Odd Problem With My G4 Mirror Door Mac

[2112st]

Hey folks!

So, to preface this-the machine is not used often. This is what happens once in a while....

I hit the power button, and nothing. I unplug and plug the power cord back into the G4, and it boots up. The clock settings are lost, and I have to reset them. FYI, the Saft PRAM battery I put in around 8 years ago. It's still in decent shape and holds a charge.

Any idea what this problem could be?

 

[ClassicHasClass]

Power supply. Very common on the MDDs.

 

[2112st]

Power supply. Very common on the MDDs.

So, the power supply is beginning its death spiral, eh? What could I replace it with?

 

[ClassicHasClass]

MDD power supplies aren't hard to find used and are generally straightforward swaps (here's me switching one out in mine a few years ago: https://oldvcr.blogspot.com/2020/10/refurb-weekend-power-mac-g4-mdd.html ), but you run the risk of getting one of the pre-recall units which will fail sooner. If you don't need the ADC voltage, there are projects to replace it with a standard ATX supply, as long as you don't mind the supply being external since I don't know of any ATX-compatible supply that will fit in the MDD. See http://atxg4.com/mdd.html for details on that.

And don't forget to replace the PRAM battery while you're there since that seems to have died too.

 

[2112st]

MDD power supplies aren't hard to find used and are generally straightforward swaps (here's me switching one out in mine a few years ago: https://oldvcr.blogspot.com/2020/10/refurb-weekend-power-mac-g4-mdd.html ), but you run the risk of getting one of the pre-recall units which will fail sooner. If you don't need the ADC voltage, there are projects to replace it with a standard ATX supply, as long as you don't mind the supply being external since I don't know of any ATX-compatible supply that will fit in the MDD. See http://atxg4.com/mdd.html for details on that.

And don't forget to replace the PRAM battery while you're there since that seems to have died too.

Just out of curiosity-and not that I'd do it myself since I'm not an electronics whiz-is this because the capacitors inside the old PS are going bad? If so, would it benefit from a recap?

 

[ClassicHasClass]

You could try, and I don't discount they may make things worse, but MDD power supplies were problematic even when they were new and were the subject of a recall. My dual 1.25 was the first computer I ever bought new and was affected by it, and Apple sent me a new one.

 

[2112st]

Hmmm. I now recall Action Retro (Sean) having to do a PS swap in one of his videos. I'll have to dig it up. This G4's current use is as a file server.

 

[2112st]

ClassicHasClass-clarifying my last post...Sean replaced the power supply with something other than the one that was made for the MDD. I'll need to dig that video up to see what he used.

 

[2112st]

Sean talks about it here at 12:15.

 

[phunguss]

I just picked up an ailing MDD with power problem... I have a ATX FLEX 600W psu I will try to fit in, much smaller than the original PSU, so it should fit internally.

 

[2112st]

I just picked up an ailing MDD with power problem... I have a ATX FLEX 600W psu I will try to fit in, much smaller than the original PSU, so it should fit internally.

I plan to order the set-up that Sean talks about here. While I'll also order a new PRAM battery, it's odd that the old one didn't work, since I tested it and it still holds a charge. Again-I put it in myself around 8 years ago. Eh, whatever. I'll just get another one.

 

[2112st]

Okay-power supply, MDD ATX adapter cable & Saft batteries ordered. I cringed a little at the total price, but since I don't do this sort of thing often and because I want to continue using this G4 MDD (data storage as well as eventually playing around with an additional operating system), I went for it. This should be interesting.

 

[phunguss]

I found a PSU slave cable, from my days of crypto-mining, no longer needed, so I will re-pin it into my own ATX adapter. I have these automotive plug-pin removers, so I just need to figure out which one works best. And I will use some colored electrical tape to keep me sane.

Here is my 600W PSU, it has 2 molex, 4 sata power, and dual 8-pin for GPU.

 

[phunguss]

Finished my cable, I didn't have orange tape for the 3.3v, so I used white since the white wire will not be used.

The motherboard 8pin (2 x 4pin) connector supplies two extra 12v and one ground.

So, at least my MDD powers on, where it did not before. Light will come on, then fans go high, no chime, no video. Reseated CPU, tried single DIMM in various slots, same results. Google-Fu tells me I need to supply that 28V line for the video card... so ordered one of these on the cheap.

 

[S. Pupp]

The 28V line is only needed if you are using an ADC monitor.

 

[2112st]

My new power supply and replacement PRAM batteries should arrive today; the ATX cable adapter later this week or next week.