service Manual you found? Edit: I did find a "field service manual" at kev.pulo.com.au, but it starts at Chapter 6 and only covers assembly/disassembly.

After lunch I'm going to see if lightly "flexing" that logic board makes any difference. It seems the only thing that would be "different" when I turned the unit from upside down to rightside up.

T.

dave_m
August 14th, 2009, 09:24 AM
Tom,
It's probably close to the technical manual but has very good tips on repairing and what to look out for. You should review this carefully. I can't find it again after a web search, but I did make a copy of the pdf file.

1983_Osborne_Field_Service_Manual.pdf (http://home.att.net/~betty.p.mercado/Old_Test_Equipment/1983_Osborne_Field_Service_Manual.pdf)

Make sure you heed recommendations like "Be sure there is a 1 in. Length of doubLe-backed tape covering the "y" pattern on the soldered-side of the Power Supply."

Also make sure screws are not to long and touch things underneath that they should not. Before you reconnect connectors, examine then for bent or broken pins, etc.

dave_m
August 14th, 2009, 10:04 AM
The manual also states that many of the connectors on the Osborne are not keyed and can be easily plugged in wrong. Wow be careful!

NutmegCT
August 14th, 2009, 10:14 AM
Definitely agree on that "intermittent problem" -

After my one successful boot, I've now had:

BOOT ERROR after trying system from A or B drives, followed by one or more of the following:

screen flashing on and off
high pitch squeal (board? drive?)
"clicking" two or three times from drive (?)
random drive activity

After the successful boot and run with system inverted, I had righted the system and got the BOOT ERROR message.

Then tried restarting *while lightly lifting up on logic board, center at edge*. System again booted and ran perfectly.

But a repeat of the same lifting action wasn't successful second or subsequent times.

Still get BOOT ERROR from whichever drive I try to boot from.

Puzzling.
T.
PS - thanks for the pdf file Dave. Downloaded it from you.

NutmegCT
August 14th, 2009, 10:21 AM
And of course, here's a new twist. I just switched the single plug cable to the middle jack on the PSU. System actually ran fine, loaded system and all help files, even read dir of B drive.

Tried loading dbase from B drive; got "bdos error"

Reset system. Tried booting exactly the same way (A drive); got BOOT ERROR.

Edit: how can I clean the drive heads w/o a cleaning disk? Can I just put 70% isopropyl alcohol on a q-tip and carefully rub over the head inside? (if I can reach the head?)

dave_m
August 14th, 2009, 11:23 AM
Definitely agree on that "intermittent problem" -

After my one successful boot, I've now had:

BOOT ERROR after trying system from A or B drives, followed by one or more of the following:

screen flashing on and off
high pitch squeal (board? drive?)
"clicking" two or three times from drive (?)
random drive activity



This is not good! It may mean possible shorting of power to various subsystems. With too much shorting the power supply may be damaged. You are in a difficult position. With the system buttoned up, it is hard to troubleshoot, but opening the system may make the symptons go away.

Think carefully about what you want to try next. Do not be rash. You are too close to getting this thing to work.

I'd like to hear from others but I would consider a very careful inspection of the power harness and connectors. Do you know how to ohm-out cables for proper connections?
-Dave

tezza
August 14th, 2009, 11:34 AM
This is not good! It may mean possible shorting of power to various subsystems. With too much shorting the power supply may be damaged. You are in a difficult position. With the system buttoned up, it is hard to troubleshoot, but opening the system may make the symptons go away.

Think carefully about what you want to try next. Do not be rash. You are too close to getting this thing to work.

I'd like to hear from others but I would consider a very careful inspection of the power harness and connectors. Do you know how to ohm-out cables for proper connections?
-Dave

Not good at all. The fact it worked when flexing the board a little suggests a connection problem somewhere (dry solder joint etc.). These are the most frustrating of problems.

Tom, consider also that the boot problems may have zapped your disk. This happened to me with my osborne when I had the drive problem (http://www.classic-computers.org.nz/blog/2009-04-03-osborne-drive-fix.htm)(which was also intermittent). When the machine crashed, the drive lights often flashed on and off, screen became garbage and random beeps occured. And on occasions the disk was toast, even though it was read-only.

Make sure you have plenty of backups.

Tez

NutmegCT
August 14th, 2009, 11:36 AM
"Do you know how to ohm-out cables for proper connections?"

Just guessing again, but doesn't that mean to check for continuity? (I've actually done that for the power cable, both the single-jack and the double-jack cable. All tests for proper continuity.)

Or does that mean something on a higher level, like checking the resistance between specific pins for specific ohm readings?

By the way, that BOOT ERROR is the same message I get if I try to boot from an empty drive. The drive spins but the system thinks there's no disk there.

Edit: Just read Tez's post. I've tried the boot with several boot disks. Can boot maybe one out of twenty attempts, using various boot disks, after a power cycle on/off.

tezza
August 14th, 2009, 11:38 AM
Did you try another copy of the boot disk? (see above).

Tez

dave_m
August 14th, 2009, 11:45 AM
"Do you know how to ohm-out cables for proper connections?"

Just guessing again, but doesn't that mean to check for continuity? (I've actually done that for the power cable, both the single-jack and the double-jack cable. All tests for proper continuity.)

Or does that mean something on a higher level, like checking the resistance between specific pins for specific ohm readings?



No, that's what I meant. Did you inspect the pins for corroded, bent or broken pins? Both on the harness and on the system board?

NutmegCT
August 14th, 2009, 11:49 AM
"Did you inspect the pins for corroded, bent or broken pins? Both on the harness and on the system board?"

Yep - did that early on. Really very clean and dust-free inside. All pins shiny.

I agree that it could be an almost-invisible crack or solder joint problem on the system board. But as everything so far has been "random and intermitten" it's frustrating.

Going to let it cool power off for another 30 minutes, then try the boot process again.

T.

NutmegCT
August 14th, 2009, 12:09 PM
OK - one step at a time.

Even tho' I have double-density drives, I just tried booting from a single density system disk. The original Osborne system disk.

System loaded cp/m and help perfectly. I hit ESC to leave the help system and got the A> prompt. I then did a dir of the single density disk in B. Again, read perfectly.

I repeated the whole process above, with no problems.

It's beginning to seem that my system has trouble with booting and/or reading double-density disks.

Yep - just powered off and did the whole thing again. No problems with booting and reading SD disks. Even tho' I've got the 1.4 ROM (which supports DD), DD drives, and the optional DD card installed.

Any thoughts? Should I just be happy with the SD system as is? (even tho' all my disks but four are DD ...)

Progress!
T.

tezza
August 14th, 2009, 12:18 PM
OK - one step at a time.

Even tho' I have double-density drives, I just tried booting from a single density system disk. The original Osborne system disk.

System loaded cp/m and help perfectly. I hit ESC to leave the help system and got the A> prompt. I then did a dir of the single density disk in B. Again, read perfectly.

I repeated the whole process above, with no problems.

It's beginning to seem that my system has trouble with booting and/or reading double-density disks.

Yep - just powered off and did the whole thing again. No problems with booting and reading SD disks. Even tho' I've got the 1.4 ROM (which supports DD), DD drives, and the optional DD card installed.

Any thoughts? Should I just be happy with the SD system as is? (even tho' all my disks but four are DD ...)

Progress!
T.

Tom, are you sure the DD system disks you have are not now corrupted from all the random disk activity during a crash?

Tez

NutmegCT
August 14th, 2009, 12:47 PM
"Tom, are you sure the DD system disks you have are not now corrupted from all the random disk activity during a crash?"

Hi Tez. Recently I haven't been too sure of anything! Per the OCC user guide, if I boot using a SD system disk, the system thinks it's a SD system and can only read/write SD disks. If I boot using a DD system disk, the system should read/write SD and DD disks.

Just so I don't jump to conclusions ... how could I check to see if a disk is DD or SD? I took what I think is a DD system disk, one of the ones I can't boot from, and can't successfully read it after booting using a SD system disk. But honestly, I don't know how to tell a SD from a DD disk just by looking at them. They all seem to have the upper and lower "read/write" windows, and the write protect notch.

I just this minute tried booting from an original Osborne DD system disk; the label says "double density". BOOT ERROR. I then booted from an original Osborne SD system disk. Booted fine, but won't read that same DD system disk in the other drive. BDos error.

Edit: it would be very helpful if I could find the actual instructions for adding the DD board. I've got the proper 1.4 ROM, the DD board, the DD [Edit: DD board] to main board cable, and the DD drives [Edit: and cable set] from my old computer. But I wonder if there's some jumper that needed changing. The DD Drive Manual only tells how to use the DD system - not how to install it.

dave_m
August 14th, 2009, 01:22 PM
Tom, are you sure the DD system disks you have are not now corrupted from all the random disk activity during a crash?

Tez

Tez,
I wish that you could send Tom a fresh Osborne DD system diskette, but from your neck of the woods, it would take weeks. :(
-Dave

NutmegCT
August 14th, 2009, 01:32 PM
GENTLEMEN!

Reading Dave's last post I got to thinking. I went upstairs and rummaged around, and found one of my old original Osborne DD system disks. [Edit: I haven't used that disk for over 20 years.] It actually says DD on the label. Brought it down, slipped it in the A drive - and it booted!

However, system won't boot from that same DD disk if booted from the B drive. BDos error.

Interestingly, if I boot from the DD system disk in A, I *can* read a DD disk in B. Just did an xdir on another DD disk and see it holding 185K - so it is obviously a DD disk.

Looks like the DD drives are working - on *most* of the disks, but not able to boot DD system from the B drive.

T.

dave_m
August 14th, 2009, 01:38 PM
Tom,
Did the flashing screen and squeals suddenly go away? Is your system still all buttoned up? If so, it is possible for things like that to return, but so far so good.

If it returns, it may be better to leave power off until you plan a next step as recycling power under those conditons is hard on a power supply.

Lorne
August 14th, 2009, 01:45 PM
Edit: it would be very helpful if I could find the actual instructions for adding the DD board. I've got the proper 1.4 ROM, the DD board, the DD [Edit: DD board] to main board cable, and the DD drives [Edit: and cable set] from my old computer. But I wonder if there's some jumper that needed changing. The DD Drive Manual only tells how to use the DD system - not how to install it.

I've been watching this one just for fun, and was starting to wonder about the DD upgrade.

I have the manual:
"The Double Density Upgrade for the Osborne One Computer - Installation & Operating Instructions" (has photos too!). It was from Nuevo Electronics Corporation, Richmind, TX.
I also have a manual for "The OZROM 1E - A Replacement ROM for the Osborne 1 Computer" from Micro management, Inc.

I'm running out for a haircut, but will scan the docs when I get back.
PM me your email address, and I'll email them to you later.

tezza
August 14th, 2009, 01:46 PM
GENTLEMEN!

Reading Dave's last post I got to thinking. I went upstairs and rummaged around, and found one of my old original Osborne DD system disks. [Edit: I haven't used that disk for over 20 years.] It actually says DD on the label. Brought it down, slipped it in the A drive - and it booted!

However, system won't boot from that same DD disk if booted from the B drive. BDos error.

Interestingly, if I boot from the DD system disk in A, I *can* read a DD disk in B. Just did an xdir on another DD disk and see it holding 185K - so it is obviously a DD disk.

Looks like the DD drives are working - on *most* of the disks, but not able to boot DD system from the B drive.

T.

Tom,

It could be that that original DD disk is corrupted then. If you only have ONE DD boot disk left I'd be very careful. With a non-working B drive, I guess you can't make a copy? Are you able to use a Dave Dunfield disk image and make one on a PC? As I said, in my repair jobs with the Obsorne where the system would crash and burn, the crashing would sometimes corrupt whatever disk was in the boot drive.

As to the B drive problem, I had a similar thing with my Kaypro (you can read about it here (http://www.classic-computers.org.nz/blog/2009-01-18-kaypro-drive-repair.htm)). Could be dirty heads, incorrect speed, mis-aligniment or some problem with the disk clamp.

Tez

NutmegCT
August 14th, 2009, 01:50 PM
Dave - yes, all those weirdnesses have disappeared. I'd been running it power on for over an hour. Never had a single problem with any SD disks; even booted with the newly found DD system disk.

However, while in DD mode, I changed B disks and did a CTRL-C to notify the system that the disk was changed. As per usual, the A drive spun, but could not read the A disk (the DD disk I booted from).

Then I tried a reset, and it *still* couldn't boot from that DD system disk. It does however still work fine booting from either A or B with a SD system disk.

Lorne - thanks very much for the offer. I'll PM you my email.

Tom

NutmegCT
August 14th, 2009, 01:58 PM
Tez - just read your post. That DD system disk is write protected (sticker cover the write notch). I'd *think* that would mean it couldn't get corrupted, eh?

You may be on to something with the head cleaning. I certainly haven't cleaned the heads in over 20 years either (of course, they haven't been used much in the last 20 years ...).

Edit: I'd *think* that a dirty head would have more problems with a DD disk (narrower tracks?) than a SD disk, right?

As I don't have a cleaning disk, how should I clean the heads?

Tom

dave_m
August 14th, 2009, 02:15 PM
It could be that that original DD disk is corrupted then. If you only have ONE DD boot disk left I'd be very careful. With a non-working B drive, I guess you can't make a copy? Are you able to use a Dave Dunfield disk image and make one on a PC? As I said, in my repair jobs with the Obsorne where the system would crash and burn, the crashing would sometimes corrupt whatever disk was in the boot drive.



Tez, this is good advice. By the way I noticed that you are on-line right now. What time is it in New Zealand? It's 3:15 PM in So Cal.

dave_m
August 14th, 2009, 02:27 PM
Tez - just read your post. That DD system disk is write protected (sticker cover the write notch). I'd *think* that would mean it couldn't get corrupted, eh?



Tom,
No, I think all bets are off if the disk drive suffers a power transient while reading a track. It may even cause a true head crash where the read head touches the media damaging the floppy. Power loss at the wrong time can cause all kinds of bad things.

tezza
August 14th, 2009, 02:36 PM
Hi Dave,

Just got back on after getting some caps in town for my own problem being discussed on this form...that of the AT power suppy (which turned out to be the disk controller). Anyway, time right now is 10.32am Saturday.

Tom,

I found write-protecting the disks DID NOT stop them being corrupted from a Osborne melt-down. In most cases, where I had garbage screen, drives randomly turning on and off and beeping...the disk was trashed!

As you can imagine, until I realise this it caused hours of puzzelment.

Ok, I'm off to fire up the soldering gun to replace some caps in this disk controller!

Tez


Tez

NutmegCT
August 14th, 2009, 02:58 PM
Argh - doesn't sound good for the disks I've been using, that's for sure.

I do have a 300baud modem, if there's a way to download to disks. But if the DD part of the system is unreliable, and the disks can be trashed ... now I'm pretty reluctant to use the system at all!

Any suggestions on cleaning those drives?

Thanks.
Tom

dave_m
August 14th, 2009, 03:10 PM
Sorry, I don't know much about cleaning disk drives but be careful not to push the heads out of alignment.

tezza
August 14th, 2009, 03:52 PM
Argh - doesn't sound good for the disks I've been using, that's for sure.

I do have a 300baud modem, if there's a way to download to disks. But if the DD part of the system is unreliable, and the disks can be trashed ... now I'm pretty reluctant to use the system at all!

Any suggestions on cleaning those drives?

Thanks.
Tom

I don't think it's to do with the DD part of the system. I think you'd find if you had the SD disk in there and the computer spat the dummy, that disk would be in danger of being trashed too.

When I was working on my own Osborne issues and wanted to take measuments with the power on, I alway removed any disk from the drives just in case it through a random fit (which it did often, when I had that Drive B short problem).

As to cleaning the heads, I use a 5 1/4 disk cleaning kit. It's a kind of paper absorbant platter put into a normal disk sleeve. You put solution (isopropyl alcohol I think) onto the platter and spin it in the drive for a 30 seconds or so. You can get them on e-bay now and again.

You can also clean the heads directly with isopropyl alcohol. Be careful though, not to move the heads out of alignment if you do this.

Tez

NutmegCT
August 15th, 2009, 03:03 AM
Just a quick update. Got up this morning and powered up the Osborne using SD system disk. No problems, ran WordStar v2, changed data disks, etc.

Rebooted with DD system disk, immediately formated a disk for DD, then did DiskCopy to put the entire DD system/help/util onto the new disk as a backup. Format was cranky (DD), but finalized a DD disk with a few E sectors (error, locked out). Could boot as DD system using that new copy of the system disk. Switched to another disk in B, and got "bdos error bad sector" on the new B disk. Immediately removed both disks and powered off (fearing I could corrupt the disks in the drives).

Off to the weekend job. I feel much better that system seems stable in SD mode, and when I receive that manual from Lorne I can check the DD installation. Interesting that several online references talk about the DD upgrade needing ROM 1.43; mine is labeled 1.4 on the chip, but it's the chip that was in my original DD machine which worked fine with DD drives and disks.

Also interesting that my power harness doesn't match either of the two harnesses in the Tech Manual; Tech Manual shows both versions of that harness have two 4-pin sockets for DC feed from the PSU; the harness that I'm using successfully has only one socket for DC feed from the PSU. My original harness has two of those 4-pin sockets, but using that harness results in the system locking up at power-on.

To do when I get home tonight: carefully clean the drive heads with q-tip and alcohol. Maybe do more reading on the power harness situation - the socket that feeds DC to the logic board is a bit strange. Wires from PSU only lead to half the socket pins, and two of those pins are jumpered with a short piece of green wire. Strange - but that's the harness that works. Figuring out how to orient those un-notched sockets is problematic, as the tech manual always uses instructions like "with logic board face down and CRT facing technician, plug harness socket into board with red stripe to the left". Left of what - the board? or the technician? And the harness doesn't have a stripe; it's several separate wires, one of which is red. Fun! A color picture of someone's power harness connection to the logic board would be very helpful!

Have a good weekend everybody. And thanks again for following me through all this so far.
Tom

Lorne
August 15th, 2009, 09:13 AM
I scanned the two Double Density Upgrade documents.
One of them is too large to email (scanned in color so photos are readble but that results in a larger file).
I've put them on my FTP site, and emailed NutmegCT on how to access the FTP site.
If anyone else wants them, PM me your email address and I'll send you the instructions as well.
I'm only leaving them on the FTP site for a couple days.

dave_m
August 15th, 2009, 12:15 PM
Also interesting that my power harness doesn't match either of the two harnesses in the Tech Manual; Tech Manual shows both versions of that harness have two 4-pin sockets for DC feed from the PSU; the harness that I'm using successfully has only one socket for DC feed from the PSU. My original harness has two of those 4-pin sockets, but using that harness results in the system locking up at power-on.

I have been reviewing the Osborne field service manual. It seems you have a repaired or homebrew power harness. The reason it works with only one connector hooked up is that the two connectors are identical. The possible problem is that since only one is hooked up, you are routing DC power to the entire computer with one set of wires which can cause a small loss in the +5V and +12V voltages in the wires called IR drop. If the 5 volts drops under +4.75V at the system board, the computer may behave erratically. If the 12V drops below around +11.4V at the disk drives, the drive motors may run too slow.



the socket that feeds DC to the logic board is a bit strange. Wires from PSU only lead to half the socket pins, and two of those pins are jumpered with a short piece of green wire. Strange - but that's the harness that works.

This is the same problem as above. Only one set of power wires are hooked up, there should be two sets. On the logic module the manual states that pins 1 and 7 should be red wires and are both +12V. Pins 2 and 6 should have yellow wires and are +5V. Pins 3 and 5 have orange wires and are common (power return). Pin 4 is green and it says zero volts ( this may be chassis ground).



Figuring out how to orient those un-notched sockets is problematic, as the tech manual always uses instructions like "with logic board face down and CRT facing technician, plug harness socket into board with red stripe to the left". Left of what - the board? or the technician?

It means to the technician’s left.





And the harness doesn't have a stripe; it's several separate wires, one of which is red. Fun! A color picture of someone's power harness connection to the logic board would be very helpful!

Again this is an indication of a homemade harness.

The following is important! Remember when I asked you to keep a detailed log everything you do? When you remove a connector for the first time, always note how the cable goes on (pink wire on left, keyway to right, etc). It even helps to sketch a picture of it sometimes. A mistake in hooking up a cable can be disastrous. Hang in there you are a fast learner.

tezza
August 15th, 2009, 12:40 PM
The following is important! Remember when I asked you to keep a detailed log everything you do? When you remove a connector for the first time, always note how the cable goes on (pink wire on left, keyway to right, etc). It even helps to sketch a picture of it sometimes.

I couldn't agree more. Unless disassembly is very simple, I always take close up digital pics at each step. I've had to use them on occasions!

I've attached an image of my PSU, snipped from a larger picture of a dissected Ozzy. Hope this helps.

Tez

pavery
August 15th, 2009, 03:43 PM
Just a quick update. Got up this morning and powered up the Osborne using SD system disk. No problems, ran WordStar v2, changed data disks, etc.

Rebooted with DD system disk, immediately formated a disk for DD, then did DiskCopy to put the entire DD system/help/util onto the new disk as a backup. Format was cranky (DD), but finalized a DD disk with a few E sectors (error, locked out). Could boot as DD system using that new copy of the system disk. Switched to another disk in B, and got "bdos error bad sector" on the new B disk. Immediately removed both disks and powered off (fearing I could corrupt the disks in the drives).

Tom

IMHO if your system is working fine in SD, then the disk drives are fine, ie, no fault with those. This is because SD is inherently less reliable than DD & SD requires tighter tolerances from your drives.

Philip

NutmegCT
August 15th, 2009, 04:21 PM
Thanks again gentlemen.

Now that I've heard my power cable is probably non-standard - and probably supplying less power to the main board than is required - I need to find out why the *standard* cable I have causes the system to freeze up. Even when it's plugged into the main board exactly like the non-standard cable that works reliably (at least in SD).

I'm betting that either there's a broken wire, or I've been putting it in backwards, just following the orientation the non-standard plug was installed before the "melt-down".

Anyone have a picture of the power cable connection to the main board? The white plastic socket that's right next to the disk drive cable connection on the main board - showing the orientation of those color wires?

Note that on the OCC1, the disk drives are actually powered through the ribbon cable, not through a separate power cable. Maybe my setup has been sending insufficient power through that "non-standard" cable ... and my "standard" cable is either screwed up or installed backwards.

Thanks.
Tom

Lorne
August 15th, 2009, 07:00 PM
Here's some photos of my double density upgrade board.

One thing - I've read bits and pieces of this post as I'm interested in Osbornes. I may have forgotton some of what I saw, and I don't want to have to go back through the 10 pages, but does this machine boot (when it does boot), to the normal Osborne screen?
Mine boots to the following screen, and then after hitting Enter I get the normal screen. I would suspect with a double density ROM that you shouldn't be getting the regular Osborne screen at the start (just a thought).

1939

Here's the other photos of the board - are these what you were looking for?
If so, I've put them on my FTP site so you can grab higher res copies of them there.

1940

1941

1942

1943

dave_m
August 15th, 2009, 07:54 PM
Now that I've heard my power cable is probably non-standard - and probably supplying less power to the main board than is required - I need to find out why the *standard* cable I have causes the system to freeze up.

Not a bad idea to fix that harness. It might help to have a person helping. With the harness removed, one holds a probe on the power supply end while you probe the system board end. Flex the harness during the test to check for intermittent continuity. After that, you are not done. You need to check for shorts. While one person holds the probe on the power supply end, say the +5V line, you check for dead opens on the other lines (proper). If you get any signs of continuity, you may have a short. Check the AC/chassis ground lines too if you have a wire list or schematic for those lines.



Anyone have a picture of the power cable connection to the main board? The white plastic socket that's right next to the disk drive cable connection on the main board - showing the orientation of those color wires?

This may not be a problem if it is not keyed. The system board power connector seems to be a 7 pin connector that is wired symmetrically. From the manual, the end pins 1 & 7 are both red wires that have the +12V. Pins 2 & 6 should be yellow wires that carry the +5V. Pin 3 & 5 are orange and have the common return lines. Pin 4 is chassis ground. So it seems to me that it will work plugged in either way. Do you agree? Verify before you plug it in or if yours is not to this color code.



Maybe my setup has been sending insufficient power through that "non-standard" cable ...

It may be OK. The best way to check is to measure the 5V somewhere on the system board. If it reads above +4.75V, it is probably OK. The 12V at the drives should read above 11.4V. But I don’t know how hard it would be to check these voltages with everything buttoned up.

If everything works OK when you clean the disk heads, it may be best just to leave good enough alone. Fix the spare harness for use when the Osborne next fails.

NutmegCT
August 16th, 2009, 02:35 AM
Lorne - thanks for the pictures. You've got a non-Osborne ROM (OzRom); I've got the standard Osborne 1.4 ROM, which supports DD but doesn't have the bells and whistles yours has. And that picture confirms what Dave and others have said; the power cable wires are symmetrical, so reversing isn't likely to be a problem.

I've attached a picture of my own non-standard power socket, taken from the back of the board. Note the wires are red, yellow, orange, and green - and the green is jumpered into the next two holes. Now that's weird, as the center pin on the board is literally not connected to anything.

And yet, that non-standard cable is the one which works on my board; the standard cable (red, yellow, orange, blank, orange, yellow, red) results in the system being totally dead when powered up.

By the way, take a look at the second picture. The green wire on that non-standard plug runs *inside the harness* directly to the main power cord board (the red switch board); it's actually on a spade connector, connecting to a stud wired to the green/yellow wire coming off the incoming mains power. Now *that* seems totally bogus.

Edit: keep in mind that I'm working on my Osborne I, not a Ia. Serial number is A14649

Anyway, off to Sturbridge. Two new calves born Friday and Saturday.

T.

Lorne
August 16th, 2009, 06:21 AM
Edit: keep in mind that I'm working on my Osborne I, not a Ia. Serial number is A14649

T.

Ahhh, wrong assumption on my part re: the 1a.

I have a 1 as well (single density though), so if you need some photos from that, let me know.

dave_m
August 16th, 2009, 10:13 AM
I've attached a picture of my own non-standard power socket, taken from the back of the board. Note the wires are red, yellow, orange, and green - and the green is jumpered into the next two holes. Now that's weird, as the center pin on the board is literally not connected to anything.

By the way, take a look at the second picture. The green wire on that non-standard plug runs *inside the harness* directly to the main power cord board (the red switch board); it's actually on a spade connector, connecting to a stud wired to the green/yellow wire coming off the incoming mains power. Now *that* seems totally bogus.


Tom, it seems that a previous owner had to make some "workarounds" to fix some problem in the system. It appears to me that earth ground (Edison ground) has been routed directly to the DC common returns at the system board cable (pins 3 & 5). Perhaps this is an indication of a problem on pin 4 on the system board.

Usually for optimum system performance (lowest noise), a single point grounding scheme is employed to connect Edison ground to the chassis near the Osborne AC panel only.

Before you plug in the fixed power harness, you will now have to do some testing to see if there are lurking issues like shorts to pin 4 from who knows where. Old computers can be a series of complications.

So keep good notes on all this so you know where to start with a repair, but if the Osborne is working now to your satisfaction, I would follow the advise a Russian General Officer during the cold war whose motto was, "Better is the enemy of good enough".
-Dave

Darshevo
August 16th, 2009, 12:35 PM
I threw together a quick website today to gather some of the excellent pictures and technical information that has been brought together in this thread. Thank you to everyone who has contributed. I put footnotes on the pics as to who provided them, I will do the same on request for the various PDF files

It can be viewed at.

http://retrocomputing.myauctionplace.com/osborne

-Lance

tezza
August 16th, 2009, 01:14 PM
Nice page Lance,

Like people, these osbornes seem to get cranky with age, and it will be good to have a central website with a lot of this info on it.

Tez

NutmegCT
August 16th, 2009, 03:18 PM
Dave: "Before you plug in the fixed power harness, you will now have to do some testing to see if there are lurking issues like shorts to pin 4 from who knows where. Old computers can be a series of complications."

Interesting that pin 4 on the board is a "dummy" pin - not connected to anything (except that strange harness plug I have). On the underside of the board, I see the circuit completely ignores that pin; etched lines go to the 3 pins on either side, but not to pin 4 - which appears as a "rivet head" on the underside of the board.

Lance - congrats on your new Osborne site. I never expected this thread to go on so long, but have to admit the information shared by forum members is certainly priceless.

Tez - I certainly hear you on "cranky with age". And that certainly applies to me as well as to my Osborne.

Lorne - yes, it might help if you could email or post a picture of the power harness connection to your Model 1 system board. Unless it looks exactly like the one you've already posted from your Model 1a.

As there were many "system improvements" from the very first version of the Osborne 1, who could ever tell why my system has that strange harness modification. Yet that's the harness that powered the computer when I first bought it several weeks ago, when it seemed to be working fine. Then I got it home and found the ram chip problem.

Cranky is perhaps a kind term for part of the aging process!
Tom

NutmegCT
August 18th, 2009, 12:50 PM
Thought I should bring this thread to a close with some positives vibes.

For the last two days I've been running in both DD and SD modes. Learned in passing:

- booting in DD mode allow reading of both DD and SD disks; but after about an hour of use, the reading of DD disks becomes unreliable (lots of "bdos err on x: bad sector" messages).

- repeating the process on the same disks *after an hour's cool-down* gives no errors at all.

- as of today at 4pm EST I've been able to read nearly every single SD and DD disk I've got, with no error (long as the system remains relatively cool).

- one of the biggest highs I've felt in many years was this morning when I booted from a backup copy of the original Osborne DD System 2.2, started WordStar 2.26, and opened up all the chapters of my dissertation. I hadn't seen those files opened for over 25 years.

- I still have lots to learn/remember!

- without knowing the in's and out's of solving the "heat" problem, I'm pretty satisfied with how my OC1 is running. Not perfect, but at its age, pretty darn good. Tho' I'm still not sure about when I need to use CTRL-C at a disk change.

- if anyone knows where I can download/purchase the old FOG library disks, please let me know.

Here's a picture from about 20 minutes ago. Been running perfectly for nearly an hour. I've even got the original sales invoice, documentation, and sales literature. I'm a happy camper right about now.

And none of this would have been possible without this forum, and all your help. Thanks all.

Tom
OCC1, SN A14649

Mike Chambers
August 18th, 2009, 01:48 PM
i'm not going to read all 11 pages right now, but has it been suggested (probably) to physically swap drive A and B?

EDIT: seems you got it working, excellent. another useless post from me woohoo.

dave_m
August 18th, 2009, 02:17 PM
booting in DD mode allow reading of both DD and SD disks; but after about an hour of use, the reading of DD disks becomes unreliable (lots of "bdos err on x: bad sector" messages).


I noticed your model does not seem to have an internal fan. As an experiment, try placing a fan by the disk drives and see if that helps.



And none of this would have been possible without this forum, and all your help. Thanks all.


It was fun.
-Dave

Lorne
August 18th, 2009, 03:01 PM
- if anyone knows where I can download/purchase the old FOG library disks, please let me know.


I've got some old FOG newsletters (not yet scanned), and all of the 17 Osborne Portable Companion Magazines (some scanned, some not yet).

If you want the Portable Companion scans, email me, and I'll put them on the FTP site for you to download (they're big as they're in color).

Same for you Tez, the other one who wanted the DD upgrade docs, and anyone else for that matter.

tezza
August 18th, 2009, 04:17 PM
Same for you Tez, the other one who wanted the DD upgrade docs, and anyone else for that matter.

Sure thing, great!

Tom, on my Osborne 1a there is a flap at the back on the case on the top which you pull open when the machine is on. It uncovers venting slots presumably to cool the machine.

Does the Osborne 1 have this feature?

Tez

NutmegCT
August 18th, 2009, 04:32 PM
Hi Tez - the Osborne I was pretty basic. Top of the case is vent-less; one of the brochures describes the Osborne as "no fan needed - cooled by convection." The addition of that vent on the Ia must have greatly increased the convection airflow.

The Ia had a sliding vent lid, stronger case, a better logic board mount, and a more robust latch system for the keyboard. Also had a toggle switch for input voltage (115/230), and an additional fuse where the power cord enters the case.

Edit: take a look at this - a guy did a photo-shoot of dis-assembling an Osborne I. He's got the same non-standard power harness socket that I've got (the green jumper connecting 3 pins). Guess mine isn't as weird as I thought!

http://i.techrepublic.com.com/gallery/193080-500-310.jpg

http://content.techrepublic.com.com/2346-13636_11-193055-25.html

You can see one of the prototype Osborne I models at:

http://www.youtube.com/watch?v=LzLxfN7vXhI

Tom

Lorne
August 18th, 2009, 05:07 PM
The addition of that vent on the Ia must have greatly increased the convection airflow.

Tom

And that didn't quite do it either, because then there was the OsCool fan which mounted on top of the vetilation grille. It does quietly move some more air, but only if you remember to put it on. Seems the rest of them figured out afterward, that an actual built-in fan was the ticket.

tezza
August 18th, 2009, 05:11 PM
Yea, I couldn't see any sign of the cooling flap in the photo, which was why I asked.

Re: the comments in the "cracking open" link you posted. It looks like those pics triggered nostalgic memories for lots of people going by the comments :)

The osborne 1 was WAY beyond my financial resources when they first came out, but I remember really wanting one. The fact you could carry your computer with you in one easy package had a lot of appeal!

The design was pretty nifty for the time really. It was those huge full height 5.25 inch drives that proved a major constraint. In the end it was Kaypro, who figured out the best way to deal with this issue (i.e. stacking them together) leaving more room for a larger screen.

I do love seeing the innovations (some successful, some less so) embodied in these old machines.

Tez