PowerMac G4 MDD Starting glitches

benvw99

macrumors member
Original poster
Apr 29, 2014
41
0
Selby, SD
hey everyone - haven't been on in a while. I am staying at my grandparents, and I have about 7 or 8 Powermac G4 mirror drive computers. All of them have the same problem - their startup.

so I plugged them in. Most of them powered on fine, but one didnt. It would start up, and within about 5 minutes of use, it would fall asleep. I was using it the whole time, so it wasnt on a timer or anything. I hit the power button to start it back up, and it came back on. after about 30 seconds, It would fall asleep again. I would power it up AGAIN, but it still shut off after 30 seconds. Any ideas?

Now for the main problem. Most of the computers start up fine and can be used normally. But once you shut them down, they cant be powered back on. I have found that the only way to do this is to unplug the power cord from the back of the computer. Then plug it back in and hit the power button. It comes right back on and is ready to use. Any ideas?

Thanks for you help.
 

bunnspecial

macrumors 604
May 3, 2014
7,146
4,167
Kentucky
I have an MDD that will act as the ones ones you're describing-i.e. it starts perfectly, but after shutting down requires being unplugged and plugged back in.

I've been told that it's a sign of a PSU on its way out-the MDD PSUs are notoriously unreliable. I've kept this one in place, as it's at least working and don't feel like dropping $70 on an infrequently used computer. I recently bought 5 in one lot, and only got one working PSU out of the bunch. I have two others that were bought before the lot, and one required a PSU replacement to work correctly(despite the fact that the previous owner said it had been working daily up until he was preparing it to ship to me).

I suspect that your other problem may be PSU related, although it could possibly be related to a power button going bad. If you have an ADC display by which you can power up the computer, you might try completely disconnecting the power button from the logic board. Otherwise, you might try disabling "sleep on pressing power button" under the Energy Saver control panel. I had a DA G4 that would do this, and it ultimately required PSU replacement, but doing the above should rule out one potential failure point.
 

bunnspecial

macrumors 604
May 3, 2014
7,146
4,167
Kentucky
You can rebuild the PSU if you have the skills with a soldering iron.
Do you know of an online guide or anything else that gives advice on this? I'd like to try it with one, but have never run across anything obvious in the ones I've opened up and haven't bothered tracing the circuit with a VOM or scope(maybe if I get a few snow days this winter I can take the time to sit down and do that).

I've also searched for troubleshooting guides or rebuild guides, but have never run across one.

As I said, I have a scope and am not too bad at soldering so feel like it's something I could do if I just had some guidance on what to look at.
 

Altemose

macrumors G3
Mar 26, 2013
9,171
479
Elkton, Maryland
I've also searched for troubleshooting guides or rebuild guides, but have never run across one.

As I said, I have a scope and am not too bad at soldering so feel like it's something I could do if I just had some guidance on what to look at.
I do not know of any guides. From what I have seen is that it simply is blown capacitors. You can order new capacitors on eBay and just desolder and replace the old ones. Since the MDD has a standard 24 pin ATX power port on the Logic Board you can use an ATX PSU. There is some information here and here.
 

benvw99

macrumors member
Original poster
Apr 29, 2014
41
0
Selby, SD
Sorry for double post...

I plugged in all 7 of the Powermac G4's and only ONE actually powered on somewhat. It will turn on fine, and run fine, but after I shut it off, it won't turn back on unless I unplug the power cord, as i said earlier. Oh well, looks like 6 of them are going to the dump.

One of them actually came with a CD and DVD burner, so I took it out and put it into the one working PM. Little bonus for me I guess. I also took out a whole load of RAM sticks, and put the biggest ones into the one working PM. So it would have been a pretty loaded computer, if it worked properly.

Is it possible to sell 6 donor PM's for $50 for all? or would $30 each be a more suitable route considering that they are semi-powerful?
 

DZ/015

macrumors 6502a
Mar 23, 2003
875
21
New England
You could also gut the power supply and install a micro atx ps inside the old case. They fit.

A little drilling and it works just fine. Quieter as well.
 

128keaton

macrumors 68020
Jan 13, 2013
2,029
413
Sorry for double post...

I plugged in all 7 of the Powermac G4's and only ONE actually powered on somewhat. It will turn on fine, and run fine, but after I shut it off, it won't turn back on unless I unplug the power cord, as i said earlier. Oh well, looks like 6 of them are going to the dump.

One of them actually came with a CD and DVD burner, so I took it out and put it into the one working PM. Little bonus for me I guess. I also took out a whole load of RAM sticks, and put the biggest ones into the one working PM. So it would have been a pretty loaded computer, if it worked properly.

Is it possible to sell 6 donor PM's for $50 for all? or would $30 each be a more suitable route considering that they are semi-powerful?
Never to the dump. I'd take them to your pawn shop or thrift store (or even the GOODWILL!)
 

benvw99

macrumors member
Original poster
Apr 29, 2014
41
0
Selby, SD
You could also gut the power supply and install a micro atx ps inside the old case. They fit.

A little drilling and it works just fine. Quieter as well.
How much will that cost though? I don't want to spend over $20 on each unit.

Never to the dump. I'd take them to your pawn shop or thrift store (or even the GOODWILL!)
I don't know how those really work - is it just donating or do they give me money for them?
 
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