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huubwen
July 20th, 2012, 06:25 AM
I have bought an IBM AT 5170 mainboard with CPU and memory. The mainboards looks clean and well cared for.

Today I build it into a case and powered her up. Nothing happens. Well, the power supply spins continuously but no beeps or screen output at all. Nothing was connected to the mainboard. I have tested as well with a Hercules card en a VGA card.

The only thing that happens is that the num-lock, caps-lock and scroll-lock lights flash once when powering up.
I have also swapped the memory modules from bank 0 to 1 and 1 to 0. No change.

I grapped my multi meter and start testing the caps. I didnít find any faulty caps.

Next I saw an object on the board that leaked badly. (see pictures) I measured its resistance. It was not conducting any power at all.

Could this be the problem? Can I remove this object and short-circuit it for testing the board?

What else could be the problem?
97129713

ChrisCwmbran
July 20th, 2012, 06:36 AM
According to my information, Y2 is a "12Mhz XTAL" crystal oscillator in which case I'd think its a fairly necessary part.

I'm sure one of the more clever guys on here will be able to tell you far more than that.

DOS lives on!!
July 20th, 2012, 06:37 AM
I'd clean the corrosion from that area first then see if that makes a difference. It could also be a bad RAM chip causing no video output or POST beeps. Even though you interchanged the memory chips, there could still be a bad chip in either bank causing the problem. To solve that, you're just going to have to remove each memory chip at a time and see if it cures the problem. I had the same no video problem on my AT. It turned out to be a bad chip in Bank 0. Time consuming, but well worth it.

ChrisCwmbran
July 20th, 2012, 06:47 AM
In fact if I am reading it right, Y2 is the main clock crystal for the CPU with its output being fed through an 82284 clock driver chip, which halves that 12Mhz frequency to form the clock speed for the 286 CPU.

Personally I'd clean up the mess around it with a dry brush and see if you can see anymore about it.

huubwen
July 20th, 2012, 07:18 AM
I have cleaned up the mess. I was quite easy. It fall off in one big chunk.
Unfortunately the numbers on the crystal where worn away by the leaking. I cannot read anything off the crystal.
9714

ChrisCwmbran
July 20th, 2012, 07:20 AM
I'm by no means an expert but I'm not convinced that mess came from inside that oscillator.

I don't suppose you have an oscilloscope?

huubwen
July 20th, 2012, 07:23 AM
No, I don’t have an oscilloscope. :(

ChrisCwmbran
July 20th, 2012, 07:26 AM
Is the power supply in the case you are using known to be good?

Have you checked the voltages it is outputting?

Chuck(G)
July 20th, 2012, 07:31 AM
Y2 present or absent won't affect the ability of the board to boot. It's a 32.768KHz crystal for the MC146818 CMOS clock/NVRAM (you can find these crystals on modern motherboards--they're not uncommon). The corrosion was probably from the battery in the 5170 leaking.

With the power on, measure the voltages at the motherboard connector. You can find the pinout here (http://pinouts.ru/Power/MotherboardPower_pinout.shtml)

huubwen
July 20th, 2012, 07:54 AM
Well, here are the readings. Those readings were taken with only the mainboard connected to the power supply.

P8
1 1,25
2 5,06
3 12,72
4 -12,16

P9
3 -5,11
4 5,06
5 5,06
6 5,06

I am not using the original IBM AT power suply but on old clone.

huubwen
July 20th, 2012, 08:17 AM
I start verifying the J18 RAM jumper setting as mentioned on the 5170 vintage-computer wiki.
I could not locate a J18 jumper on my type 2 mainboard.
I did find a J10 jumper (see picture). It is not jumpered. Should it be this way?
9716

Chuck(G)
July 20th, 2012, 08:31 AM
Well, here are the readings. Those readings were taken with only the mainboard connected to the power supply.

P8
1 1,25
2 5,06
3 12,72
4 -12,16

P9
3 -5,11
4 5,06
5 5,06
6 5,06

I am not using the original IBM AT power suply but on old clone.

It looks as if your "Power good" line is not rising to the occasion. If you've got a 1K or so (anything between 220 and 2K ohms should do) resistor, try removing the PSU lead from pin 1 on P8 and jumpering pin 1/P8 to pin 2/P8 to get a logic high. I'm not certain that it'll do any good, but it stands out as an issue.

huubwen
July 20th, 2012, 11:14 AM
I found the problem. :D

Although the (clone) power supply did work properly on another XT286 board it did apparently not on the IBM AT board. The power good voltage was too low to get the cpu out of the reset state.
I used another power supply from a Pentium class system and the AT board did POST at once. It nicely counts 640 KB and then displays a whole bunch of errors. Obliviously because it had only a MDA card connected an no keyboard, floppy, battery pack etc.

Any guesses why the power supply did not work on the 5170 mainboard?

Chuck(G)
July 20th, 2012, 11:34 AM
By "XT286" do you mean a real 5162 or just a clone? Lots of clones don't rely on the PG signal, but rather generate their own by delaying reset until +5 has been stable for an appropriate time. I'm not certain what the 5162 does.

wdegroot
July 20th, 2012, 11:47 AM
strange but true. some of the IBM AT systems had a BOX in the lower drive bay
It was a load resistor
try plugging in a hard drive, you likely will not need the controller card
the clock battery area often gets crusty and needs cleaning
if it is really bad
hot water followed by shgaking blowing off
and put aside for several days
( small crvices can retain water)
the ocillator does not have anything in it to leak.
remeber the drive table in the IBM AT is very limited
even the seagate st-251 si not supported
when I was at INTEL DIV in 88, they claimed that " the last of the AT-286" did have an expanded drive table.
But I sent one out for repair and they substituted a clone phoenix bios. THIS IS likely not your current problem
there si a switch a small slide switch =on the mb.
to sent monp/color. If you only get a cursor that could be the problem.
Unlike the pc/xt a vga card should work and the cards and monitor are easier to find. Re,ener that the IBM AT supported 360 and 1.2 meg floppies but possibly not the 1.44 floppy.
the setup/.exe or setup.com from phoenix should wotrk
also remeber there si NO SETUP in bios
you must boot from a disk.

Chromedome45
July 20th, 2012, 12:49 PM
The second picture shown in the original post is a genuine XT-286 board froma 5162. I used to have one just like it.

Chuck(G)
July 20th, 2012, 01:50 PM
The second picture shown in the original post is a genuine XT-286 board froma 5162. I used to have one just like it.

I'm not certain (schematic is hard to read), but the PG on the 5162 may have a 10K pullup on it, which would explain a lot.

modem7
July 20th, 2012, 02:24 PM
strange but true. some of the IBM AT systems had a BOX in the lower drive bay
It was a load resistor
It is written about in the IBM 5170 wiki entry in these forums:
http://www.vintage-computer.com/vcforum/showwiki.php?title=Systems:IBM+PC+AT+5170

huubwen
July 21st, 2012, 02:19 AM
Well, next problem.

I plugged the original IBM MFM controller card and a VGA card into the board. I also connected a ST-225 to the MFM card and a 1,2MB floppy drive as well.
I booted the 5170 advanced diagnostics 2.07 from the floppy and configured the date/time and system parameters. I configured one fixed disk as type 2.

At boot it always displays 1782-Disk Controller Failure and sometimes 601-diskkete error. Nevertheless the floppy drive works fine. It displays no further errors.
Because I do not poses a genuine MFM control cable I use a floppy cable (straight, untwisted) and connect the drive B: part to the ST-225. The ST-225 is jumpered as drive 0.

I am sure the ST-225 is working. It comes from another working system.

The advanced diagnostics allows me to manual add option 17 (fixed disk and controller). From there I can get to the low level format menu. The drive does nothing when asked to low level format the drive.

The LED of the ST-225 does not lid up at all. Only when I choose the option to move the system. It then lids up but the advanced diagnostics displays an error that preparing the system for transport failed.

What am I missing here?

Stone
July 21st, 2012, 03:33 AM
1782 is a 'Fixed disk controller failure' so I'm not suprised you are not able to LLF the drive. You need to try another hard drive controller.

modem7
July 21st, 2012, 04:06 AM
At boot it always displays 1782-Disk Controller Failure and sometimes 601-diskkete error. Nevertheless the floppy drive works fine. It displays no further errors.
Because I do not poses a genuine MFM control cable I use a floppy cable (straight, untwisted) and connect the drive B: part to the ST-225. The ST-225 is jumpered as drive 0.
Has the controller card been plugged into an 8-bit slot rather than a 16-bit slot ? It's just a quick guess.

Do the jumpers match those in the photos at http://www.minuszerodegrees.net/5170/cards/5170_cards.htm

huubwen
July 22nd, 2012, 12:07 AM
The controller card is placed in a 16-bit slot. Itís in fact the second generation of the controller as mentioned at http://www.minuszerodegrees.net/5170/cards/5170_cards.htm. The jumpers are in the same position as the image.

Although the controller is still not working I think I do have resolved another mystery. I strongly think it is not an IBM 5170 AT mainboard but a IBM 5162 XT286 board.

Although I bought the board as an AT board I think a IBM XT286 board is a lot more interesting.
* The board has three 8-bit slots instead of two.
* The board has a CR-P2 battery in a proper battery holder
* The resemblance to the pictures found on http://www.nadbor.pwr.wroc.pl/yesterpc/Hardware/ISA%20motherboard/IBM%20XT286/slideshow/IMG_3576.JPG is strong.

huubwen
July 22nd, 2012, 12:26 AM
The controller card is placed in a 16-bit slot. Itís in fact the second generation of the controller as mentioned at http://www.minuszerodegrees.net/5170/cards/5170_cards.htm. The jumpers are in the same position as the image.

Although the controller is still not working I think I do have resolved another mystery. I strongly think it is not an IBM 5170 AT mainboard but a IBM 5162 XT286 board.
Although I bought the board as an AT board I think a IBM XT286 board is a lot more interesting.
* The board has three 8-bit slots instead of two.
* The board has a CR-P2 battery in a proper battery holder
* The resemblance to the pictures found on http://www.nadbor.pwr.wroc.pl/yesterpc/Hardware/ISA%20motherboard/IBM%20XT286/slideshow/IMG_3576.JPG is strong.

huubwen
July 22nd, 2012, 03:08 AM
The controller card is placed in a 16-bit slot. It’s in fact the second generation of the controller as mentioned at http://www.minuszerodegrees.net/5170/cards/5170_cards.htm. The jumpers are in the same position as the image.
Although the controller is still not working I think I do have resolved another mystery.
I strongly think it is not an IBM 5170 AT mainboard but a IBM 5162 XT286 board.

Although I bought the board as an AT board I think a IBM XT286 board is a lot more interesting.
* The board has three 8-bit slots instead of two.
* The board has a CR-P2 battery in a proper battery holder
* MSD reports it as an IBM XT286

huubwen
July 22nd, 2012, 04:44 AM
I think I made some progress in finding the faulty component.
I did a resistance check on the bare mainboard with nothing connected to it. I did the same test with a clone XT board. Here are the readings:

IBM XT286
+5V 14,6 ohm
-5V to high to read
+12V to high to read
-12V to high to read

XT Clone
+5V 161 ohm
-5V to high to read
+12V to high to read
-12V to high to read

It appears to me that the board has a +5V problem after al.
No blame to the power supply that would not raise the power good signal :)

I have done a resistance check on all 3 leg tantalum caps on the board.
All caps have about the following readings:
Pin 1-2 14,8 ohm
Pin 1-3 0,03 ohm
Pin 2-3 14,8 ohm
Looks good to me.

My questions:
1. With only 14,6 ohm resistance at the +5V how is it possible that the Pentium class power supply powered the board without problems and the board works fine?
2. It appears there is no faulty tantalum cap on the board. What else is likely to be the problem?

Stone
July 22nd, 2012, 04:56 AM
Not to sound like an echo, the HD controller is bad.

Chromedome45
July 22nd, 2012, 06:31 AM
The controller card is placed in a 16-bit slot. It’s in fact the second generation of the controller as mentioned at http://www.minuszerodegrees.net/5170/cards/5170_cards.htm. The jumpers are in the same position as the image.
Although the controller is still not working I think I do have resolved another mystery.
I strongly think it is not an IBM 5170 AT mainboard but a IBM 5162 XT286 board.

Although I bought the board as an AT board I think a IBM XT286 board is a lot more interesting.
* The board has three 8-bit slots instead of two.
* The board has a CR-P2 battery in a proper battery holder
* MSD reports it as an IBM XT286

I mentioned that in an earlier post that the picture was of an XT-286. But I feel that the HD contoller is bad as well.

Stone
July 22nd, 2012, 07:30 AM
I mentioned that in an earlier post that the picture was of an XT-286.Why is it that when some people ask for help or suggestions they either ignore or don't read the responses that are posted to give them the information they need to get the result they are looking for?

SpidersWeb
July 22nd, 2012, 01:03 PM
Testing the resistance of capacitors while they're in circuit will not identify the faulty part, because they're mostly linked in parallel. If you have a capacitor that is shorted, and five others that aren't, all 6 will show 0 ohms if they're in parallel on the same circuit (even if only one of them is actually bad).

If what you've said is accurate, then it sounds like the power good circuit of the PSU isn't working 100%.
It's different from overload protection, it just fires up when the PSU has got it's voltages nice and sorted.

14.6 seems too low, but if the fan on the PSU kept spinning, then that's fine.

modem7
July 23rd, 2012, 01:49 AM
14.6 seems too low, but if the fan on the PSU kept spinning, then that's fine.
A spinning PSU fan is no guarantee that a PSU is outputing all voltages/signals correctly.

modem7
July 23rd, 2012, 01:51 AM
I suspect that you are measuring incorrectly. The way it is measured is shown [here (http://www.minuszerodegrees.net/5150_5160/MDC/no_beeps_2_2.htm)] but note that that the resistance measurements on that web page are for the 5150 motherboard and 5160 motherboard (with no cards fitted).
But why are you measuring resistance? You would only do that if one or more of the voltages ( +5V / -5V / +12V / -12V ) does not measure per specifications.

On the assumption that your non-IBM power supply may be outputting a fake POWER GOOD signal, I did some experiments with a 5170 motherboard and a first generation 5170 hard/floppy controller. The experiments revealed that to pass the 1782 check, the motherboard and controller only require +5 volts.

I'm quite positive that a 5162 motherboard and second generation hard/floppy controller would do the same. You have checked the controller jumpers. If the +5 volts is within tolerance, then the probability is very high that your controller is faulty.

I think it unlikely that your VGA card would be conflicting with the controller.

huubwen
July 23rd, 2012, 02:45 AM
But why are you measuring resistance? You would only do that if one or more of the voltages ( +5V / -5V / +12V / -12V ) does not measure per specifications.

The reason for the measuring is that the power supply gave a good +5V power good signal using another motherboard. With the IBM 5162 motherboard the power good did not raise and the board did no post.
I indeed used the instructions on http://www.minuszerodegrees.net for the resistance measurement.
Because the 5V resistance was very low compared to a working 5150 or 5160 mainboard I suspect a problem with the 5162 board.

modem7
July 23rd, 2012, 03:24 AM
Because the 5V resistance was very low compared to a working 5150 or 5160 mainboard I suspect a problem with the 5162 board.
I just measured three 5170 motherboards (without fitted cards). The +5 volt resistance ranged from 300 to 600 ohms.

Maybe, because of +5 volt overloading (due to partial short on motherboard), the +5 volts is below spec, and not low enough to affect motherboard operation, but low enough to affect the controller (i.e. I'm suggesting that the controller may be more sensitive to +5 volt level than motherboard).

What does the +5 volts measure?

huubwen
July 23rd, 2012, 03:42 AM
What does the +5 volts measure?

Resistance:

+5V 14,6 ohm
-5V to high to read
+12V to high to read
-12V to high to read

Voltage:

P8
1 1,25 (power good)
2 5,06
3 12,72
4 -12,16

P9
3 -5,11
4 5,06
5 5,06
6 5,06

modem7
July 23rd, 2012, 04:45 AM
P8
1 1,25 (power good)
2 5,06
3 12,72
4 -12,16

P9
3 -5,11
4 5,06
5 5,06
6 5,06
Hang on. Those were the measurements you made back at post #16. That is when you had the first power supply fitted. +5V, -5V, +12V, -12V were all good. For some unknown reason, the POWER GOOD signal was not being driven high enough, resulting in the motherboard not starting.
It is interesting to look at the earlier measurements though. If there is a partial short on the +5V line of your 5162 motherboard, then the fact that the +5V line was sitting at +5V indicates that the first power supply was able to cater for it.

You then discovered that a 'Pentium class power supply' you have allowed the motherboard to start, however, using that power supply you always see a 1782 error. That is where we are now. What does the +5 volts measure when the 'Pentium class power supply' is used?

huubwen
July 23rd, 2012, 06:04 AM
Hang on. Those were the measurements you made back at post #16. That is when you had the first power supply fitted. +5V, -5V, +12V, -12V were all good. For some unknown reason, the POWER GOOD signal was not being driven high enough, resulting in the motherboard not starting.
It is interesting to look at the earlier measurements though. If there is a partial short on the +5V line of your 5162 motherboard, then the fact that the +5V line was sitting at +5V indicates that the first power supply was able to cater for it.

You then discovered that a 'Pentium class power supply' you have allowed the motherboard to start, however, using that power supply you always see a 1782 error. That is where we are now. What does the +5 volts measure when the 'Pentium class power supply' is used?

Your summary is correct.
I will post the complete readings on the P8 and P9 connector with the Pentium class power supply soon.

huubwen
July 23rd, 2012, 07:24 AM
Here are the readings with the pentium class psu connected to only the 5162 board:

P8
1 4,64V (power good)
2 5,07V
3 12,31V
4 -11,61V

P9
3 -4,87V
4 5,07V
5 5,07V
6 5,07V

huubwen
July 23rd, 2012, 10:04 AM
Some new information about the MFM controller problem.

I put the untouched MFM controller in a 486 DX2 system and connected the ST-225 to it with the same cables in untouched configuration. I set the disk type to 2 in the modern Award BIOS.
It gave me a harddisk error at the POST. I ignored it and used SpeedStor to do a low level format. The format wend without any problems. Fdisk correctly sees the disk and I can format and use it.
After the low level format and at the next reboot the harddisk error wend away and I booted successfully from the ST-225 with no errors.

Next I put the MFM controller back in the 5162 board. And guess what; still “1782-Disk Controller Failure”. Only the floppy part of the controller works in the 5162.

So I think we can rule out the MFM controller, cables or the disk as faulty.

Chuck(G)
July 23rd, 2012, 10:37 AM
Measuring resistance on a motherboard power supply line can only convey information if you're looking for a dead short-circuit or nearly one--or an open circuit because of a bad trace or solder joint. Since you're measuring into a mass of nonlinear devices, anything much above 100 ohms doesn't really convey any useful information.

Has anyone looked at the BIOS listing for the 5162 to see exactly what a 1782 error is the result of? In other words, what test is being performed on the controller that results in this error?

huubwen
July 23rd, 2012, 11:02 AM
Has anyone looked at the BIOS listing for the 5162 to see exactly what a 1782 error is the result of? In other words, what test is being performed on the controller that results in this error?
If someone is willing to look than this are the BIOS chips used on my 5162 board:
U34 78X7460
U35 78X7461

I also checked the 5162 board with a 16 BIT IDE controller card and a modern 60GB drive with dynamic drive overlay.
This works flawlessly. No errors when using the disk and also no 1782 error.

modem7
July 23rd, 2012, 12:23 PM
So POWER GOOD and all voltages okay.

So if there is a partial short on the +5V line of your 5162 motherboard, then both power supplies are dealing with it.

I haven't time to look through the 5162 technical reference now (on [this (http://filedump.glitchwrks.com/manuals/IBM/techref/5162/)] link), but I have no doubt that the 1700 series checks (hard drive) will be the same as those for a 5170. The first check is the 1782, where the POST asks the controller to do a self check. A 1782 is posted if the controller responds in the negative, or the controller does not respond. See [here (http://www.minuszerodegrees.net/5170/post_errors/5170_post_errors.htm)] for details.

The new information about the controller working in a 486 DX2 system in very interesting.

The symptoms/results though can be explained by the slot on the 5162 not having all signals. Damaged by corrosion? Does use of all 16-bit slots result in the 1782 error?

huubwen
July 23rd, 2012, 09:39 PM
Does use of all 16-bit slots result in the 1782 error?

I swapped the MFM controller and VGA card trough the 5 available 16-bit slots. The results are interesting.

At first it gave me no errors at all on post using the MFM card in slot 2 or 3! Although there were no errors, it would not boot from disk.
I continued using other slots and the 1782 and/or the 601 errors reappear.
I changed back to using slot 2 and 3. It gave me again a 1782 and/or 601 error. After further testing it didn’t work anymore and keeps displaying 1782 In all slots sometimes accompanied by error 601.
The VGA card does work in all slots in all conditions.

I don’t know if it is a problem but the 5162 boots very fast when powering up. The ST-225 spins up slowly and needs a few seconds to complete its power on self-test. (seek test etc.).
When the ST-225 has to power up from a complete halt it appeared to me it didn’t complete its self-test yet at the point that the controller gets the command to execute its own self-test.

modem7
July 23rd, 2012, 11:18 PM
My experiments on a 5170 with first generation controller reveal:

1. If the controller is placed in an 8-bit slot, the 1782 passes, but the next test, the 1780, fails.

2. The 1782 test passes even when there are no hard drive cables attached to the controller (but the next test, the 1780, fails).
That suggests that the controller's self test does not rely on the presence of a hard drive. This is what I would expect.


I donít know if it is a problem but the 5162 boots very fast when powering up. The ST-225 spins up slowly and needs a few seconds to complete its power on self-test. (seek test etc.).
When the ST-225 has to power up from a complete halt it appeared to me it didnít complete its self-test yet at the point that the controller gets the command to execute its own self-test.
From item 2 above, if the drive were not ready, we would expect a 1780 error, not a 1782.


At first it gave me no errors at all on post using the MFM card in slot 2 or 3! Although there were no errors, it would not boot from disk.
The failure to boot when there were no 1700 series errors may be due to an unrelated cause.
Best to first hunt down the cause of the 1782.


After further testing it didnít work anymore and keeps displaying 1782 In all slots sometimes accompanied by error 601.
So you don't have any choice now but hunt down the cause of the 1782.

It's like you have a bus related issue, one that affects the hard/floppy controller, but not the VGA card.

Chuck(G)
July 24th, 2012, 09:25 AM
Since there's been nothing but jabber about the 1782 error, I decided to take a couple of minutes and look at the 5162 BIOS and see where the 1782 originates.

Well, if you look in the DISK-SETUP routine, anything that jumps to the tag CTL_ERRX will cause the error message. That appears to be only the section that issues an INT 13H, function 14H, "execute controller diagnostic". That routine, CTRLR_DIAGNOSTIC, is very simple. It sets up the PICs for an interrupt, waits for a busy status on the controller to clear and then issues a 90H command to the card and waits for it. If the card clears busy and returns no error, the code declares the controller good.

So, what might cause the controller to fail? The NOT_BUSY routine is a simple CPU loop waiting for the busy bit to clear, so no problem there.

Going to the schematics of the hard/floppy controller, about the only thing that jumps out is the requirement for +12 and +5 on the bus. If your +12 is wonky, then things are not going to go well.

About the only thing that could cause both a 601 and a 1782 error is that the PIC isn't getting the interrupts. Since the diskette section uses IRQ 6 and the hard disks section uses IRQ 14, they're not even on the same connector; the likelihood of both failing is small.

Have you looked at the CPU crystal? If someone wanted to "hot rod" this board (very common back then), that would cause all sorts of CPU-dependent timing loops to go screwy.

huubwen
July 24th, 2012, 11:53 AM
Since there's been nothing but jabber about the 1782 error, I decided to take a couple of minutes and look at the 5162 BIOS and see where the 1782 originates.
Thank you for sorting out.

Have you looked at the CPU crystal? If someone wanted to "hot rod" this board (very common back then), that would cause all sorts of CPU-dependent timing loops to go screwy.
I have visually inspected the component which I believe is the CPU crystal (see picture). It seems untouched to me.
Somehow I believe the partly shorted +5V on the board must be related to the problems with the MFM controller card. As you described a stable +5V and +12V on the bus is required by the card.
Any suggestions how to find the partly +5V short?
9739

mikey99
July 24th, 2012, 02:12 PM
Have you tried cleaning the edge contacts on the MFM card ? I've had several problems
recently with ISA and MCA cards that a simple cleaning with a new pencil eraser , solved
the problem.

Just rub the eraser over the contacts a few times, and wipe off with a clean rag.

Chuck(G)
July 24th, 2012, 02:46 PM
I have visually inspected the component which I believe is the CPU crystal (see picture). It seems untouched to me.
Somehow I believe the partly shorted +5V on the board must be related to the problems with the MFM controller card. As you described a stable +5V and +12V on the bus is required by the card.
Any suggestions how to find the partly +5V short?

The crystal is the correct frequency. What bothers me is your statement that the POST is very fast. That's not my experience with the 5170; I don't think it should be any different with the 5162.

Have you tried running a RAM diagnostic for a few hours on the system? There's something that's not quite right.

My next step would be to inspect the PCB for a possible bad solder joint. After that, it'd be removing each of the socketed ICs one by one to see if a marked difference in the resistance reading is noticed. After that, it'd be to replace the electrolytic and tantalum capacitors one by one. Not something for the faint-of-heart.

Can you burn your own EPROMs? If so, I have a diagnostic ROM set for the 5170 that might turn something up.

huubwen
July 24th, 2012, 09:38 PM
Just rub the eraser over the contacts a few times, and wipe off with a clean rag.
Miket99 you made my day :D

I grabbed a pencil eraser and I thoroughly cleaned the contact of the MFM card. And guess what; it didn’t give any error at all. It will not fail anymore even after multiple power offs.

The self-test of the ST-225 changed to. It spins up and does just two seeks. That’s it. No complete seek test anymore.

I successfully installed FreeDOS. Man; what is that 286-6 way faster than my 5160.

I'm still not completely convinced yet but it looks very promising.

Altought the MFM card works now I am still determent to find the partly short at the +5V line.
I will follow the steps as suggested by Chuck(G).

Chuck(G)
July 24th, 2012, 09:47 PM
As I said earlier, I didn't think there was a partial short. Normally, if this were the case, you could identify the component just by feeling around for heating.

Don't use the pencil eraser trick more than once--the plating on those contacts is very, very thin (a few microns) and an abrasive eraser will take it off in only a few iterations. Get some good contact cleaner, such as DeOxIt. You'll also be able to clean the edge connectors themselves that way.

modem7
July 25th, 2012, 01:56 AM
Miket99 you made my day :D
I grabbed a pencil eraser and I thoroughly cleaned the contact of the MFM card. And guess what; it didnít give any error at all. It will not fail anymore even after multiple power offs.
Well done Mikey.

huubwen
July 25th, 2012, 05:46 AM
As I said earlier, I didn't think there was a partial short.
Because I do not experience a problem (except for the board not working with all my power supplies) I decided not to take any further action with the board and just enjoy it.

Next step for is finding an original IBM XT286 case to put the 5162 board in. Finding it would be a real challenge.

Thank you all for your help

mikey99
July 25th, 2012, 11:30 AM
Glad to hear that cleaning the edge contacts on the MFM card fixed the problem !

I just happen to have a 5162 motherboard here, and I measured the +5 pin resistance
with no cards plugged into the motherboard. Using my Simpson 260 (old analog meter)
I read about ten (10) ohms between the +5 connector pins and the ground pin.
Using Ohms law I=E/R, this translates to about .5 amps or 500 ma. This does sound
a bit high for current draw on the motherboard, but still well within spec.... I would
think the +5 V power supply would be capable of handling several amps draw on the +5
line. Using the resistance value measured with a meter may not be that accurate of
a way to calculate the true current.

I last powered this board up about two years ago, and it worked fine then.

Chuck(G)
July 25th, 2012, 01:28 PM
The resistance is irrelevant if it's not a short or open. You're measuring a non-linear circuit, so the resistance is going to depend upon the supply voltage in your meter and the input impedance (the 260 will have a much lower impedance than almost any DMM). So, you'll get two very different readings depending on the polarity of the measurement (which probe goes to which side) and the measurement voltage (does your meter have a "diode" setting that uses higher voltage?). Add to that the time elapsed to allow the decoupling capacitors to charge, any leakage resistance, the forward drop of any protective diodes, etc. and you're not going to wind up with a "If it measures X ohms, it's good" type of test.

A dead short's a dead short, however.

wdegroot
August 2nd, 2012, 06:23 PM
remeber if the second wire on one of the connecors is not there try another supply
the drive will need to be llf for an AT not an xt -different format
this runs agains the grain but ANY similar or eben an advanced wd11006 ( 1:1 card will work. One morning I was called as someone had been robbed? I just plugged in the nearest wd1003 type care in and the system worked. The typical wd card is very close.
just dont try a 1:1 llformatted drive with an older card.
sometimes it is simpler to use a third party program like wdformat wdfmt.exe ? if the cmose is set right.,
this next may be heresy. but later bios chips work in AT and AT clones. did it not theory.