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G4 MDD not booting

mmu_man

Well-known member
I was just given a G4 MDD which "stopped working suddenly".
When removing the PRAM battery I had the feeling it actually was in the wrong polarity, but I'm not entirely sure.

Fans spin, the power LED lights up, but that's it.
I've tried:
- reseating the RAM, the CPU…
- disconnecting unessential things (I noticed the optical drives IDE cable had wires cut).
- resetting PMU.

One very odd thing is, when I remove all the RAM, it does give a single beep, telling it doesn't find it. But when I put it back in, and I tried many combinations, it just sits here, not doing any sound.

I noticed the thermal paste was quite tried off, maybe one of the CPUs partially burnt and fails to execute code. I don't have spare a CPU board to try at the moment though.

Also, the logic board has some wires and SMD transistors soldered on, apparently to control one of the fans, and it also has two large resistors bridging some pins on the power supply connector on the bottom side, probably to force some load on the power supply… Some photos on twitter.

Anything I could try?
 

trag

Well-known member
A quick look at Ebay finds this CPU card ships internationally and is not too pricey. Although shipping will cost a bit. The seller has three of them and charges only slightly more to ship the 2nd and 3rd, so if you know anyone else in France who needs a MDD CPU card you could gang together.


I don't know if that is the problem with your machine, but it sounds like you're at the point where you need to swap parts.
 

mmu_man

Well-known member
"does not ship to France"… oh well.
LOL : "Ships worldwide" + "Excludes: [165 country names]" (yes, I did count them with CLI tools :p)
 

MOS8_030

Well-known member
Although it sounds like someone has done some work on this system I would suspect the power supply has failed or is failing.
This is a pretty common failure mode with these systems.
I would verify that the PS is working or not before swapping any other parts.
I replaced two OEM power supplies on my MDD system before I finally installed an ATX power supply.
It's a pretty simple procedure.
 

mmu_man

Well-known member
Ah yeah I forgot to mention I did verify all the voltages from the PSU as well as per this doc. But maybe it's still weak, at least I do have ATX PSUs handy.
 
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mmu_man

Well-known member
Just tried, didn't work any better. In fact it doesn't even beep for no RAM, just sits there, and after 10s it maxes out the fan as it'd do after a PMU reset.
Putting back the original PSU gives the original behavior again.
I didn't have all wires available, I only had one for 12V, but I doubt the RAM needs 12V.
 

NickNick

Well-known member
Have you tried a different ram simm? I'm working on a G3 which had ram and gave a bong but would not boot. Turned out it was bad ram causing the system to not boot. Try replacing the ram with a good stick.
 

mmu_man

Well-known member
Have you tried a different ram simm? I'm working on a G3 which had ram and gave a bong but would not boot. Turned out it was bad ram causing the system to not boot. Try replacing the ram with a good stick.
I already tried various combinations, and I just did again with two more PC2700 sticks I had around, nothing worked.
 
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