I'd verify the voltages that get output from the psu. you'll need to see around... 12V 5V -5V and -12V, red yellow, blue and white... or was it white and blue? meh.

I've seen computers that won't boot without a battery, though, most pc compatibles tend to boot without a battery if all other conditions are fulfilled .
you definitely need ram for the computer to boot, and since it's a 386sx, it will not be edo, just plain fpm.
most you can expect without ram would be beeps indicating a memory error, if the speaker is still working and hooked up.

oh and looking at the photos... you'll need to fix a lot of traces. all those that seem a little bit off colour should be verified for continuity and repaired.

Explanation of the images,

First image is a closeup of the chip that is above the ISA slot in the third image. I tested all of the pinouts on the side facing ISA and they all connect to vias on the other side of the ISA and they all have continuation. The second image is from the same area as the other images but on the backside of the motherboard.

weedeewee wrote on 2021-12-03, 14:05:

I'd verify the voltages that get output from the psu. you'll need to see around... 12V 5V -5V and -12V, red yellow, blue and whi […]
Show full quote

I'd verify the voltages that get output from the psu. you'll need to see around... 12V 5V -5V and -12V, red yellow, blue and white... or was it white and blue? meh.

I've seen computers that won't boot without a battery, though, most pc compatibles tend to boot without a battery if all other conditions are fulfilled .
you definitely need ram for the computer to boot, and since it's a 386sx, it will not be edo, just plain fpm.
most you can expect without ram would be beeps indicating a memory error, if the speaker is still working and hooked up.

Thank you for the reply!

Ok, I'll add some FPM sticks to rule that out 😀 Doesn't beep without any but measuring the voltages sounds like a good plan to start! Any thoughts on where would be good places to measure? CPU, BIOS chip? How would I know which pins require voltage to measure?

Quick update, I did measure some pins on the CPU, BIOS and ISA and I could get voltages on the pins i tried out - any ideas on something that might fail or be needed in order to startup?

i'd just measure the voltages on the psu connector.
and did you verify the continuity on all those traces that are off-color ?

Look at the small traces on your photos. Some are totally corroded and very likely interrupted. You need to check each of them and - if yes - fix them.

Then you need a POST card for further diagnostics.

I think that needs the vinegar treatment, there's corrosion all around and that small traces that have a dark colour look bad, scrap the varnish and check then.

Here you get an idea what needs to be done 😁

Re: The bet. Can a card in this state be repaired?

Thanks for all the messages! 😀

I did get a ISA POST card to see if it would show anything but it only shows "- - - -" on the displays, no beeping from the piezo speaker either. The LEDS for voltages on the card do light up though, all of them and I could get voltages on chips/cpu etc on the motherboard. But as some of you mentioned, there are probably traces that are somewhere damaged enough to prevent it from booting.

Hoping wrote on 2021-12-03, 19:26:

I think that needs the vinegar treatment, there's corrosion all around and that small traces that have a dark colour look bad, scrap the varnish and check then.

What would be the best procedure for this, can I submerge the motherboard in vinegar or should I desolder as much as possible and just scrub a lot with a toothbrush and vinegar?

Predator99 wrote on 2021-12-03, 21:18:

Here you get an idea what needs to be done 😁

Re: The bet. Can a card in this state be repaired?

This is actually a very good post! Even though mine is not near that bad I get the idea on how to move forward 😀

Hi @doigan
It seems I have the same motherboard. Do you have any info or photo of the whole computer so that I would where it is coming from...
Also did you manage to repair it finally?
Best regards

jasposiris wrote on 2024-03-31, 10:46:

Hi @doigan It seems I have the same motherboard. Do you have any info or photo of the whole computer so that I would where it is […]
Show full quote

Hi @doigan
It seems I have the same motherboard. Do you have any info or photo of the whole computer so that I would where it is coming from...
Also did you manage to repair it finally?
Best regards

Hello @jasposiris

Thank you for your post, I do have more information about this computer.

It's an old Copam 386, model 386SXU/16. I have not seen the brand before but this specific one was in our family during the 90s. I attached two images showing front and back of the case.

Unfortunately I was not able to repair the motherboard by myself, by closer inspection with microscope there were a lot of tracers destroyed even going through to the other side/planes and desoldering the chip shown in the third image with the bad corrosion showed it to be even worse underneath it. So at the moment it is in my storage waiting for a better day, I would really like to get it running again since it has such high personal value for me but for the moment it's out of my knowledge/equipement 🙁

Thanks a lot! Here is pics of my motherboard which is not booting..
386sx 20, ram 72pin edo, trident 8900c VGA chipset and acc micro 2036 chipset.
Yet I only have 3 long beeps when there is no ram, but nothing on the screen unfortunately..

.

edo ram on a 386sx ?

fyi, you should try some fpm.

edited for clarity

weedeewee wrote on 2024-03-31, 16:26:

edo ram on a 386sx ?

fyi, you should try some fpm.

Theseare pictures of the "original" ram found on the board (but maybe it wasn't!).

And I just tested with some ram not labellized edo (so probably fpm picture attached) with no improvement..

jasposiris wrote on 2024-03-31, 17:03:

And I just tested with some ram not labellized edo (so probably fpm picture attached) with no improvement..
IMG_20240331_185226.jpgIMG_20240331_185218.jpg

https://ram-co-shop.de/16-MB-EDO-RAM-60-ns-72 … GM71C17403BJ6_1

still edo

additional. a 386sx only supports up to 16MB or RAM, so try to find some FPM sticks of 1, 2, 4 or 8 Meg size

jasposiris wrote on 2024-03-31, 16:22:

Thanks a lot! Here is pics of my motherboard which is not booting..
386sx 20, ram 72pin edo, trident 8900c VGA chipset and acc micro 2036 chipset.
Yet I only have 3 long beeps when there is no ram, but nothing on the screen unfortunately..IMG_20240330_213731.jpg.

Wow! That sure looks to be the very same motherboard, just a tad faster CPU - impressive! Would you be interested in selling it?