Power Mac G4 (Gigabit) PSU woes, x2!

[M235i]

I recently bought a Power Mac G4 Gigabit (450DP, 128MB) at a thrift shop. It was working when I tested it at the store, and it powered on and attempted to boot it. When I got home, I hooked it to my ADC Studio Display it powered on fine, but had a kernel panic before it could fully boot to the operating system. After taking the HDD out to replace it with another IDE drive, it now fails to so much as turn on. Different power cords and displays failed to repair this, as well as a CUDA, SMC, PMU and RAM reset, reseat, and replacement. 

I then put that to the side and two weeks ago picked up another PM G4 Gigabit for free at VCF East on the last day in an attempt to fix the other one. Got that home and also proceeded to power on at all. Nothing seems to be unseated, and I can only assume that I will need a new PSU, which I cannot find a good replacement for under $50, which is crazy. I am aware of the ATX-to-G4 PSU mod, but I would really prefer to still have the ADC power available to the Studio Display. 

Would it be possible to reflow the PSU? I have a guide that I am ready to use, but I am not sure that it will be a permanent fix? Any ideas on repair?

 

[Byrd]

Hi M235i (nice car),

I'd strip it down to the bare minimum and see if you can get power and a chime.  Try a known good stick of RAM, pull the video card (and ADC monitor, needless to say), IDE cables.

 

[Jinnai]

Oh man, I had a lot of those a few years ago and the whole thing was a mess. I think most of the problem was PSUs as well, but couldn't be sure it wasn't quirks with the PMU or IDE or whatnot.

 

[M235i]

Hi M235i (nice car),

I'd strip it down to the bare minimum and see if you can get power and a chime.  Try a known good stick of RAM, pull the video card (and ADC monitor, needless to say), and IDE cables.




 

Thanks for the advice, I never thought about that. I will try to report back on what that gets me when I get the chance. 

PS: Love the car too, I have been using this username since 2011 when the 1 series was still a thing in the US, I never thought the 2 series would be a real BMW lol. 

 

[M235i]

UPDATE: After disassembling the PSU (which had tested faulty), it looks to be a transformer or a fuse on the voltage regulator board in the PSU. The model is seen as a Wan Nien 03c30-00011. Google has come out completely dry, and there is no way to determine what the transformer specs may have been. Has anybody ever gone this far into a PM PSU? The PSU is ACBEL-API9841

 

[davidg5678]

Does your PSU make a very quiet clicking noise when plugged into the wall? My Quicksilver's broken PSU does this while pulsing very small amounts of voltage (off then on) through the power rails. I attempted to take apart my PSU, but I had trouble locating what was clicking. This was as far as I got as I did not want to check things with my multimeter while it was plugged into the wall.

In theory, it is possible to perform the ATX-to-G4 mod and use a Boost Converter to provide the higher voltage used for ADC power.

https://www.amazon.com/3V-32V-5V-48V-Output-Adjustable-Converter/dp/B01MS3IAVL/ref=asc_df_B01MS3IAVL/?tag=hyprod-20&linkCode=df0&hvadid=343288438787&hvpos=1o3&hvnetw=g&hvrand=1861675565975819191&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9006604&hvtargid=pla-737249670421&psc=1&tag=&ref=&adgrpid=68271436279&hvpone=&hvptwo=&hvadid=343288438787&hvpos=1o3&hvnetw=g&hvrand=1861675565975819191&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9006604&hvtargid=pla-737249670421

 

[hoi polloi]

What is the latest on this?  Were you able to repair or replace the PSU?

 

[M235i]

What is the latest on this?  Were you able to repair or replace the PSU?

Well, I was never able to find what went wrong in the power supply. All of the multi-meter tests showed that it was working properly, so something had to had gone wrong within the voltage regulator board or there is a capacitor that I missed. I traded the machine for a Performa 600 but I still have the other G4 here that had yet to be disassembled. I just do not have the time right now to investigate it. I hope to get some more results in the future, but right now this is on hold.