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Power Mac G4 MDD (2002) - From a Kernel Panic galore (!) to power supply troubles (sigh)

Alexis Trinquet

Alexis Trinquet

macrumors regular
Original poster
Mar 1, 2020
168
177
Gouvieux, France
Hey there! I'm posting this here as I'm completely out of ideas... Just in case somebody has any pointers or ran into a similar issue, I'm all ears.

What I currently have is a Power Mac G4 MDD (2002, dually 1 GHz) that I've been trying to slowly trying to restore.. So far so good, it used to boot up on first try.

But, since a few days, it more often than not either completely locks up at boot (either showing "still waiting for root device" endlessly), or gets stuck around this stage:
17009364308716693789238869582544.jpg

And now it's gotten worse, it hands out kernel panics like free candy, every time it's a different error message:
17009889194633481522774743102443.jpg
received_308723128786339.jpeg
17009894178751924600933152441363.jpg
17009906850108810686654164351423.jpg

I tried reseating the RAM modules, this did help somewhat, as in, I could boot once, but then it started becoming unstable again.

I took off the CPU card to repaste the CPUs before I ever tried to power it up... Maybe on the off chance that I bent some pins.

I'm gonna see if I can burn a ASD disk, I found a IDE DVD drive in my parts bin.. AHT didn't report any faults whatsoever (tried to do five rounds of extended testing, still nothing)

Kind regards,
Alexis
 
Hmm, it seems to point to your hdd as the ASD disk booted and ran fine from the CD-ROM. Here are some things to check (not necessarily in this order).

Since you repasted the d card, check to see if a pin bent or if there is a piece of lint/debris stuck and reseat it.
Try a different pata cable to rule out a wonky donky cable.
Remove all but one stick of known good ram.
Reset PRAM
Run firstaid in DU from a boot disk inserted into your CD-ROM.
Try yet another HDD with fresh OSX install.
 
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I'm trying to get it to boot, but now it's throwing this error (pardon my awful photography skills):
17011207027735381134352905417140.jpg

This is with a new IDE cable and just a DVD drive attached (trying to boot off a 10.4 disk I just burned), only one stick of RAM fitted (PC-2700 DDR1 256MB).

I don't get it, it booted fine for a week or two, then it suddenly degraded like that all out of the blue.

Edit:
Since you repasted the d card, check to see if there is a pin bent [...]
Click to expand...
I'm glad you suggested that because I just popped off the heatsink and the CPU card, and there was one pin slightly bent out of shape that I was able to bend back, and there was a tiny plastic debris that had gotten lodged onto the logic board socket.

The thermal paste on the CPUs looked like a chunk of it had evaporated.. Should I just put a thermal pad and call it done? Or is there is any way I can counter that weird phenomenon?
 
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That is odd. If that is the case, I suspect the drive. Even replacements fail. I’ve got a few that have bit the dust with bad sectors as well and are unreliable.
 
Yeah I'm starting to think that the hard drive also is suspicious, as I saw it would hang on a extension related to ATA (KeyLargoATA) a couple of times or throw a kernel panic right after it loaded.

I've got another PC old enough to have IDE ports, so if I can find a HDD stress test program, I'll run it on the drives to see how they hold up.
 
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Congratulations on working through the problem and figuring it out! Now you have a functioning MDD that was otherwise on its way to ewaste - very cool. I assume that old pc runs some flavor of windows (I have an old win pc on my bench as well). I recommend DiskCheckup & HDDScan. Both are win apps but are very handy for looking at and diagnosing wonky drive behavior & health.

Don’t forget about chkdsk as well which is built into your windows. Good luck
 
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I spoke too soon, now I can't get it to start at all again, now whenever I press the power button it just lights up then fades down. I guess this G4 really wants to put up a fight :confused:

Still, I'm gonna run MHDD (which HDDScan is based on) on my old PC, since it has a IDE port on the motherboard, that's exactly what I need.
 
Hmm, now that on/off behavior sounds like a PSU issue which is not unexpected at all. MDD psus are notoriously flaky. I saw a YT vid where ActionRetro Sean retro fitted an ATX psu into his MDD with the help of an adapter. It was very cool and what I will try if & when my MDD psu bites the big one. If your psu is jerking you around, this is a path forward to fix it with a new psu, not a just-as-old, over priced replacement.

Good luck.
 
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Yeah, I heard a loud click coming from it when it shut down. I'm gonna try recapping it, I've got nothing to lose on that, I already have a LC II PSU that needs new caps, I'll throw in an order for both. Might as well kill two birds with one stone.

At least I know that the logic board isn't dead, there's the silver lining :)
 
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I don't at the moment, I'm searching around for new caps and everywhere the prices differ, currently evaluating my options.

The only part where I'm a bit stuck is which caps should be replaced by low-ESR ones, that is something I never could wrap my head around.
 
Certificate of Excellence said:
Seriously great silver lining. A recap is more cost effective than sourcing another logic board I’d think. Do you have an estimate on the cost of the recap components?
Click to expand...
Okay, so on mouser at least, that'd run me 30 euros or so (shipping included, of course, without shipping and taxes I'd be out 12-13 euros), which compared to spending 'round ~150 euros for getting it sent over the pond to ACX electronics' mail-in PSU repair service, is more reasonable.

I'm gonna do my research so I don't screw this up, and while doing so, I found some (not-so-reassuring) threads mentioning that the Samsung PSUs had two failure modes:

The first one (the "explosive" failure): where some components on the primary side literally catching fire (most notably, the thermistor on the primary input burning up), that one I'm not sure what causes it, some folks point out that it's due to a cascading failure kick-started by a capacitor failing.

The second one (what I call the "non-starter" failure), where the power button glows when held in but slowly dims out when released.. This is the failure mode that mine seems to be suffering from, there is a lengthy thread on the BadCaps forum (I don't know if I can put a link to it. Can I?) discussing it. Of interest, a post in particular caught my attention:

1701255301102.png


Since I don't have an ESR tester, I'm gonna replace all the caps in one go, I know this probably isn't the best approach, but since I've never tackled a SMPSU (and knowing how some Macs are notorious for bad caps) I don't want to take any chances.

It's tough finding info about the Samsung PSUs, whereas there's a LOT of posts regarding the AcBel PSUs). I've tore mine apart, compared to the AcBel it's a bit easier (the IEC connector isn't directly hardwired on the board for instance, and the fans have connectors) though it has those two daughter-boards that are soldered in using pin headers.

-Alexis
 
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Alexis Trinquet said:
Okay, so on mouser at least, that'd run me 30 euros or so (shipping included, of course, without shipping and taxes I'd be out 12-13 euros), which compared to spending 'round ~150 euros for getting it sent over the pond to ACX electronics' mail-in PSU repair service, is more reasonable.

I'm gonna do my research so I don't screw this up, and while doing so, I found some (not-so-reassuring) threads mentioning that the Samsung PSUs had two failure modes:

The first one (the "explosive" failure): where some components on the primary side literally catching fire (most notably, the thermistor on the primary input burning up), that one I'm not sure what causes it, some folks point out that it's due to a cascading failure kick-started by a capacitor failing.

The second one (what I call the "non-starter" failure), where the power button glows when held in but slowly dims out when released.. This is the failure mode that mine seems to be suffering from, there is a lengthy thread on the BadCaps forum (I don't know if I can put a link to it. Can I?) discussing it. Of interest, a post in particular caught my attention:

View attachment 2318675

Since I don't have an ESR tester, I'm gonna replace all the caps in one go, I know this probably isn't the best approach, but since I've never tackled a SMPSU (and knowing how some Macs are notorious for bad caps) I don't want to take any chances.

It's tough finding info about the Samsung PSUs, whereas there's a LOT of posts regarding the AcBel PSUs). I've tore mine apart, compared to the AcBel it's a bit easier (the IEC connector isn't directly hardwired on the board for instance, and the fans have connectors) though it has those two daughter-boards that are soldered in using pin headers.

-Alexis
Click to expand...
I’ve had a couple MDD psus fail on me over the years here in the States which were all Acbels, so I’ve never seen a Samsung psu. I had assumed all MDD psus were Acbels lol. Learned something today :)
 
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Well, I have a couple of good news and bad news.

The good news is that A) the Samsung PSUs are indeed easier to take apart compared to the AcBels (see picture one, there's headers everywhere), and B) if needed you just need to undo a couple of screws and the whole PCB goes out of its sled.

The bad news, my PSU seems to also have blown its thermistor :(

It must've failed ages ago as I don't remember seeing it spew flames or make any funny noises (besides a tiny click)
 

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Another thing I noticed is that on the few pictures of a Samsung PSU that I could find, they all had a big CapXon capacitor whereas on mine it's a Würth Elektronik cap. Perhaps mine had been serviced at some point??

There's defo some tiny CapXons hiding in the PSU's daughterboards, they don't look bad but you never know.. (if only I had a ESR meter!) the big scary Würth cap is gonna stay (I'll still order a replacement, just in case).

----
Re: The hard drive
@Tratkazir_the_1st - Don't worry about the hard drives :) I've got plenty of utilities for that, first I'll check them using CrystalDiskInfo then I'll hit them with a couple of rounds from MHDD/Victoria (loop scan+erase), in any case I'm going to eventually put SATA SSDs in my MDD, I'll just keep the IDE drives for non-critical data storage.
 
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Tratkazir_the_1st said:
What are you planning to use for this? I mean which SATA card? (I'm personally prefer SAS from LSI, but seeking for PCI64 card was unsuccessful). It's hard to find something this type in second-hand market here in Russia.
Click to expand...
I'm gonna use Startech adapters, until I can find a Seritek PCI-64 SATA HBA. Even where I live (rural France) finding one is easier said than done :(

If not, I'll just find one of those Silicon Image cards and flash it manually, those on the other hand I can find a few for relatively cheap
 
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