386SX unidentified motherboard diagnosis

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386SX unidentified motherboard diagnosis

Postby GJ5155 on Tue Nov 26, 2019 5:14 pm

Second post, different old computer haha.

This one is a 386SX in a nice case, well I like it because it reminds me of the 386 we had as a family computer in the early 90's.

Unfortunately there is a fault or two. I am getting immediate bios error beeps. 2 short and 8 short which according to the the AMI bios is Circuit Parity Error and a video error (8). At least there is some life in the motherboard, it also made hdd and floppy noises.

When I got it, it was in unknown condition. I found the cmos battery had leaked but it wasn't too bad. Removed battery, cleaned the gunk and checked continuity of the visibly damaged traces and they seem okay.

I've wired in a semi-temporary coin battery holder just in case that is the problem. It is a 3v versus the original 3.6v but this has worked for me in a 486 previously so hopefully its sufficient, eitherway I assumed it would still POST anyway.

It has a IBM 5151 (I think) monochrome monitor, bit of a strange combination but the video card in it looks like it should be able to output to it correctly.
The video car is an ISA based ATi ''Small Wonder Graphics Solution Version 1''. From which I understand they are capable of many output types, MDA, CGA, EGA etc.


There is a display but it is a garbled text, nice green text... but unusable. No readable POST


I have tried swapping the ram in a few combinations but no change.
With nothing plugged in at all I get the same bios errors. With ram combinations, no change.
Cleaned video card contacts but no change.

It is seeming like the video card is faulty but I don't have any other video card to fit (only have the IBM 5155 one which won't fit the slot and another one but it is ISA VLB.

I've only just got back into playing with old computers so don't have a stock pile of parts unfortunately, I've tried trademe and the local computer recycling place but nothing.

Does any one have any suggestions for something else to try?
Failing that, does anyone have an ISA video card they would sell please?
Does anyone recognise the motherboard? It has 386SX/PI written on it but I can't find anything on it.




Thanks in advance
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Re: 386SX unidentified motherboard diagnosis

Postby GJ5155 on Tue Nov 26, 2019 5:18 pm

A couple more photos
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Re: 386SX unidentified motherboard diagnosis

Postby LS120 on Sat Nov 30, 2019 4:07 pm

the first thing to do is remove the battery, then remove the keyboard connector and replace that.. while it's out check the tracks and the bios socket if by battery.. as there could be problems under the socket.. i have done a 286 and it boots after the repairs.. look at my 286 blog on here.. but it will take time and a good eye.. also a fiberglass pen for the tracks..
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Re: 386SX unidentified motherboard diagnosis

Postby LS120 on Sat Nov 30, 2019 4:11 pm

also it looks alot like a ABC case..
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Re: 386SX unidentified motherboard diagnosis

Postby GJ5155 on Wed Dec 04, 2019 8:47 am

LS120 wrote:the first thing to do is remove the battery, then remove the keyboard connector and replace that.. while it's out check the tracks and the bios socket if by battery.. as there could be problems under the socket.. i have done a 286 and it boots after the repairs.. look at my 286 blog on here.. but it will take time and a good eye.. also a fiberglass pen for the tracks..

Cheers for the reply, I had already removed and cleaned up the area around the battery. A couple of traces didn't look great but a continuity test showed they are okay.

I salvaged a coin battery holder from a dead motherboard soldered it away from the board. Only 3v but works fine.

The double then 8 beeps was still there. I swapped the ram and video card and its working now! Have installed DOS 6.22 then installed Win3.11 and played a few old games.
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Re: 386SX unidentified motherboard diagnosis

Postby GJ5155 on Wed Dec 04, 2019 8:48 am

Sopwith 2
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Re: 386SX unidentified motherboard diagnosis

Postby LS120 on Fri Dec 06, 2019 4:27 pm

if you are going to keep the unit i would still remove the keyboard chip and connector and replace them.. as its the un-seen that will cost in the long run.. and the battery damage around that area may come back to haunt you again..
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