Your PSU refuses to start because there's a short in the board. Very likely at least one of the tantalum caps has failed short.

You will need a multimeter (and possibly desoldering the tantalums) to properly determine what is causing the short.

ok cool so with the multimeter am i checking for continuity or voltage?

You can start by checking for continuity between the pins of the power connector: the 4 middle ones are GND, so if there is continuity between those and one or more of the outer pins then you have a short.

Make sure to remove CPU and other cards, do your testing on the bare motherboard without anything connected to it.

ok so if i unplug the psu and check the 4 GND pins with the others there is only connectivity from all the grounds to one of the outside pins. I can't see any visual damage on the board though.

What color is the wire from the PSU that connects to the pin that is shorted to ground? Red is +5V, yellow is +12V, white is -5V, blue is -12V and orange is PG.

Next, you can check for continuity between the two legs of each tantalum capacitor in the back of the board. I have marked the tantalums I can see in your picture:

If any of those are shorted, you've probably found the problem (though you really need to pull them off to determine which tantalums need replacing since they may be connected in parallel).

It's blue, only one of them has continuity on both legs. I'm guessing that's the gremlin? It's the third one from the left directly under the power connector.

Can I just say I really appreciate your help.

Yeah, that sounds about right, tantalums on the -12V line (blue wire) are usually the first ones to pop.

If you have a soldering iron, you can remove that shorted cap and try again, that cap should not be critical for the board to work. If that fixes the problem, then you can replace it with a new one.

A word of warning though: please check the PSU with a dummy load (such as a dead hard drive) before connecting it again to the board. The voltages on all the power rails should be within spec, especially -12V... I suspect that a voltage spike in the -12V line is what may have killed that tantalum. All of this is assuming that PSU is the one that came with the board.

PSU is not original as it's from parts that i'm putting together. I had some parts from my original 486 and am adding the rest.

I will desolder and replace it and let you know how it goes.

Bam! she posts.

thanks again for your help.

Cool! Glad you were able to fix it, it's a nice board.