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Power Mac G4 Won't Power Up

Z

z970

macrumors 68040
Original poster
Jun 2, 2017
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Hi all, I recently saved a Power Mac G4 QuickSilver from certain death at the local recycling center (always wanted one of these), and it came without a hard drive, memory, or a PRAM battery. Trouble is, it won't turn on. I tried multiple power cords w/ multiple power jacks, pressed the PMU reset button, and reseated the PSU molex connectors, all to no avail.

I voltage-tested the pins in the PSU's molex connectors, and I did get several readings up to a couple hundred volts. I did not get this result most of the time (though I probably wasn't doing it right). This makes the suggestion that the PSU should be OK, as it seems evident that the logic board appears to be receiving power.

It has an old electronic smell. Nothing close to burning, or suggestive of something previously being fried. The logic board looks fine, nothing seeming to be amiss.

So how often do the QS power buttons fail, likewise their logic boards? And what else can be done?

Thanks, all. Much appreciated. :)
 
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z970mp said:
Hi all, I recently saved a Power Mac G4 QuickSilver from certain death at the local recycling center (always wanted one of these), and it came without a hard drive, memory, or a PRAM battery. Trouble is, it won't turn on. I tried multiple power cords w/ multiple power jacks, pressed the PMU reset button, and reseated the PSU molex connectors, all to no avail.

I voltage-tested the pins in the PSU's molex connectors, and I did get several readings up to a couple hundred watts. I did not get this result most of the time (though I probably wasn't doing it right). This makes the suggestion that the PSU should be OK, as it seems evident that the logic board appears to be receiving power.

It has an old electronic smell. Nothing close to burning, or suggestive of something previously being fried. The logic board looks fine, nothing seeming to be amiss.

So how often do the QS power buttons fail, likewise their logic boards? And what else can be done?

Thanks, all. Much appreciated. :)
Click to expand...
I know on a standard ATX power supplies, you can use a paper clip, or piece of wire to bridge the connection between the Power On Sensor wire (green) and ground to force the PSU on. But this is a Mac, so I doubt it's power supply conforms to industry standards for pin outs, color coding, etc.. Find the Mac equivalent of that green wire, and you should be able to force power to the board :D lol
 
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sparty411 said:
I know on a standard ATX power supplies, you can use a paper clip, or piece of wire to bridge the connection between the Power On Sensor wire (green) and ground to force the PSU on. But this is a Mac, so I doubt it's power supply conforms to industry standards for pin outs, color coding, etc.. Find the Mac equivalent of that green wire, and you should be able to force power to the board :D lol
Click to expand...
This may help if OP chooses to do this.

 
I'd prefer another way without opening the PSU up, if possible.

What is the likelihood of the switch board failing? I only now got to examine it, and there seem to be white cracks or something of the sort across the back side. Some kind of residue, maybe.
 
I just remembered the G3 keyboards have power buttons on them. I had two around here, but I gave one to someone else and I can't for the life of me find the other one.

Arrgh!
 
OK, I managed to get hold of a keyboard w/ power button, and still no dice. Which means either the PSU or the motherboard is at fault. I suspect the motherboard.

This thing has such a cool case, and I was hoping to have it replace my G5 as primary machine.

Apparently, these QuickSilvers are notorious for their PMU issues. - Rather than spend $40+ on a new LoBo (which is still no guarantee), and potentially risk the same eventual problems, maybe it's time to give modding a shot...
 
XaPHER said:
What about the video card?
Click to expand...

It actually came with two, the AGP GeForce 2MX, and the original PCI Radeon. I replaced my G3's Rage 128 with the Radeon, and performance has easily improved at least 2x, especially with QE manually enabled. Though I still have to repaste it, the experience is really great now.

As for the Quicksilver, I tried everything again with both removed, and it was all the same result.

No one here has experienced this stuff before??

-

I'm thinking of getting a RockPro64 for the mod innards. Secure, energy-saving, space-saving, and expansive... Sounds like a great successor to me.

Sent from AquaWeb on my G3. :)
 
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z970mp said:
It actually came with two, the AGP GeForce 2MX, and the original PCI Radeon. I replaced my G3's Rage 128 with the Radeon, and performance has easily improved at least 2x, especially with QE manually enabled. Though I still have to repaste it, the experience is really great now.

As for the Quicksilver, I tried everything again with both removed, and it was all the same result.

No one here has experienced this stuff before??

-

I'm thinking of getting a ROCKPro64 for the mod innards. Secure, energy-saving, space-saving, and expansive... Sounds like a great successor to me.

Sent from AquaWeb on my G3. :)
Click to expand...
How is OpenGL performance on the rockpro64’s? I’d be interested in buying one, if they can do some really light gaming (I like 0AD).

by the way, I’d at least TRY forcing that thing to turn on by jumping the power supply. At least then you’d know what the culprit is.
 
sparty411 said:
How is OpenGL performance on the rockpro64’s? I’d be interested in buying one, if they can do some really light gaming (I like 0AD).
Click to expand...

I don't know yet, but it's a rapidly growing platform (similar to Talos II), so even if OGL isn't completely there, it will be in due time. The thing only released last year, so it still likely has a little ways to go to full maturity.

sparty411 said:
by the way, I’d at least TRY forcing that thing to turn on by jumping the power supply. At least then you’d know what the culprit is.
Click to expand...

Alright...
 
Alright, with everything plugged in, I jumped the green wire to several ground pins on the 22-pin molex connector with the 4-pin connector still in (why didn't anyone tell me you don't have to open the power supply), and got nothing - not even a wink of life.

I also voltage tested several red and orange wires on the same connector (with the black probe on ground), and got unreliable results. Certainly no sustained 3.3v or 5v readings.

So this seems to indicate that it's the power supply instead... What is one to do now when replacement power supplies are well over a hundred, and donor Quicksilvers themselves are a hundred in shipping alone...
 
z970mp said:
OK, this one's $80.

www.ebay.com

REPAIR SERVICE Apple PowerMac G4 Quicksilver Power Supply QS API1PC12 | eBay

All G4 power supplies are getting old. This will help to insure a long, and trouble free life. I only use top quality parts which are as good, or better than the original parts.
www.ebay.com

But a midrange Rock64 is about $70...

What a dilemma!
Click to expand...
why not just mod an ATX power supply? I find them all the time at the university surplus, Craigslist, etc, for a few bucks.
 
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sparty411 said:
why not just mod an ATX power supply? I find them all the time at the university surplus, Craigslist, etc, for a few bucks.
Click to expand...

According to ATXG4, there are a bunch of compromises in doing this with a Quicksilver, and it's the most difficult to do. Needless to say, I don't think that's an option...

Anyway, thanks for the help.
 
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$80+ For a used old as dirt psu or a $5 thrift psu weekend project. Sounds like a no brainer to me-even with the noted drawbacks if you want your box to turn on. I seriously just passed two $5 NIB old 300w ATX psu ‘s at the thrifts over the weekend. Maybe I should go scoop them after work tomorrow. Just nice to have em in my parts bin.
 
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RhianB said:
$80+ For a used old as dirt psu or a $5 thrift psu weekend project. Sounds like a no brainer to me-even with the noted drawbacks if you want your box to turn on.
Click to expand...

Well, since the DIY PSU is out of my skill (or interest) set, the $80 PSU is not a pursuable value with no true guarantee of reliability (it's the same model), and as I intend this QS to be my successor machine, I've decided to go the SBC route, as ARM seems to have a longer roadmap, greater support, and better performance all around.

I'm keeping everything as authentic as possible by saving as much as possible, including the PSU fan (and framework assemblies, should it ever be put back together); and PSU aside, nothing will be thrown out.

Pretty good overall for a recycler box, if you ask me. :)
 
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Hmm I think that’s pretty cool. Please document/share your build here if you choose to proceed. I think that would be a great read.

I have a 2nd QS case but have been looking for a cheap micro atx build I can stick in there. (Specs not too important ATM) - more about understanding & thinking through the case modification.
 
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Probably stupid question, but can I install the QS' dual 800mhz daughter card into my B/W G3's LoBo? I haven't seen it; will the connector accept it?

Of course, that brings up problems like heatsink placing and clamp holes...
 
z970mp said:
Probably stupid question, but can I install the QS' dual 800mhz daughter card into my B/W G3's LoBo? I haven't seen it; will the connector accept it?

Of course, that brings up problems like heatsink placing and clamp holes...
Click to expand...

Not a stupid question, there are a few (very few) OEM G4 CPU cards that will work in your B&W, but nothing from a Quicksilver will work. The only Apple-shipped G4's that will work in a B&W are from the Yikes! PMG4's. Those use the same ZIF slots as the B&W PMG3's, so Yikes! 350-400 MHz G4 cards will slot right onto your B&W's logic board. They might even be plug & play, but I've never done that so I can't say for sure - there may be firmware updating or some little hackery involved. I just know they'll fit.

Nothing from a Sawtooth or later will fit, and dual processors of any kind are not supported on the B&W.

But there were a LOT of aftermarket CPU upgrades for these machines, which you can learn more about at the following:

Guide to G3 CPU Upgrades: http://lowendmac.com/ppc/power-mac-g3-upgrade-guide.html

Guide to G4 CPU Upgrades: http://lowendmac.com/ppc/g4zif.shtml
 
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FWIW, when another member of this forum visited me a few years ago, he brought along a dual 1ghz QS that displayed similar symptoms as here. I vowed to not let him leave my place until it was working :)

It actually ended up being a bad CPU card, as it started right up once I fitted a known good one. He didn't want the spare dual 1ghz I had lying around, so I ended up forcing him to leave with a single 800mhz.

All of that said, I have seen more dead PSUs in QSs and DAs than I care to count. There's a box in my office with 2 or 3 that I've been meaning to hand over to our electronics guy and see if he can coax some life back out of them, but I also don't have high hopes.
 
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