You're more likely to get responses if you include a photo of the board. People see that there is a photo, then find it worthy to read the text.

I am going through a similar situation with a motherboard right now. The symptoms are identical to yours, so far. I have started a post on eevblog and a lot of people came back with some really good troubleshooting suggestions, that are outside the norm. I highly recommend you take a look at this active post, http://www.eevblog.com/forum/repair/how-to-tr … n-oscilloscope/

Thanks, followed your advice and uploaded a photo of the board.
I've read the post on eevblog and will look there for further updates, however my lack of tools (not to mention skills and knowledge in this area) means that my chances are slim.
I don't have a 'scope or a identical board that works, and to further complicate things, the chipset is a rebrand of something else (UMC perhaps).
Can you hear a faint click in the speaker when shorting the Reset pins on your dead boards? Mine does that...

I haven't checked for that yet.

Even if it is a UMC rebrand, we don't have the UMC 8881/8886 chipsets.

One guy on eevblog was saying that this $6 poor-man's logic analyser for $6 could be of use, http://forum.hobbycomponents.com/viewtopic.php?f=102&t=1891

It's an ali finali board, the manual is here (see attachment). That board will post without a battery, you should just have removed it (by shaking it) before trying to boot. It should beep with only the cpu and the speaker, may be the jumper configuration is wrong.

Thanks,
I never booted with the reversed battery.
I have the manual, tried almost all jumper configurations with the 5x86, now I have an AMD DX4-100 installed and the jumpers are configured correctly for it.

feipoa wrote:

I haven't checked for that yet.

Even if it is a UMC rebrand, we don't have the UMC 8881/8886 chipsets.

One guy on eevblog was saying that this $6 poor-man's logic analyser for $6 could be of use, http://forum.hobbycomponents.com/viewtopic.php?f=102&t=1891

The chipset is ALi. I have an identical board (also dead) and the chips read "ALi M1489".

Sorry, I meant to write "chipset datasheets", not "chipsets". Doesn't matter anyway, though, as the chipset is ALi. But, we also don't have the datasheets for that ALi chipset either.

Today's update: inspired by feipoa's thread on eevblog I proceeded to check some things. Reset line to the CPU is ok, only going high for a moment at power-up or whenever I short the "reset" header on the motherboard. Clocks also seem ok, checked ISA/PCI/CPU clock pins with one of my multimeters that should be able to measure up to 40MHz (but actually doesn't; at 33MHz it shows zero, so at first I thought I had nailed the problem. But then I lowered the clock to 25MHz and it was able to measure it accurately. I also checked the PCI frequency at 1/2 divider and found it to be ok : 25MHz with board set to 50, down to 12.5 when the board was set for 25)

Hopefully you find something. I might need to slow down on that eevblog thread a bit. I'm not getting enough sleep.

feipoa wrote:

Doesn't matter anyway, though, as the chipset is ALi. But, we also don't have the datasheets for that ALi chipset either.

of course we do ;o) ALi M1489 was used as AMDs reference design for 486/586 processors
quicknick go ahead and make a thread on eevblog if you can get your hands on better equipment (friendly HAM operator, hackerspace) and have some ee knowledge already