By big trace you're referring to the one coming from the PSU?

Did you check the four small traces that ran under the battery and resistor that's next to the keyboard DIN?

For the battery, that's a four pin header down the board labeled battery. You can get one of the four AA battery enclosure the terminates to a four connector female Jack.

SScorpio wrote on 2020-10-25, 04:25:

By big trace you're referring to the one coming from the PSU?

Did you check the four small traces that ran under the battery and resistor that's next to the keyboard DIN?

For the battery, that's a four pin header down the board labeled battery. You can get one of the four AA battery enclosure the terminates to a four connector female Jack.

Thanks for the reply. Yep the one from the PSU has been patched on the back.

I haven't done the small 4 yet, I need to remove the KB connector as I'm not sure where they go, but thanks sounds like the next job.

Yes I was planning on using the external battery connector but is 4xAA too high a voltage?

Maybe @pshipkov from this thread 3 (+3 more) retro battle stations could give some help (same board)

Does setting the turbo jumper change the weak beep?
What components did you use when testing the board?
Can you try and measure the voltages with the PSU connected to the board?

PC Hoarder Patrol wrote on 2020-10-25, 05:01:

Maybe @pshipkov from this thread 3 (+3 more) retro battle stations could give some help (same board)

Great thank you. I will check in with pshipkov. But yes looks like the same board (except mine is SIPP mem). Thanks!

Doornkaat wrote on 2020-10-25, 07:15:

Does setting the turbo jumper change the weak beep?
What components did you use when testing the board?
Can you try and measure the voltages with the PSU connected to the board?

Thanks I haven't tried with a turbo button attached.

So far I have just tried with with and without a VGA card, a WD90C00. It same with the motherboard and I have tested on another machine and it works well.

I also have not tested voltages, another good idea thanks!

I wish you luck getting it repaired. That VLSI chipset is very fast and supports shadow RAM

mwdmeyer wrote on 2020-10-25, 04:31:

Thanks for the reply. Yep the one from the PSU has been patched on the back. […]
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SScorpio wrote on 2020-10-25, 04:25:

By big trace you're referring to the one coming from the PSU?

Did you check the four small traces that ran under the battery and resistor that's next to the keyboard DIN?

For the battery, that's a four pin header down the board labeled battery. You can get one of the four AA battery enclosure the terminates to a four connector female Jack.

Thanks for the reply. Yep the one from the PSU has been patched on the back.

I haven't done the small 4 yet, I need to remove the KB connector as I'm not sure where they go, but thanks sounds like the next job.

Yes I was planning on using the external battery connector but is 4xAA too high a voltage?

Remove the KB connector and access the damage before doing anything else.

Viewing the photo on a larger screen, the via to the bottom left of capacitor C21 looks like it may also be corroded. Finally, I also see some odd discoloration below the notch for the BIOS chip. It may just be dirt/dust. But battery acid can spread to odd places and get under chips and sockets and wreck all kinds of havoc.

If that's actually a picture of your board, it doesn't look too good. There seems to be a widespread corrosion, apart from the one caused by the battery. It can be seen on the traces between the ISA slots all the way to the chipset and NPU socket. Maybe soldermask was improperly applied, or storage conditions were poor.

Thank you guys for all your help.

Yes it is possible there is more issues with this board than is fixable (e.g traces between the ISA slots) but I haven't given up yet.

I probably won't get any time until next weekend to work on it further (and maybe not even then) but I will measure voltages, remove KB connector and provide some updated photos after the cleaning I did.

I really want to get a working 286 going and I've got the perfect ET4000AX to go with it, so I will continue on trying!

I did a couple of quick tests.

PSU is outputting 12v/5v correctly when connected to the motherboard. I'm not sure if there are some points on the board I can test.

When I bridge the turbo switch I do get a different (worse/couple of squeaks) response but not improved.

I'm still waiting on the POST board which should at least tell me the voltages on the ISA ports.

I think I need some better tools to repair this than what I have, maybe I need to find an electronics group in Sydney who can help!

Well I got the post card. Seems like it isn't even able to read the BIOS.

It does at least show the 12/5v rails are working correctly to the ISA slots. I've tested a few of the ISA slots all with the same output.

If you already removed the keyboard connector and checked and repaired all the visible damaged traces. You'll likely need to remove the BIOS socket and the socket between it and the first ISA slot. From there check each trace. The acid could easily have eaten some traces under those.

A simple continuity check on the first 8-bit slot could help.
As SSorpio suggests maybe you have broken trace affecting all. Could be data, address...

mwdmeyer wrote on 2020-10-25, 04:06:

Hi All, […]
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Hi All,

I have this 286 motherboard I am trying to repair.

It has some battery corrosion but I believe it is repariable.

Here is a photo:

https://www.vogonswiki.com/images/e/eb/286_Motherboard.jpeg

I'm having trouble finding any information about this motherboard which is making repairs difficult.

At this stage I have removed the battery and connected a replacement wire on the back to repair the ISA/large trace that is corroded (although it did still have continuity).

Currently when I switch it on either I get a faint beep (or sometimes a very distorted beep). If I switch on/off the PSU quickly I have been able to get one long continuous beep (which someone sounds like a capacitor issue).

I have an ISA POST card on order and I need to find a replacement CMOS battery.

Any suggestions would be fantasic.

I stumbled across your board as I've actually got a similar one 😀
Mines POST but I was trying to find jumper/info on the shadow RAM
I'll attach my pic here for comparison in the hope it helps you somehow..

4xtx wrote on 2021-04-01, 12:07:

I stumbled across your board as I've actually got a similar one 😀
Mines POST but I was trying to find jumper/info on the shadow RAM
I'll attach my pic here for comparison in the hope it helps you somehow..

Shadow ram tends to be set in the bios.