iMac G5 17" No ALS PSU bad

[KSteinick]

Paging Toasty...

I have an older iMac G5 17" that won't start. Found 5 bulging caps on logic board. Replaced all caps on board. Still no start. Bought "used working" logic board. Still won't start. Have had LED 1 lit with original board, recapped original board, and now used board.

Checked PSU and found 5v and 24v out good without jumping. But when jumping I do not get any other voltages. I have ordered another used PSU because my kids really want the computer back, but I would like to take on the PSU challenge.

It is a Celetronix Q45A - NPFC, 100-120VAC, 5.0A. 50-60Hz, 180W
Apple #614-0294

I will try and get some pics up tomorrow as I work evenings and need to go get ready for work.

Thanks
Kris

[KSteinick]

Re: iMac G5 17" No ALS PSU bad

Pictures of board. None of the caps look bad.

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Will try later.

[KSteinick]

Re: iMac G5 17" No ALS PSU bad

OK they went this time!!

[Toasty]

Re: iMac G5 17" No ALS PSU bad

Search the forums for 'celetronix'.

There is info in those threads as to how to test. IIRC, doing a resistance check from ground to 3.3v, 5v, and 12v outputs will show which output (and MOSFET pair) is shorted. These transistors are damn near impossible to get any more and the last guy got them from Europe at a premium. They must be replaced together as a pair per output. When the one dies, the other typically is damaged in some manner. I've done single replacements, only to have the other die in a minute or two. Then it takes out the one that I just replaced. Very frustrating.

There is also a problem of either leaky transistors or diode. To the right of 2 MOSFETs in the center of the board and Left and Down from the optoisolators. It looks as though you have some discoloration of the board there. Typical. That is another problem and must be fixed -first- otherwise the MOSFETs pop within 30 seconds.

All in all, I have warned people away from these PSUs as they are not cost effective on the repair if dead as yours is. If you get one while still working, a total recap with Panasonic FM's (equal or above) is the trick.

I started doing research into this problem, but when faced with transistors at $10 a pop (literally), it quickly becomes uneconomical to even experiment.

Get a new one or refurb *with guarantee* from a high-rep seller on Ebay. Make sure it is not a Celetronix. ASK the seller if the label isn't shown or they don't tell you the make.

Get the computer working, the kids happy, and report back. If you are not interested in repairing the Celetronix, I'll offer you $20 including shipping for the old one.

Toast

[KSteinick]

Re: iMac G5 17" No ALS PSU bad

Thanks for the quick info!

Will do some more research here at work tonight.

I did notice the discoloration on the botom of the board but think it may just be dust. I was in a hurry to get pictures up for you to see that I did not clean anything up very well.

[Toasty]

Re: iMac G5 17" No ALS PSU bad

It's not dust.

Be careful around and with the litz wires from those transformers. They appear to pliable/flexible. They are not. They are fine enameled wires and can be damaged if you're not careful. Getting components out from under them, is best accomplished by desoldering the offending ones from the board and moving them just enough to allow the component to be removed.

Toast

[KSteinick]

Re: iMac G5 17" No ALS PSU bad

I see that after looking at some pictures in the other thread. I also think the discoloration is similar to the one you were working on near the center of the board around that diode.

PM me your address and I will send this your way.

Thanks
-Kris

[Toasty]

Re: iMac G5 17" No ALS PSU bad

Did you do a resistance check on the outputs and see if anything shows shorted?

[KSteinick]

Re: iMac G5 17" No ALS PSU bad

OK, 12v inner FET shorted. Checked with DMM set in diode mode. The inner FET acts different than other FET's on secondary side of board. It is also a PHD101NQ03LT.

Toasty it is headed your way!!

[Toasty]

Re: iMac G5 17" No ALS PSU bad

Yup, that's the symptom that I've encountered. I found Allied Electronics has these sourced from outside US. Items are minimum qty. of 5 (pack) at ~$1.50, plus a Min Order fee of $10-$15 for less than $50 plus a handling fee of $20. Right off the bat we're at $30 and I haven't even gotten to the items or the shipping... :P:

BTW - that can go Priority Mail in the Small Flat Rate box for $5.

Thanks!
Toast

[KSteinick]

Re: iMac G5 17" No ALS PSU bad

If I was to purchase "some" PHD101NQ03LT's from Allied, do you think they would repair this PSU? I saw on the other thread that there was also a diode that was HOT!! Same spot where mine is discolored. Are there any other problems with these? All caps look good in PSU. The logicboard had 5 puffy 12v caps.

It is boxed up ready to go but for less than $40 it might be fixed?????????????

Nah!!! Add it to your spare parts collection Toasty

[Toasty]

Re: iMac G5 17" No ALS PSU bad

It -might- be fixed for $40, but without diagnosing what -caused- the failure, it's a crap-shoot at best. I am fairly certain the source of the trouble is in that discolored area. As to what specific part(s), I will -eventually- find out.

Toast

[trex66]

Re: iMac G5 17" No ALS PSU bad

I have the same PSU, same problem, almost identical pics - did you ever find the problem in the burned area?

[Toasty]

Re: iMac G5 17" No ALS PSU bad

No time to sit down with it or the others. Most of the "standard" AcBel units are quick (and inexpensive) fixes consisting of caps and an isolated transistor or two.

I'm fairly certain it's a timing issue coming from that discolored area. It's causing one of the MOSFETs to stay on too long. It will take one out even under no load.

Toast

[trex66]

Re: iMac G5 17" No ALS PSU bad

I was hoping you had found the problem... I got bunch of quotes back for 6 PHD101NQ03LT's all around 12-15, the best was $10 shipped. I think I could replace the ones that are suspect, but if the over heated area is going to cause problems then I might be wasting my time.

The only reason I bought this Imac was because the seller told me it had a working PSU - Toasty, you've seen a lot of PSUs, are these worth fixing or should I cut my losses and buy a working one?

[Toasty]

Re: iMac G5 17" No ALS PSU bad

I have not had the time.

Unless you're able to diagnose and fix it inexpensively, then cut your losses.

Don't buy another Celetronix one. Buy the AcBel unit. Even a bad one of those (generally speaking) can be fixed for <$20 worth of caps & s/h.

If you decide to do so, I'll make the same offer to you for the old one as I did KSteinick. It will fit in the small Priority Mail box for $5 shipping, so you'd get $15 for the old one.

LMK by PM if interested.

Toast