Best is to unmount everything and start testing on a test bench. (there might be a short)

Swap items one by one till you find the culprit 😉

I meant it more like: does anyone know how to fix the power switch? I'm pretty sure that's where the problem is 😀
OR a way to the PSU on without using the power switch.

Sounds like an AT PSU... you'll have to fix the switch - an ATX PSU can be switched on via shorting two pins in the large multi-way plug, but this is not possible with the AT spec.

From the description it sounds like an AT PSU alright, which means that the cable (and the switch) carry mains power when plugged in. Do not try to fix this yourself if you don't know exactly what you are doing.

BTW, if the switch on an AT PSU is really broken, the PSU wouldn't turn on at all. The fact that it comes alive only for a short moment rather indicates that the problem is somewhere else.

megatron-uk wrote:

you'll have to fix the switch

^Yup

And frankly, I wouldn't try this myself. the AT PSU's are not really irreplaceable as there are ATX2AT adapters to be had for like €10 or so. Use one of those with a (very affordable) 250W ATX PSU of good manufacture

An ATX PSU and adapter cable is definitely the way to go if you don't know what you're doing..... as long as the Compaq takes a standard sized power supply - Compaq machines of that time are similar to the Dell machines of today!

Thanks for the replies so far. Frustrating that something seemingly so simple is beyond my powers to repair. Tried fiddling with it this afternoon and got zapped. No more of that 🙁
Too bad, because it is such a nice machine, with the Tseng ET4000/W32p on-board and an AMD 586 133 MHZ overdrive proc.

Are you absolutely sure it uses a non-standard PSU pinout?
And even if it does, that doesn't mean it's impossible to mod an ATX2AT adapter to fit it 😉

Edit:And be extremely careful when fiddling with the insides of any PSU!!! This includes the AT power switch, it could be hazardous both to your home and yourself!!!

No, i'm pretty sure it's standard (2x6 pins). I'm just not a big fan of modding vintage stuff like this 😢

But I guess i'll have to if I want to get this to work.

Sugoll wrote:

No, i'm pretty sure it's standard (2x6 pins). I'm just not a big fan of modding vintage stuff like this 😢

But I guess i'll have to if I want to get this to work.

You'd better!

133mhz overdrive chip. Woot!

And I second what 5u3 said. Take the power supply out of the machine entirely, place it on a non conductive surface (wood, tile, something), and plug it in. If the fan turns on in the power supply, your problem lies elsewhere. Also, make sure the switch is in the "on" position before you do this, and maybe plug the thing in from the wall socket side of the power supply rather than the power supply end if you're worried about getting shocked.