Power PC G3 Desktop completely dead

[bancquo]

Just joined, and first post from a cold and wet Scotland... ?️
In the dim and distant past, our company was taken over, and we were forced onto PCs.
At the time we had the option to buy our Macs, which I did, and it's been lying there unused until now, when I was supposed to be starting my retirement project of hooking up all my old hard drives, and recovering all my old photos.
Of course, it hasn't gone like that...
Instead of the welcoming 'boing' I have a machine that's completely dead: no sign of life at all.
I tried fitting a new 3.6V battery, in case it was related to that (I didn't think so, but it was cheap enough to try), and of course it made no difference.
Question is, what sort of thing can go wrong to give this problem when the Mac's been lying doing nothing, and is there anything I can do to try and bring it back to life myself?
I can handle a screwdriver and a voltmeter, but electronics are completely beyond me...
Any tips of things I can try to bring it back to life would be very welcome.
Is there anything I can do to check the output from the power supply?
Do the start buttons fail?
Look forward to any helpful suggestions, and thanks in advance

 

[eyoungren]

Just joined, and first post from a cold and wet Scotland... ?️
In the dim and distant past, our company was taken over, and we were forced onto PCs.
At the time we had the option to buy our Macs, which I did, and it's been lying there unused until now, when I was supposed to be starting my retirement project of hooking up all my old hard drives, and recovering all my old photos.
Of course, it hasn't gone like that...
Instead of the welcoming 'boing' I have a machine that's completely dead: no sign of life at all.
I tried fitting a new 3.6V battery, in case it was related to that (I didn't think so, but it was cheap enough to try), and of course it made no difference.
Question is, what sort of thing can go wrong to give this problem when the Mac's been lying doing nothing, and is there anything I can do to try and bring it back to life myself?
I can handle a screwdriver and a voltmeter, but electronics are completely beyond me...
Any tips of things I can try to bring it back to life would be very welcome.
Is there anything I can do to check the output from the power supply?
Do the start buttons fail?
Look forward to any helpful suggestions, and thanks in advance

Some of the Classic Macs and the iMac G5 series were known for failing capacitors. I have no idea if this might be the case here, but I'd look inside the PSU to see if any have gone bad.

I am absolutely no electronics expert but bad caps are pretty easy to spot. These are those plastic knob looking devices that sit above electronic boards. A bad one either bulges or the top opens up and leaks out capacitor fluid. It's very obvious.

If you see any in the PSU then you'll probably need to replace that - unless you know someone who can replace caps for you.

 

[mustagcoupe]

Remove and reseat the memory and expansion cards, sometimes stuff isnt making good contact and that helps. If still nothing disconnect all the drive power and data cables and remove all but one of the memory sticks, if still nothing swap the one remaining memory stick for a different one. If it still wont boot maybe the power supply died.

EDIT: It is possible for the power switch to fail in a humid location. I had that happen to me on a laptop. To rule that out try using the power button on the keyboard if it has one or shorting the pins on the switch with a wire.

 

[bancquo]

Some of the Classic Macs and the iMac G5 series were known for failing capacitors. I have no idea if this might be the case here, but I'd look inside the PSU to see if any have gone bad.

I am absolutely no electronics expert but bad caps are pretty easy to spot. These are those plastic knob looking devices that sit above electronic boards. A bad one either bulges or the top opens up and leaks out capacitor fluid. It's very obvious.

If you see any in the PSU then you'll probably need to replace that - unless you know someone who can replace caps for you.

Thanks: good starting point

 

[bancquo]

Remove and reseat the memory and expansion cards, sometimes stuff isnt making good contact and that helps. If still nothing disconnect all the drive power and data cables and remove all but one of the memory sticks, if still nothing swap the one remaining memory stick for a different one. If it still wont boot maybe the power supply died.

Thanks. Is the PRAM battery the one I replaced already? SAFT 3.6V Lithium...

 

[eyoungren]

Thanks. Is the PRAM battery the one I replaced already? SAFT 3.6V Lithium...

Yes, that's the PRAM battery.

 

[mustagcoupe]

Thanks. Is the PRAM battery the one I replaced already? SAFT 3.6V Lithium...

Yeah. I removed that in my edit because i saw you already replaced it. I didnt read carefully enough the first time. Check the battery with a multimeter to make sure its actually good, its possible to get a defective one. It should also boot with the battery totally removed if you want to try that and see if it does anything. Im not sure if the beige g3 has a pmu reset button. Look for a button labled pmu on the motherboard and if it has one press it once and only once. Do not hold it down or press it twice or you could corrupt the power management unit.

 

[bancquo]

Yeah. I removed that in my edit because i saw you already replaced it. I didnt read carefully enough the first time. Check the battery with a multimeter to make sure its actually good, its possible to get a defective one. It should also boot with the battery totally removed if you want to try that and see if it does anything. Im not sure if the beige g3 has a pmu reset button. Look for a button labled pmu on the motherboard and if it has one press it once and only once. Do not hold it down or press it twice or you could corrupt the power management unit.

Thanks for that: I'll get the magnifying glass out tomorrow! Power cord connected when I do that, or not?

 

[mustagcoupe]

I found a diagram for that logic board. The button is labeled cuda but the same instructions still apply. Press once and only once, dont hold it or press twice. Did you try the power button on the keyboard. Im assuming you have the proper ADB keyboard for it. It should have a power button somewhere on it that will probably be labeled with a weird triangle.

 

[bancquo]

I found a diagram for that logic board. The button is labeled cuda but the same instructions still apply. Press once and only once, dont hold it or press twice. Did you try the power button on the keyboard. Im assuming you have the proper ADB keyboard for it. It should have a power button somewhere on it that will probably be labeled with a weird triangle.

View attachment 1967545

Great: now I know what to look for. The keyboard I have in doesn't have a power button, but I have a box of them somewhere, so I'll try and pull them out in the morning, and see what we have. Watch this space. Appreciate the help.

 

[mustagcoupe]

Great: now I know what to look for. The keyboard I have in doesn't have a power button, but I have a box of them somewhere, so I'll try and pull them out in the morning, and see what we have. Watch this space. Appreciate the help.

Are you sure it doesnt. Most ADB keyboards did. Sometimes it doesnt look like a power button. I attached a picture with one style of power button circled. Yours might not be the same but i think they were all labeled with that triangle symbol.

 

[onre]

I am absolutely no electronics expert but bad caps are pretty easy to spot. These are those plastic knob looking devices that sit above electronic boards. A bad one either bulges or the top opens up and leaks out capacitor fluid. It's very obvious.

If you see any in the PSU then you'll probably need to replace that - unless you know someone who can replace caps for you.

Solid advice. I'd like to add that a capacitor does not need to show any external symptoms to have gone bad. I replaced almost every cap inside my G5 PSU to get it going reliably again. A couple had very minor leakage under them but most looked absolutely fine. However, a tester revealed that almost all of them were gone.

 

[bancquo]

Are you sure it doesnt. Most ADB keyboards did. Sometimes it doesnt look like a power button. I attached a picture with one style of power button circled. Yours might not be the same but i think they were all labeled with that triangle symbol.
View attachment 1967547

Yes, you're right. It does have one, but not along the top where I was expecting it. No joy though, but thanks for the tip

 

[bancquo]

Just an update for all those helpful replies.
Got nowhere with anything, but a friend who's an electrical engineer volunteered to have a look, on the 'we've got nothing to lose' principle. He wasn't able to do anything with the power supply, but got some info on line about adapting a PC supply to suit.
"The power supply had none of the obvious faults and the area I think has the problem, is full of unidentified components and the internet provided no circuit diagrams. So instead, I found online how to make the Mac work with an ATX PC power supply and have bodged one in, as ATX is a different size. It looks horrendous but does seem to work, so you should be able to use it and then see and hopefully extract anything you want"

Hopefully on the home straight now!



Again, thanks for all the help.