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ryaninspiron
December 5th, 2016, 01:34 PM
Hello all,
I am the proud new owner of two IMSAI 8080s and I have several questions about what to do next. I have had a Cromemco system 2 before this but was never able to get it running possibly due to high levels of oxidization and broken/non functioning tantalum caps that need replacing. I have a bunch of Cromemco boards and some others like a Tarbel Cassette card but never was able to really test any of them.
Anyway I the two machines are loaded with ram boards and a few other peripherals.
8080 #1 has the a MPU-A Rev 4, 3x Industrial Micro Systems 8k Memory BD, a '76 North Star MCD-A2, a '76 IMSAI SIO rev-3, and a '78 Compupro Godbout Active terminator no.106
8080 #2 has An MPU-A Rev 4, 2x '77 ithica audio 8k static ram boards, a '76 IMSAI RAM-4A, A Cromemco ZPU, A Dynabyte Naked Terminal Card, A '77 Tinker Toys Disk Jockey rev B, A Processor Technology VDM-1(without the ribbon?), and finally a '77 Cromemco 8K Bytesaver 2 with two mystery PROMs labeled MFILL 1.0

34595

So about those new IMSAIs
1. what to I do about reforming the capacitors? Should I worry about doing it? One of them was powered on for the ebay listing pictures and the other one has a mysterious twist lock type of connector that I am clearly going to have to put a cord onto. Do I need to go out an find a variac or use incandescent bulbs in series before I can test these machines? I have read about the switching psu upgrades but I may want to leave one machine all original and the other as a "daily driver" lol. Thoughts?34599

2. 8080 #1 has 3 missing switch caps, 8080 #2 has some unfamiliar yellow,orange,white, and black caps + is missing the front panel switch escutcheons. Should I head over to imsai.net and order replacements for all these things?

3. One has 10 sockets installed and the other has 14, was this just the preference of the person who built it?

4. Can I use the Tarbell card to get software transferred to them from my laptop?

5. Any ideas what could be on the two PROMs labeled MFILL 1.0 34597

6. I also have an ASR 33, I would love to hook that up to this some day. IMSAI SIO Card maybe?

7. The Dynabyte naked terminal seems to take a parallel keyboard which I don't have, am I better off building a ps2 converter for this?

8. What drives did this Tinker Toys Disk Jokey work with? I can't find any documentation about it and it seems its from Gorge Morrow's earlier days.34598

9. I have no software for this system, where do I start?

10. Any top recommended new s100 boards to add(IDE Card Maybe)?

Sorry for the flood of questions but I want to learn as much as I can about these two machines. Any contribution is greatly appreciated. I have always wanted an IMSAI 8080 and am very excited to get started.

Regards,
-Ryan

new_castle_j
December 5th, 2016, 06:48 PM
Hello Ryan!

It's great to have you here and to see your enthusiasm. You've posted a lot of good questions, but I think more generically, you're asking "where do I start?" I'm going to reply the best I can anecdotally.

My IMSAI came out of 25 years being stored in a cold dirty attic, it had mouse droppings inside and was absolutely filthy. I did not have a variac, so after a good cleaning, and with all the boards removed and I powered it up. I let it idle for quite a while under supervision and checked the voltages on the buss, everything seemed fine. I don't know how risky I was being without using a variac.

Then I added the processor board, and powered up, one of the tantalum capacitors on the processor board blew immediately. I replaced the cap and tried again, everything seemed fine. After that I added a memory board and powered up, no explosions or magic smoke was released. With just the memory and processor board in the buss, I started depositing values into memory via the front panel and reading them back. At this point I was getting totally different things back than I was depositing into memory, and the LED's would flicker or light dimly, turns out my front panel board was out of whack. I replaced all the caps on the front panel board, now the LED's were lighting up bright, but I still wasn't getting the values back out of memory that I was depositing in. I swapped in a different memory board -- a static memory board this time, and viola, memory was getting written and read back properly.

Time to run my first program, I toggled in the "kill the bit" program, and executed, but got nothing. Tried again, but got nothing still. Then I single stepped thru the program and checked that everything was entered correctly, I found and error and corrected it, then executed... and it worked! I had proven that my system was working at a very basic level.

In between all of the steps that I am summarizing, there was a lot of reading of manuals and other resources, taking a bunch of guesses and trying to devise tests to prove or disprove my guesses in order to figure out what was going on. It all didn't happen in an afternoon either, but I was persistent and I had to take some breaks in order to re-form my enthusiasm as well.

My best advice is to start in a similar fashion, just the basics. Figure out if you can get a processor and some memory to respond to the front panel, and try toggling in and running a program, or adding some numbers together. I think most of this is covered in the IMSAI manual. Be systematic and build up the system in steps like this.


>Should I head over to imsai.net and order replacements for all these things?
I wouldn't, I think you have enough hardware between the two machines to come out with 1 complete one

>One has 10 sockets installed and the other has 14, was this just the preference of the person who built it?
Could be, the IMSAI mainboards came in an 11 or 22 socket configuration from the factory (the front panel board sits in a socket too) I'm guessing the one you say that has 10 sockets is really 11 if you include the front panel. The one with 14 sockets could either be a non-IMSAI brand mainboard or custom assembled to leave out some slots.

>Can I use the Tarbell card to get software transferred to them from my laptop?
I have not personally heard of doing this, but wouln't rule it out. I think the Altair computer group on yahoo archives tape based software, not sure how it gets loaded back into a system though

>Any ideas what could be on the two PROMs labeled MFILL 1.0
No idea, could be something the previous owner put together, or could just be a bunch of 00s, MFILL kind of sounds like it's just filling up memory space as a placeholder.

> I also have an ASR 33, I would love to hook that up to this some day. IMSAI SIO Card maybe?
I think that the IMSAI SIO is compatible with a teletype, the manual for the SIO card will be able to confirm

>The Dynabyte naked terminal seems to take a parallel keyboard which I don't have, am I better off building a ps2 converter for this?
I don't have any experience with the naked terminal board, however I would start with serial I/O to a dumb terminal before attempting to use this board.

>What drives did this Tinker Toys Disk Jokey work with? I can't find any documentation about it
http://maben.homeip.net/static/S100/morrow/cards/Morrow%20Disk%20Jockey%201%20Controller%201978.pdf

>I have no software for this system, where do I start?
There's various archives around the internet, Don Maslin's archvie is good place to start: http://www.retroarchive.org/maslin/index.html

>Any top recommended new s100 boards to add(IDE Card Maybe)?
I don't think you'll be able to answer this question for yourself until to get a little further into the experience.

MicrocomputerSolutions
December 6th, 2016, 03:00 AM
Do you intend on running both of the Imsai? If so, replacement parts for the missing or damaged parts sooner or later. It may take a while to contant Imsai, and actually get parts. You need to plan ahead.

The switch eschutcheon costs about $72. You can can the switch paddles separately for about $7.50 each. You can move the switch paddles from the incomplete to the almost complete Imsai, and move the parts around to get one complete Imsai.

Photos of the insides of both Imsais would be helpful. The one with the funny power cord connector might have a "Universal Power Supply" (later power supply which can be configured for different input voltages) where as an earlier Imsai with a standard power cord will probably have a 110vac only power supply.

glitch
December 6th, 2016, 05:22 AM
Nice systems! You don't have to worry about upgrading the power supplies to switchers to make it more usable, if the originals work they'll do fine. If your chassis is lightly loaded, the +8 rail will be more like +10 and the regulators will run hot, so that's often a reason for switching to a switchmode supply -- often a 7V Mean-Well supply, since most 5V regulators will work fine at 7V.

If you have an old analog multimeter (Simpson 260, et c.) you can get a feel for whether the caps in the power supply are any good by removing them and putting the meter across them in a low ohms range. This will charge the cap from the Wheatstone bridge's supply and, if the cap is any good, you should see the resistance head down to near zero. Disconnect a lead, flip it over to the 10V scale, and reconnect. You should see the voltage slowly drop to zero. This is a quick test to make sure the capacitors aren't shorted or totally dried out. Replace the ones that fail the test, put the others back in and hit the power switch. If you want to run it through a "dim bulb" tester before going to full line voltage, it certainly won't do any harm.

You can also reform the capacitors with a bench supply or old AT/ATX computer supply, or even a number of batteries. Just put a current limiting resistor in series with the capacitor, it'll build up to near the supply voltage.

The hardest thing to troubleshoot will probably be the front panel. I end up repairing them for people more often than other cards. Since you have some PROM cards, you can burn test ROMs and not depend on the front panel deposit being functional.

As mentioned above, be careful when putting power to old tantalum capacitors. Personally, I bring up unknown boards with my bench supply, which has a built in adjustable current limiter. So far that has kept boards brought up that way from exploding tantalums, even when I've had shorted ones. If you don't have the means to do that, I would put a board in the middle of the chassis and put something in front of it (heavy plastic plate, sheet of FR4 fiberglass, et c.). Sometimes those capacitors *really* let go -- you can get a bang with flying debris, or a jet of flame that will make a scorch spot on the back of the board in front of it. Whatever you do, make sure you're not looking into the chassis when you hit the power switch!

ryaninspiron
December 6th, 2016, 11:26 AM
Wow thanks for the great feedback guys, I had a very exciting morning but its all good news so far. I think I will refer to the two machines as #1 and #2 for now.
IMSAI #1 has a regular cord and is only missing three switch caps I moved them over from #2. I may just keep #1 all original parts and #2 will get the replacement parts. I have tested #1 and got it up and running with test program 1 and 2, They ran perfectly and was a huge relief to see it working.
The only issue I can find with the front panel is that switch 0 has issues turning off unless I push it down harder than the others and it seems about 2 or 3 other switches have intermittent issues turning off.
There with all this feedback I will just respond to it all in sections below.


new_castle_j,
>My best advice is to start in a similar fashion, just the basics.
I did just that and was able to run the two test programs so far. Nothing but the MPU and 8k Static ram installed at the moment.

>>Should I head over to imsai.net and order replacements for all these things?
>I wouldn't, I think you have enough hardware between the two machines to come out with 1 complete one
I may want to sell one at some point but I want to collect opinions on the matter. For all I know people here may have had bad results with them, just looking for feedback, Thanks.

>>One has 10 sockets installed and the other has 14, was this just the preference of the person who built it?
>Could be, the IMSAI mainboards came in an 11 or 22 socket configuration from the factory (the front panel board sits in a socket too) I'm guessing the one you say that has 10 sockets is really 11 if you include the front panel.
Well it seems they are both labeled as 22 socket on the solder masking. I am wondering if it was common to see them with missing connectors like this.

>>Can I use the Tarbell card to get software transferred to them from my laptop?
>I have not personally heard of doing this, but wouldn't rule it out. I think the Altair computer group on yahoo archives tape based software, not sure how it gets loaded back into a system though
As I was writing it I was trying to think of how I will get data onto this machine without drives but I am forgetting about the serial ports I guess. Idk, I brought it up because I've seen it done on an Apple 2e on YouTube but now that I think about it, This is probably just a far fetched idea that is not even possible. It would need many conditions to all line up just right.

>>Any ideas what could be on the two EPROMs labeled MFILL 1.0
>No idea, could be something the previous owner put together, or could just be a bunch of 00s, MFILL kind of sounds like it's just filling up memory space as a placeholder.
That's a possibility I guess, I didn't even think about memory filling, but why two EPROMs for just that?

>> I also have an ASR 33, I would love to hook that up to this some day. IMSAI SIO Card maybe?
>I think that the IMSAI SIO is compatible with a teletype, the manual for the SIO card will be able to confirm
Wow it turns out it does have a current loop hookup. Just need to fix my teletype selector card now but that's a whole other issue.

>>The Dynabyte naked terminal seems to take a parallel keyboard which I don't have, am I better off building a ps2 converter for this?
>I don't have any experience with the naked terminal board, however I would start with serial I/O to a dumb terminal before attempting to use this board.
Hopefully someone on here has one of these and can let me know, but I also don't have a dumb video terminal yet I was hoping this board could be the core of my terminal setup. Logically it should be a simple conversion and I can already imagine one that could be made with 7400 series chips. But I wonder what other owners of this board use.

>>What drives did this Tinker Toys Disk Jokey work with? I can't find any documentation about it
>http://maben.homeip.net/static/S100/morrow/cards/Morrow%20Disk%20Jockey%201%20Controller%201978.pdf
That link has been a GREAT help, with it I even learned that the board also contains a 232 and TTY current loop serial interface! Very cool. Great resource too.

>>I have no software for this system, where do I start?
>There's various archives around the internet, Don Maslin's archvie is good place to start: http://www.retroarchive.org/maslin/index.html
I have a feeling the hardest part will be just finding the stuff for this machine, Thanks for the tip tough.

>>Any top recommended new s100 boards to add(IDE Card Maybe)?
>I don't think you'll be able to answer this question for yourself until to get a little further into the experience.
I have to ask because for all I know there may be some s100computers board that I just have to add that will make life easier or something. I'd never know without asking. If anyone has a favorite board, let me know.

MicrocomputerSolutions,
>Do you intend on running both of the Imsai?
Either I'm running both at one point or I am selling one at some point. I definitely do want to make them both complete with original colored switches I'd say.

>You can move the switch paddles from the incomplete to the almost complete Imsai, and move the parts around to get one complete Imsai.
Good tip, I've moved the three red caps to the one with the regular cord (#1)

>Photos of the insides of both Imsais would be helpful. The one with the funny power cord connector might have a "Universal Power Supply".
I will post a series of close ups late tonight when I get home. I would greatly appreciate any help identifying these two power supplies. They look identical to me, but I don't know what to look out for.

glitch,
>You don't have to worry about upgrading the power supplies to switchers to make it more usable, if the originals work they'll do fine.
Glad to know, thanks.

Besides the test you've outlined, how do I know if the caps are working well enough? I have a scope, I'd assume I need to look for a smooth line on the buses correct?

>The hardest thing to troubleshoot will probably be the front panel.
Thankfully at least on #1 with the exception of a few iffy switches my front panel is in great shape.


>"As mentioned above, be careful when putting power to old tantalum capacitors. Personally, I bring up unknown boards with my bench supply, which has a built in adjustable current limiter. So far that has kept boards brought up that way from exploding tantalums, even when I've had shorted ones."
^
Wow I wouldn't have guessed to test them out of the machine like that. I do have an extra s100 backplane I bought a few years ago that I can hook up to my current limiting supply. I also have a simple riser card but I like that external test idea much better.
I have several questions about this process as I have almost thirty untested boards and I want to be careful about this.
How do I bring up the boards as I test them?
Set the voltage and bring up the current or limit the current low while bringing the voltage up?
Is there any signs I should watch out for? (besides explosions that is)
How long at full voltage until I can safely put a board in the system.
Once I test a board can I be pretty certain that it wont blow op in my system a week later? I believe I heard somewhere (maybe at VCF) That the biggest risk for explosion passes once they have been cycled a few times at voltage.(or am I just making this up?) after that warning I'm a bit nervous is all.

Thanks for all this GREAT feedback. I am already feeling much better prepared to have a great time with these systems.

Here are some pics of IMSAI #1 running after the power tests checked out. the previous owner put masking tape on the right side inside the cover to make the fan draw all its air from over the cards, only issue is they let it show from the front lip, I will have to clean it up a bit.

System waiting at 0000: 34610

Test program 2 running: 346113461234613

glitch
December 6th, 2016, 11:56 AM
Well it seems they are both labeled as 22 socket on the solder masking. I am wondering if it was common to see them with missing connectors like this.

Pretty common on kit-built machines. I have several MITS 18-slot backplanes that are built up with missing sockets here and there. A lot of people left a space between boards for better cooling (especially with the top off) so having every socket populated might've seemed like a waste of money.


As I was writing it I was trying to think of how I will get data onto this machine without drives but I am forgetting about the serial ports I guess. Idk, I brought it up because I've seen it done on an Apple 2e on YouTube but now that I think about it, This is probably just a far fetched idea that is not even possible. It would need many conditions to all line up just right.

Right, it's tricky to get dialed in with Apple IIs as well! Serial is easy though, and if you need it someone here should be able to burn a ROM with a useful serial monitor for you -- I probably can if no one else can.


Besides the test you've outlined, how do I know if the caps are working well enough? I have a scope, I'd assume I need to look for a smooth line on the buses correct?

Yeah, load it down with your intended board set and measure ripple on the various rails. Helps to have the 'scope in AC coupling since you'll be looking at, minimum, a 7V offset!



How do I bring up the boards as I test them?
Set the voltage and bring up the current or limit the current low while bringing the voltage up?

That's what I do. You can kind of get an idea about what the board should draw by the number and size of heatsinks on it.


Is there any signs I should watch out for? (besides explosions that is)

Once I start drawing around an Amp on +8, I wait a bit and feel the capacitors to see if anything is hot. Proceed slowly.


How long at full voltage until I can safely put a board in the system.

It's my understanding that tantalums usually fail from tantalum crystal shorts or absorbed humidity. Bringing them up slowly to full voltage should, at least in theory, warm the device up if it's got some lowish DC resistance, and burn out any tantalum crystals that might've grown. Some tantalum caps are "self-healing," which means they're designed so that when a shorting crystal is blown out, the result is an insulating oxide where the short was. I usually leave them running on the current limited supply for 5-10 minutes, just to make sure the current doesn't jump up.


Once I test a board can I be pretty certain that it wont blow op in my system a week later? I believe I heard somewhere (maybe at VCF) That the biggest risk for explosion passes once they have been cycled a few times at voltage.(or am I just making this up?) after that warning I'm a bit nervous is all.

I think I've only had one board that had a capacitor explode soon after slow bring-up on the bench supply. There's no guarantee with old hardware, who knows what it's been through over the past decades.

I've had a disproportionate number of tantalum failures with North Star S-100 boards, even compared to a big batch of MITS boards that were literally stored in a barn, so nowadays I just replace every tantalum on any North Star boards I work on. I don't know who North Star bought from, but apparently their capacitors don't stand the test of time well!

Dawsoca
December 6th, 2016, 02:02 PM
Ryan, for what it's worth, I use the John Monahan IBM PC Keyboard to ASCII Converter board to connect to my Dynabyte Naked Terminal. I think these boards are hard to come by because the later Propeller Console IO board works so much better. You might check the retrobrewcomputers.org PCB Inventory to see if any of these boards show up. The manual for the Naked Terminal is also on John Monahan's site and it shows the parallel connections.

34617
34616

> Charles

MicrocomputerSolutions
December 6th, 2016, 09:52 PM
The reason that you may have to push down on some of the switches is because of the design of the switches. The mounting bracket for the switch paddles that is prt of the switch is poorly attached to the switch body. Even normal use can cause the paddle mounting bracket to break loose from the main switch body. You may be able to resecure the paddle mounting bracket to the switch body with an adhesive like an epoxy, or maybe careful soldering, but I think most people replace the switches that develop this problem.

When considering additional boards, you need to keep in mind that early S-100 boards and systems do not conform to the IEEE-696 S-100 spec. and may not be compatible with modern S-100 boards without modification to the older boards and system or the newer boards. The Front Panel will only operate correctly with clock speeds of 2 or 3mhz. Most processor boards generate signals that will conflict with those generated by the Front Panel. Unless an aftermarket processor board has a Imsai Front Panel connector and optional jumpers and/or switches, it will not work with an Imsai Front Panel.


Wow thanks for the great feedback guys, I had a very exciting morning but its all good news so far. I think I will refer to the two machines as #1 and #2 for now.
IMSAI #1 has a regular cord and is only missing three switch caps I moved them over from #2. I may just keep #1 all original parts and #2 will get the replacement parts. I have tested #1 and got it up and running with test program 1 and 2, They ran perfectly and was a huge relief to see it working.
The only issue I can find with the front panel is that switch 0 has issues turning off unless I push it down harder than the others and it seems about 2 or 3 other switches have intermittent issues turning off.
There with all this feedback I will just respond to it all in sections below.


new_castle_j,
>My best advice is to start in a similar fashion, just the basics.
I did just that and was able to run the two test programs so far. Nothing but the MPU and 8k Static ram installed at the moment.

>>Should I head over to imsai.net and order replacements for all these things?
>I wouldn't, I think you have enough hardware between the two machines to come out with 1 complete one
I may want to sell one at some point but I want to collect opinions on the matter. For all I know people here may have had bad results with them, just looking for feedback, Thanks.

>>One has 10 sockets installed and the other has 14, was this just the preference of the person who built it?
>Could be, the IMSAI mainboards came in an 11 or 22 socket configuration from the factory (the front panel board sits in a socket too) I'm guessing the one you say that has 10 sockets is really 11 if you include the front panel.
Well it seems they are both labeled as 22 socket on the solder masking. I am wondering if it was common to see them with missing connectors like this.

>>Can I use the Tarbell card to get software transferred to them from my laptop?
>I have not personally heard of doing this, but wouldn't rule it out. I think the Altair computer group on yahoo archives tape based software, not sure how it gets loaded back into a system though
As I was writing it I was trying to think of how I will get data onto this machine without drives but I am forgetting about the serial ports I guess. Idk, I brought it up because I've seen it done on an Apple 2e on YouTube but now that I think about it, This is probably just a far fetched idea that is not even possible. It would need many conditions to all line up just right.

>>Any ideas what could be on the two EPROMs labeled MFILL 1.0
>No idea, could be something the previous owner put together, or could just be a bunch of 00s, MFILL kind of sounds like it's just filling up memory space as a placeholder.
That's a possibility I guess, I didn't even think about memory filling, but why two EPROMs for just that?

>> I also have an ASR 33, I would love to hook that up to this some day. IMSAI SIO Card maybe?
>I think that the IMSAI SIO is compatible with a teletype, the manual for the SIO card will be able to confirm
Wow it turns out it does have a current loop hookup. Just need to fix my teletype selector card now but that's a whole other issue.

>>The Dynabyte naked terminal seems to take a parallel keyboard which I don't have, am I better off building a ps2 converter for this?
>I don't have any experience with the naked terminal board, however I would start with serial I/O to a dumb terminal before attempting to use this board.
Hopefully someone on here has one of these and can let me know, but I also don't have a dumb video terminal yet I was hoping this board could be the core of my terminal setup. Logically it should be a simple conversion and I can already imagine one that could be made with 7400 series chips. But I wonder what other owners of this board use.

>>What drives did this Tinker Toys Disk Jokey work with? I can't find any documentation about it
>http://maben.homeip.net/static/S100/morrow/cards/Morrow%20Disk%20Jockey%201%20Controller%201978.pdf
That link has been a GREAT help, with it I even learned that the board also contains a 232 and TTY current loop serial interface! Very cool. Great resource too.

>>I have no software for this system, where do I start?
>There's various archives around the internet, Don Maslin's archvie is good place to start: http://www.retroarchive.org/maslin/index.html
I have a feeling the hardest part will be just finding the stuff for this machine, Thanks for the tip tough.

>>Any top recommended new s100 boards to add(IDE Card Maybe)?
>I don't think you'll be able to answer this question for yourself until to get a little further into the experience.
I have to ask because for all I know there may be some s100computers board that I just have to add that will make life easier or something. I'd never know without asking. If anyone has a favorite board, let me know.

MicrocomputerSolutions,
>Do you intend on running both of the Imsai?
Either I'm running both at one point or I am selling one at some point. I definitely do want to make them both complete with original colored switches I'd say.

>You can move the switch paddles from the incomplete to the almost complete Imsai, and move the parts around to get one complete Imsai.
Good tip, I've moved the three red caps to the one with the regular cord (#1)

>Photos of the insides of both Imsais would be helpful. The one with the funny power cord connector might have a "Universal Power Supply".
I will post a series of close ups late tonight when I get home. I would greatly appreciate any help identifying these two power supplies. They look identical to me, but I don't know what to look out for.

glitch,
>You don't have to worry about upgrading the power supplies to switchers to make it more usable, if the originals work they'll do fine.
Glad to know, thanks.

Besides the test you've outlined, how do I know if the caps are working well enough? I have a scope, I'd assume I need to look for a smooth line on the buses correct?

>The hardest thing to troubleshoot will probably be the front panel.
Thankfully at least on #1 with the exception of a few iffy switches my front panel is in great shape.


>"As mentioned above, be careful when putting power to old tantalum capacitors. Personally, I bring up unknown boards with my bench supply, which has a built in adjustable current limiter. So far that has kept boards brought up that way from exploding tantalums, even when I've had shorted ones."
^
Wow I wouldn't have guessed to test them out of the machine like that. I do have an extra s100 backplane I bought a few years ago that I can hook up to my current limiting supply. I also have a simple riser card but I like that external test idea much better.
I have several questions about this process as I have almost thirty untested boards and I want to be careful about this.
How do I bring up the boards as I test them?
Set the voltage and bring up the current or limit the current low while bringing the voltage up?
Is there any signs I should watch out for? (besides explosions that is)
How long at full voltage until I can safely put a board in the system.
Once I test a board can I be pretty certain that it wont blow op in my system a week later? I believe I heard somewhere (maybe at VCF) That the biggest risk for explosion passes once they have been cycled a few times at voltage.(or am I just making this up?) after that warning I'm a bit nervous is all.

Thanks for all this GREAT feedback. I am already feeling much better prepared to have a great time with these systems.

Here are some pics of IMSAI #1 running after the power tests checked out. the previous owner put masking tape on the right side inside the cover to make the fan draw all its air from over the cards, only issue is they let it show from the front lip, I will have to clean it up a bit.

System waiting at 0000: 34610

Test program 2 running: 346113461234613

Dwight Elvey
December 7th, 2016, 02:00 PM
If you have an older laptop with a parallel printer port you already have
a keyboard.
Most of the S100 parallel keyboard inputs have a jumper to invert the strobe.
If not you can use one of the printer status bits.
No need for a special converter. Just a couple connectors and some wire.
The serial out can go back to the laptop as well, although they most likely used
a video out with the parallel keyboard.
Dwight

ryaninspiron
December 7th, 2016, 03:16 PM
glitch,
Thanks for all the answers, clarification, and tips. I feel pretty well prepared to start testing out all those boards of mine. And it sounds like I should just replace those caps on my North Star board, I may have heard about that in the past but forgot because at the time I hadn't owned any. Those North Star boards sure sound like a liability to me.


Ryan, for what it's worth, I use the John Monahan IBM PC Keyboard to ASCII Converter board to connect to my Dynabyte Naked Terminal. I think these boards are hard to come by because the later Propeller Console IO board works so much better. You might check the retrobrewcomputers.org PCB Inventory to see if any of these boards show up. The manual for the Naked Terminal is also on John Monahan's site and it shows the parallel connections.

> Charles
Thanks for the tip. I will keep an eye out. I can imagine it will be hard to get that board besides having it fabricated myself.
Dwight says I can start off connecting via a parallel port in the mean time, I guess I will build a custom ribbon cable that goes from the connector on the top of the Naked Terminal card to a DB25 connector on the back of the machine. I also have a thermal paper terminal but I'd like to avoid that for general use. What is the connector on the Naked Terminal end of that cable you have in the picture called? Would you happen to have a part number of that connector and also the ribbon cable you used?


The reason that you may have to push down on some of the switches is because of the design of the switches. The mounting bracket for the switch paddles that is prt of the switch is poorly attached to the switch body. Even normal use can cause the paddle mounting bracket to break loose from the main switch body. You may be able to resecure the paddle mounting bracket to the switch body with an adhesive like an epoxy, or maybe careful soldering, but I think most people replace the switches that develop this problem.

When considering additional boards, you need to keep in mind that early S-100 boards and systems do not conform to the IEEE-696 S-100 spec. and may not be compatible with modern S-100 boards without modification to the older boards and system or the newer boards. The Front Panel will only operate correctly with clock speeds of 2 or 3mhz. Most processor boards generate signals that will conflict with those generated by the Front Panel. Unless an aftermarket processor board has a Imsai Front Panel connector and optional jumpers and/or switches, it will not work with an Imsai Front Panel.
I know my Cromemco ZPU card has the connector but does that mean the card will play nice with the front panel?
Also any word about whether the s100computers IDE v2 board works in the IMSAI 8080? I forgot I had picked up that bare board at VCF east last year. I hadn't built it up yet as my Cromemco System two was such a mess. If its compatible I will order the parts for it.


If you have an older laptop with a parallel printer port you already have
a keyboard.
Most of the S100 parallel keyboard inputs have a jumper to invert the strobe.
If not you can use one of the printer status bits.
No need for a special converter. Just a couple connectors and some wire.
The serial out can go back to the laptop as well, although they most likely used
a video out with the parallel keyboard.
Dwight
I do have a laptop I've used for LapLink to a PC-XT in the past. That is a great idea and I didn't even think about the possibility. So in theory I can use my LapLink cable hooked up to a custom DB25 port (installed on the back) to the connector on the Naked Terminal board. Very interesting. That laptop ran Windows XP, what software do I use to send my keyboard over the LPT port? Putty?
I may already have the program(It's been a few years, can't remember and I also have to find that laptop first) but figure I should ask what do you recommend?

As an update when I was taking the pictures of the boards I finally discovered where the model is written.(it was really hidden) They are both the PS-C, So that means 28amp 110v only I believe. Still no explanation why the strange connector but maybe the previous owner just wanted to add a removable cord and this is what they had pulled out of some other device or maybe got from a catalog. Since there's not likely any way I can get that cord replaced I guess I will just add a new one. It still has the rubber grommet in the back from the original cord.
-Thanks

Dwight Elvey
December 7th, 2016, 03:35 PM
You might have to write your own code but it shouldn't be difficult.
You could also just copy conin to lpt1 ( or something like that from a DOS window
I for get the syntax ).
Dwight

glitch
December 7th, 2016, 03:48 PM
I know my Cromemco ZPU card has the connector but does that mean the card will play nice with the front panel?

Yep, it'll work with the front panel. Be aware that the STACK lamp becomes a 2/4 MHz indicator with the ZPU, and you need to have it jumpered to mirror the high and low bytes on I/O accesses.


Also any word about whether the s100computers IDE v2 board works in the IMSAI 8080? I forgot I had picked up that bare board at VCF east last year. I hadn't built it up yet as my Cromemco System two was such a mess. If its compatible I will order the parts for it.

Yes, it'll work, in as far as it's a S-100 board :) It's not compatible with existing IMSAI software, though there are plenty of resources online for getting CP/M up and going with it. I've got a v2 board myself, it's assembled but I haven't put it to use yet. Beware that the v3 board has addressing issues with the GAL on non-Z80 systems, or Z80 systems in which the I/O addresses are mirrored. Doesn't apply to a v2 board, obviously!

Dawsoca
December 8th, 2016, 12:24 PM
Ryan, the connector that goes on the 16 pin edge card connector (Naked Terminal) can be purchased from Mouser (517-3368-0001) 3M Std Edge Card 16P, the ribbon cable and pin socket (517-1M-1010-016-18) Ribbon cable with connector or just the connector if you have ribbon cable (517-1658621-3).

> Charles

MicrocomputerSolutions
December 8th, 2016, 03:41 PM
Your Morrow Disk Jockey/DJ1 was designed to work with 8" single density disk drives. It works with single-sided drives, and the original Morrow CPM that was available separately came on single-sided single-density floppy disk.

I don't know if the DJ1 works with double-sided disks. single sided 8" drives that will work with the DJ1 that I could recommend are the Shugart SA-800/801 MLC/revision 6 or higher with LSI logic board, or Siemens FD-100-8 8" single-sided floppy drive

If you want to try double-sided drives, see if you can find someone who will lend you a working Shugart SA-850/851. You don't want to spend the extra money on double-sided drives, if they won't work with the disk controller you are planning on using. Which Shugart SA-850/851 to get? MLC-12 or higher, preferably MLC-14 or MLC-15.

Dwight Elvey
December 8th, 2016, 04:12 PM
I looked it up:
If you get a video terminal you can use the DOS window command string:

copy con lpt1

I'm assuming it is ltp1. You won't see the reply but if you had two PC, and
one had serial in, you might use that for display with:

copy com1 con

You can only do one at a time. There is the option of a terminal program
but I think these are only serial. Still only might have the option to log
sent data only to a file. It might except LPT1 as a file.

Dwight

ryaninspiron
December 9th, 2016, 05:39 PM
So l have lots of responses and some new questions. Thanks for the input. So first of all here is my two days of responses all in one:


Yep, it'll work with the front panel. Be aware that the STACK lamp becomes a 2/4 MHz indicator with the ZPU, and you need to have it jumpered to mirror the high and low bytes on I/O accesses.

Yes, it'll work, in as far as it's a S-100 board :) It's not compatible with existing IMSAI software, though there are plenty of resources online for getting CP/M up and going with it. I've got a v2 board myself, it's assembled but I haven't put it to use yet. Beware that the v3 board has addressing issues with the GAL on non-Z80 systems, or Z80 systems in which the I/O addresses are mirrored. Doesn't apply to a v2 board, obviously!
glitch, very cool, good to know I can use that other CPU and that I can test my other ZPU boards in a functional machine for a change.
Glad to hear about that IDE board, and I see it was a good decision to pickup that v2 board then. I need to order the parts and build that board up next.
Also on a side note I have a Cromemco 4fdc out of my Cromemco system 2 and I also believe(I need to take a look and confirm it later) that I also have a Persci 277 drive that I haven't touched yet. I hear you have played with that 4fdc for a while, Do you think I could get those running in this IMSAI?(I may just be crazy for it and also I hear they are very temperamental)
I may still go the Disk Jockey w/Shugart Drive route for now, but in the future in terms of using what I have on hand do you think there's a chance?


Ryan, the connector that goes on the 16 pin edge card connector (Naked Terminal) can be purchased from Mouser (517-3368-0001) 3M Std Edge Card 16P, the ribbon cable and pin socket (517-1M-1010-016-18) Ribbon cable with connector or just the connector if you have ribbon cable (517-1658621-3).

> Charles
Thanks Charles, That's great info. I will be ordering those along with the parts for my IDE card then.


Your Morrow Disk Jockey/DJ1 was designed to work with 8" single density disk drives. It works with single-sided drives, and the original Morrow CPM that was available separately came on single-sided single-density floppy disk.

I don't know if the DJ1 works with double-sided disks. single sided 8" drives that will work with the DJ1 that I could recommend are the Shugart SA-800/801 MLC/revision 6 or higher with LSI logic board, or Siemens FD-100-8 8" single-sided floppy drive

If you want to try double-sided drives, see if you can find someone who will lend you a working Shugart SA-850/851. You don't want to spend the extra money on double-sided drives, if they won't work with the disk controller you are planning on using. Which Shugart SA-850/851 to get? MLC-12 or higher, preferably MLC-14 or MLC-15.
MicrocomputerSolutions, Thanks for such concise guidance, I'll start looking out for one of those drives online. It would be cool to see if I can get those persci drives working with the 4fdc as an experiment but this sounds like a much more stable solution. Not to mention probably way easier to find compatible software for.



If you get a video terminal you can use the DOS window command string:

copy con lpt1

Dwight
Dwight, That looks perfect, Thanks. I spent hours last night trying to see if I could catch some activity on my scope after sending that command, couldn't really tell but maybe I need to break out the old hp logic analyzer. I may not be seeing any data on the port since I am not doing a proper handshake that it expects. I am aware that without the handshake the port won't send more than a byte but I cant even get that much without doing something and I'm wondering if that will be a problem for my plan to connect this LPT port right to the keyboard input on the Naked Terminal board.

Update:So two nights ago I toggled in kill the lights. The first time I didn't think it was working because I didn't know what was going on. I failed to realize that shift rate in the block diagram was the rate the leds change. I also didn't realize that the program switches set the game speed. So the first time I started it I thought I did it wrong because nothing was happening. I reviewed my programming from the beginning and confirmed there were no mistakes. After that I had turned on most switches and reset. of course this time the game was running at the speed of light and I still couldn't tell what was going on. then I switched in 02 and suddenly it clicked. I realized I was setting the game speed and finally I was able to play. played speeds 1-8 and called it a night. That was a was really fun though, especially once I had the ah-ha moment and actually started playing. I think playing the game was more enjoyable since it was a reward for all that keying. Way better than simply launching a link or filename.(Seriously)

Yesterday, I spent a good chunk of the evening messing with the scope and my old laptop's parallel port. See above reply to Dwight for more on that.
Also I swapped in the Cromemco ZPU and tested the second test program. All good.

And on a side note while going though my Cromemco System two stuff redescovered some boards I haven't touched in a little while:

First I have a Cromemco 8k Bytesaver 1 that I had jury-rigged to read the much easier to reprogram EEPROM ATMEL AT28c256 34670(It does read from the ATMEL but I haven't setup the write functionality yet, though I really want to do that next.),

A Cromemco 16 KPR with some more PROMs I would love help identifying 34666

and a "rare" Technical design labs VDB, at least acording to the only mention of the board I can find from modern times:
Fairly rare boards Sfeinsmi! in particular few VDB's and SMB-II's were produced That is a cool board since it has a second board pigybacked on the first one. I can imaine finding the software for it will be imposible other than maybe the guy looking for the board in the other post "sfeinsmi". I can't even find a piece of online documentation for it and the only way I even positivly identified it was by reading though scans of old magazines that mentioned the pigybacked design. I can't even find an image of this board online. 3466734669
Maybe I should pm monahan_z to see if he knows any more about the board. The fact he seams to have heard of it means he knows more than me about it already.

Any feedback is greatly appreciated.

Thanks all,
-Ryan

MicrocomputerSolutions
December 9th, 2016, 10:42 PM
Don't buy any floppy drives that come without a warranty. Most 8" floppy drives are 30 years old or older. There are no new replacement parts (only replacement parts come from donor drives). Being able to return a non-working drive is not a warranty, if you have to pay for the shipping, because shipping costs $25-$50 per drive each way.

I sell and service 8" floppy drives, and have been doing this for over 35 years. I warranty my drives for 6-months, and warranty the labor and parts I provide on floppy drive service for six-months. I don't pay the shipping either way either, but I may pay the return shipping, IF I find that I made a serious error when I serviced the drive. I can count the number of drives that were returned under warranty that actually needed repair out of the thousands of drives that I have worked on on one or two hands.

My prices are not the lowest but my drives are the best, and I offer the best warranty. If you find some drives on eBay that you are interested in, I'll be happy to take a look at the eBay ad if you give me the eBay number, and give you my honest opinion. Just don't me every eBay ad number for every 8" floppy drive on eBay. I charge $100-$150 to align and/or repair a single-sided drive, and $150-$200 to align and/or repair a double-sided drive. There are lots of drives for sale on eBay, but from experience, I can tell you that most of those drives don't work, are missing parts, or are out of alignment and need servicing before they can be used. Cheap drives are usually broken, but if they are cheap enough, might be worth buying for parts, or to invest in being fixed. Just don't buy clunkers.

I charge $150-$200 each (plus shipping) for Shugart SA-800/801 single-sided drives and $250-$400 for Shugart SA-850/851 double-sided drives. Availability changes from week to week because I never know how many I'm going to sell, and when I'm going to able to find reasonably priced rebuildable drives. I have a set of Shugart SA-850s in a Compupro Drive Enclosure advertised at $800 on eBay right now. The Compupro Drive Enclosure is worth $300, so the pair of drive is being sold for $500 in the package.

ryaninspiron
December 11th, 2016, 09:14 AM
Don't buy any floppy drives that come without a warranty. Most 8" floppy drives are 30 years old or older. There are no new replacement parts (only replacement parts come from donor drives). Being able to return a non-working drive is not a warranty, if you have to pay for the shipping, because shipping costs $25-$50 per drive each way.

I sell and service 8" floppy drives, and have been doing this for over 35 years. I warranty my drives for 6-months, and warranty the labor and parts I provide on floppy drive service for six-months. I don't pay the shipping either way either, but I may pay the return shipping, IF I find that I made a serious error when I serviced the drive. I can count the number of drives that were returned under warranty that actually needed repair out of the thousands of drives that I have worked on on one or two hands.

My prices are not the lowest but my drives are the best, and I offer the best warranty. If you find some drives on eBay that you are interested in, I'll be happy to take a look at the eBay ad if you give me the eBay number, and give you my honest opinion. Just don't me every eBay ad number for every 8" floppy drive on eBay. I charge $100-$150 to align and/or repair a single-sided drive, and $150-$200 to align and/or repair a double-sided drive. There are lots of drives for sale on eBay, but from experience, I can tell you that most of those drives don't work, are missing parts, or are out of alignment and need servicing before they can be used. Cheap drives are usually broken, but if they are cheap enough, might be worth buying for parts, or to invest in being fixed. Just don't buy clunkers.

I charge $150-$200 each (plus shipping) for Shugart SA-800/801 single-sided drives and $250-$400 for Shugart SA-850/851 double-sided drives. Availability changes from week to week because I never know how many I'm going to sell, and when I'm going to able to find reasonably priced rebuildable drives. I have a set of Shugart SA-850s in a Compupro Drive Enclosure advertised at $800 on eBay right now. The Compupro Drive Enclosure is worth $300, so the pair of drive is being sold for $500 in the package.
I would possibly have been interested in those drives if I wasn't so broke after acquiring the two IMSAIs. They really cleaned out my vintage hardware budget for a while. But I will keep you in mind though for the future because I do see the value in getting a known working/aligned drive.

DEC77
January 27th, 2017, 05:29 PM
If you have the right equipment, you can align an 8" drive. Alignment isn't the only thing that can go wrong with these however. Back in the late '70's I got a DEC RX01 dual 8" floppy drive that "almost" worked. I hung a scope on the output of the read amplifier, loosened the mounting screws for the stepper motor, and then issued a home command, and then a seek to a track in the middle of the drive. I then carefully twisted the motor in its mount for maximum signal on the scope, then locked the motor screws back down. I was able to thus restore the drive(s) to working order. In theory, you need a special analog recorded alignment disk, but the procedure is doable with a known good digital floppy.

MicrocomputerSolutions
January 29th, 2017, 09:58 PM
If you have the right equipment, you can align an 8" drive. Alignment isn't the only thing that can go wrong with these however. Back in the late '70's I got a DEC RX01 dual 8" floppy drive that "almost" worked. I hung a scope on the output of the read amplifier, loosened the mounting screws for the stepper motor, and then issued a home command, and then a seek to a track in the middle of the drive. I then carefully twisted the motor in its mount for maximum signal on the scope, then locked the motor screws back down. I was able to thus restore the drive(s) to working order. In theory, you need a special analog recorded alignment disk, but the procedure is doable with a known good digital floppy.

This works to set the Head Radial, if you have a scope, and a good reference disk. But Head Radial is not the only adjustment that you need to worry about. Index Pulse Timing, and Index Pulse Width are also important, as well as checking the hard stop for TK00 and the TK00 sensor. You need an alignment disk to check and set the Index Pulse Timing and Width. The TK00 hard stop and TK00 Sensor you can adjust using a logic probe (after confirming the Head Radial).