Author Topic: G4 DA dying PSU, easy fix or send it off  (Read 2426 times)

Offline mopar300m

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G4 DA dying PSU, easy fix or send it off
« on: January 15, 2022, 10:52:25 AM »
My new to me G4 has a dying power supply.  If I shut the machine down it won't power back up.  Sometimes it will power up if I leave it unplugged for a few hours.  Is this an easy fix, like replacing the low voltage electrolytic capacitors on the secondary side?  I found a guy on ebay (think he's been mentioned here also) that repairs these supplies but he's expensive.  I have electronic servicing tools and would like to save some money but I also want the repair to be reliable.

Thoughts?

Offline chrisNova777

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #1 on: January 15, 2022, 11:11:43 AM »
i had the same problem before - its made no sense to me at the tiem - very frustrating
this is exactly why i posted that post about the atx supply convreter thingy

Offline FBz

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Re: G4 DA / PSU
« Reply #2 on: January 15, 2022, 11:49:24 AM »
Might be pretty cool to try the ATX Power Supply + “converter thingy” as mentioned by Chris
and with total cost result, compared against (I assume, *Andy Cuffe’s re-capping service).
Bearing in mind that Andy did offer forum members a discount.

Or, there’s always the D-I-Y approach… with total necessary capacitors costing under $20.00.
Maybe, just carefully open your PSU (out of the machine) and have a look to see
if you wanna give it a go yourself. Any doubts? Send it to Andy.

*Go through eBay (acxelectronics) and possibly pay more,
or contact Andy via direct email and pay less. acuffe@gmail.com
Be certain to mention that you got his contact info from MacOS9Lives.

Offline mopar300m

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #3 on: January 15, 2022, 12:15:23 PM »
I looked into the ATX conversion but I need that +25v line for an ADC CRT monitor.  I'm good with electronics but my knowledge of multi-voltage SMPS is limited.  I'm already over budget on this project but I'd rather have the peace of mind of a good power supply rather than having to pull it 3-4x for troubleshooting and the possibility of it not working properly.  I had the PSU apart when I cleaned the computer and didn't see any bulging or leaking capacitors.

I'll look into an ATX PSU conversion on my B&W G3.  There appear to be no downsides.  The original PSU still works but it's getting old and works hard.

Offline DieHard

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #4 on: January 15, 2022, 12:30:54 PM »
Search for the "Hair Dryer" trick, should work in your case to buy you time... maybe years

Offline chrisNova777

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #5 on: January 15, 2022, 05:01:17 PM »
hair dryer trick didnt do much for my qs 800 that died back in the day... posts are prob burried here somewhere
i think it was a dual or single 800 qs

Offline IIO

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #6 on: January 15, 2022, 06:22:31 PM »
Is this an easy fix, like replacing the low voltage electrolytic capacitors on the secondary side?

that is basically how you repair them. but it economically only makes sense if you can do it yourself.
insert arbitrary signature here

Offline peeperpc

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #7 on: January 16, 2022, 08:53:55 AM »
I had the PSU apart when I cleaned the computer and didn't see any bulging or leaking capacitors.

You can't judge them by the look alone. When I recapped my MDD's PSU, the most damaged (dropped capacitance, increased ESR) caps
were a few small ones (around 3x11 mm, Ltec branded) which didn't leak. And the leaking one (a bit bigger one on secondary side, Teapo branded)
had a surprisingly not so bad value compared to its apparent condition. A person more knowledgeable than me said on
badcaps forum that those smaller ones were the real culprits that prevented the PSU to power on.
None of the Japanese branded ones were found bad.


I'm already over budget on this project but I'd rather have the peace of mind of a good power supply rather than having to pull it 3-4x for troubleshooting and the possibility of it not working properly.

Yes, it's hard to decide.

Offline Bolkonskij

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #8 on: January 17, 2022, 08:53:59 AM »
The PSU in my MDD started to fail with random lockups and such mid 2021. I have an ADC Apple Cinema HD display hooked up to the MDD, so an ATX mod was no option for me.

Instead, I had the Samsung PSU recapped. It's not easy to work on, so you need to be really good with a soldering iron. I gave it to someone who is. I paid like 70 euros here, which is OK given the thousands of euros I saved over the years by dropping out of the upgrade cycle. So it's a very economical investment to me - if you use the computer just for tinkering and otherwise pour your money into Apple's latest stuff, you may feel it's not worth spending.
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Offline mopar300m

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #9 on: January 19, 2022, 11:12:48 AM »
The PSU in my MDD started to fail with random lockups and such mid 2021. I have an ADC Apple Cinema HD display hooked up to the MDD, so an ATX mod was no option for me.

Instead, I had the Samsung PSU recapped. It's not easy to work on, so you need to be really good with a soldering iron. I gave it to someone who is. I paid like 70 euros here, which is OK given the thousands of euros I saved over the years by dropping out of the upgrade cycle. So it's a very economical investment to me - if you use the computer just for tinkering and otherwise pour your money into Apple's latest stuff, you may feel it's not worth spending.

I plan on using the G4 DA for music stuff and I expect it will work hard and need reliability.  I'm having the power supply repaired by Andy (the guy on ebay).  The more I read posts on this site the more I want a MDD machine so maybe I'll pick up a broken one and tinker with that power supply.

As for my setup I use a modern desktop (AMD FX-6300) and laptop (7th gen i7) for my main computers.  I avoid any Apple products that aren't PowerPCs.  I have a G3 B&W I used until 2008 as my main computer before I retired it.  When I bought the G4 DA, I brought the B&W out of retirement and found it 2 of the SCSI hard drives had failed.  The primary IDE port doesn't work either so I probably need a new motherboard.  I'm getting way off topic here.  I'll post again when I get the supply repaired and reinstalled.

Offline mopar300m

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #10 on: January 25, 2022, 05:25:29 PM »
The power supply is finally on its way to Texas.  I should get it back in a few days.

Offline Bolkonskij

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #11 on: January 26, 2022, 08:59:07 AM »
Good decision! Report back how it runs with the overhauled PSU, please :)
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Offline mopar300m

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #12 on: February 01, 2022, 06:26:32 PM »
I got the PSU back and it seems to work fine but the rest of the computer doesn't.  It won't turn on with the power button.  I can get it to come on by unplugging and replugging the power button board.  Sometimes it will go into programming mode and drop into open firmware.  I tried different memory and another video card.  I'm basically back to square one with this computer.

Offline GaryN

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #13 on: February 02, 2022, 01:25:25 PM »
I don't own a DA BUT it's a good bet that somewhere on the main board there is a small button labeled "PMU". That would be for "Power Management Unit" a subsystem that minds and regulates things power-related. It's needs a reset.

1) Unplug power
2) Remove battery and either test/verify (or better) replace with a new one
3) Reinstall good battery
4) Press PMU button once and only once.
5) Reconnect power
6) Close eyes…tell Steve Jobs you really didn't mean all of that nasty shit you said about him
7) Press power button

If you're lining right, the computer will start up from then on

Offline mopar300m

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #14 on: February 11, 2022, 12:43:47 PM »
I followed GaryN's instructions to the letter, even replacing the PRAM battery with another new one.  No luck.  I can get the computer to power on by unplugging, replugging and unplugging the power button board.  If I leave the power board connected, the computer will shut down after a minute.  I had the computer on for several hours and it was stable.  I installed OS9 from the macos9lives CD without a problem.  I tried installing OS X but the crummy aftermarket DVD-RW was having trouble with DVD discs.  The proprietary H/K softball speakers played loud.  I haven't tried my ADC CRT monitor yet.

The refurbished supply works great and Andy said it would be fine for several years.

Since I have a known good power supply now, the next step is troubleshooting the boards and cables.  I've put this computer to the side for now as I've been working on restoring my B&W G3.

Offline GaryN

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #15 on: February 11, 2022, 10:48:55 PM »
I can get the computer to power on by unplugging, replugging and unplugging the power button board.  If I leave the power board connected, the computer will shut down after a minute.
Thinking logically, that sounds like the power button is stuck or internally shorted in the depressed position.

Offline mopar300m

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #16 on: February 12, 2022, 10:50:06 AM »
I thought the same thing so I checked the pushbuttons with a multimeter and they are all working fine.

Offline GaryN

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #17 on: February 12, 2022, 02:36:13 PM »
A short on the board then? If the:

Computer powers on when you plug the board in… like it would shorted
Stays on if you leave it unplugged… like it would if unplugging removed the short
Shuts down if you leave it plugged in… like it would shorted because it takes a minute to shut down if you just push power and hold it

The fact that shit happens with the power board connected and doesn't with it DISconnected screams that's where the problem is.
Again, I don't have a DA. What else is on that board? Is there 5 or 12v supplied to illuminate the button? Any other parts?
An open or shorted diode or LED could maybe cause weird stuff to happen…


Offline FBz

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #18 on: February 12, 2022, 03:37:18 PM »
AGP vs. DA...





Offline GaryN

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Re: G4 DA dying PSU, easy fix or send it off
« Reply #19 on: February 13, 2022, 04:55:40 PM »
Oh hell… I rest my case. Time to replace the board.

Thank you Fbz.  :P

 


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