G3 beige desktop strangeness

[billynomates]

Howdy all

I've got a ye olde G3 beige desktop, with a zip drive, 256MB RAM, 8GB disk, etc. OS X 10.2.8.

It will work correctly for about 30 mins - an hour, but will then turn off. Then, it won't power back on. Unless I wait (not sure how long, as I've always just put it back into storage when this happens). Eventually it will spring back into life, where it will work again for about 30 minutes...

I've just fitted a new PRAM battery, which appears to have made no difference!

Any ideas as to what could be wrong? Guessing power supply, but I'm not really a hardware sort of guy...

Cheers!

 

[Bunsen]

It might be overheating. The original thermal paste between the CPU and heatsink has almost certainly dried out, if it hasn't been renewed. Also check that the heatsink clip is the right way round - it's not symmetrical, and the lowest point has to be over the CPU die. While you're checking that, might as well redo the thermal paste. Searches here will reveal how to do it.

If you suspect the power supply, you can replace it with an ATX supply by changing the position of a jumper on the motherboard from "Mac" to "ATX"

 

[Unknown_K]

You can use ATX on a tower (will fit fine), but I don't think the desktop version can fit a standard ATX supply in the case.

 

[billynomates]

Thanks - turned out to be the thermal paste on the CPU.

Bought some. Applied it. And then it blew up!

So I'm consigning it to the great scrapyard in the sky xx(

 

[Osgeld]

how did you manage that :?:

 

[Mars478]

Lolwut? What do you mean it blew up? Pictures?

 

[Unknown_K]

Too much paste is worse then none at all, even a little that gets stuck on the cache leads will short out a chip.

 

[billynomates]

Well, the thing went BANG, and my house RCD tripped (at least it tested that...), a nice smell of burning electrics coming from the power supply followed...

This thing is toast, but have managed to salvage :

6MB video ram card

384MB RAM

G3 Desktop ROM

Weird, small PCB with inductors, coils and the like

If anyone could use any of this, let me know...

 

[Osgeld]

Too much paste is worse then none at all, even a little that gets stuck on the cache leads will short out a chip.

yea if your using lead paste, ive never seen thermal paste that had enough continuity to even be measured with normal tools

 

[Charlieman]

Well, the thing went BANG, and my house RCD tripped (at least it tested that...), a nice smell of burning electrics coming from the power supply followed...

The same thing has happened to me when recovering ye olde Mac. The intermittent shutdown was a clue to the problem, and the psu bang was the answer.

Had the G3 been stored in a loft or garage for a while? It just needed a few weeks indoors to thermally adjust and dry out.

Weird, small PCB with inductors, coils and the like

That's the voltage regulator for the cpu. A handy spare.
Are you 100% certain that the logic board is blown? I've seen quite a few psu bangs that have not killed the computer. In your case, you can test the logic board using a generic ATX psu (move the jumper on the logic board to PS/2).