Some motherboards require healthy bios battery to post. So that is worth a shot.

If the label on the bios chip is any good then it seems to be a newer bios version than is available on theretroweb.
Getting a dump of that would be appreciated.

Agreed on the testing with a cmos battery first.
Also check to see what post code it gives without any ram and different ram if possible.

Also, add a speaker to listen for beep codes.

A few longshots:
Try another BIOS chip with an older BIOS version, even if you successfully dumped the current one.
Check the frequency of the XTALs.
Check activity on ISA data and address lines.

- Xtals and osc are fine.
- CMOS battery, circuit ok but nothing change.
- Speaker, total silence.

I will try with BIOS images (https://theretroweb.com/motherboards/s/ecs-wh386sx) and (https://theretroweb.com/motherboards/s/ecs-wh386sx-wh386sx-d).

Since I can dump the BIOS that came with the motherboard, I don't think that's the problem, but I'll try.

I think the motherboard is dead...

RafaelBR wrote on Yesterday, 20:28:

Since I can dump the BIOS that came with the motherboard, I don't think that's the problem, but I'll try.

Please do dump the bios.

In the photos the post code it gets stuck on is 41. Does this come on immediatly or does it show other post codes before it gets stuck on that and is it the same without any ram ?

RafaelBR wrote on Yesterday, 16:12:

- I tried turning it on without the cache ICs.

Was here also a jumper you had to change to tell it no cahe?

Is there a short on the reset switch (i.e. does the board think the reset switch is constantly pressed in?

weedeewee wrote on Yesterday, 21:02:

In the photos the post code it gets stuck on is 41. Does this come on immediatly or does it show other post codes before it gets stuck on that and is it the same without any ram ?

Error code 41 occurs the exact moment the board is powered on.

The previous code is 01.
With or without memory, the same thing happens.
The IRDY LED lights up and goes out immediately...

I checked the board with a thermal camera; only the W83C312F doesn't show any heat. I couldn't find a datasheet for it, but I can detect that it's being powered with 5V.

NeilKnows wrote on Yesterday, 21:13:

Was here also a jumper you had to change to tell it no cahe?

No, only size. 64 ou 32Kb

With or without cache, it's the same thing. It could be a faulty cache IC, but it's not impossible.

NeilKnows wrote on Yesterday, 21:13:

Is there a short on the reset switch (i.e. does the board think the reset switch is constantly pressed in?

There is no short in the reset. When the reset button is shorted, the reset LED on the diagnostic board lights up, resets the numbering, and returns to 41...

If I understand you initial post correctly, the board died approximately at the moment you connected the keyboard. It sounds like you connected the keyboard while the system was powered on. This is an operation people tell you not to do, because there is no proper power sequencing (GND and +5V pins making connection before the data pins) on the AT keyboard connector. While I also did connect keyboards while a system was powered on without ill effects, the danger oftentimes quoted: "Connecting an AT keyboard or a PS/2 mouse with the system turned on will likely damage your system" possibly sometimes is real. The keyboard connects to the Intel 8042 auxilliary processor IBM introduced with the IBM AT, which is usually called "keyboard controller", but actually does some more auxilliary jobs controlling the AT platform, and is essential for a well-behaving system. It's possible that the issues you are facing now are due to a broken keyboard controller.

If you have another 286/386/486 board that does not have a PS/2 mouse port or a pin header for a PS/2 mouse port, try using the keyboard controller from that board instead of the keyboard controller in your non-functional board.

mkarcher wrote on Yesterday, 22:29:

If I understand you initial post correctly, the board died approximately at the moment you connected the keyboard. It sounds like you connected the keyboard while the system was powered on. This is an operation people tell you not to do, because there is no proper power sequencing (GND and +5V pins making connection before the data pins) on the AT keyboard connector. While I also did connect keyboards while a system was powered on without ill effects, the danger oftentimes quoted: "Connecting an AT keyboard or a PS/2 mouse with the system turned on will likely damage your system" possibly sometimes is real. The keyboard connects to the Intel 8042 auxilliary processor IBM introduced with the IBM AT, which is usually called "keyboard controller", but actually does some more auxilliary jobs controlling the AT platform, and is essential for a well-behaving system. It's possible that the issues you are facing now are due to a broken keyboard controller.

If you have another 286/386/486 board that does not have a PS/2 mouse port or a pin header for a PS/2 mouse port, try using the keyboard controller from that board instead of the keyboard controller in your non-functional board.

You're correct. The keyboard was connected afterward. I'll see if I can get another keyboard controller to test, but could some other component have been damaged? I wasn't aware of this problem, so it's a valuable learning experience.