I mac G5 PSU, ALS - odd voltages...

[Toasty]

Re: I mac G5 PSU, ALS - odd voltages...

>>C45 has badly burned pads, I think it's shorted into the 3.3V trace. And the two coils on the 3.3V line are increasing the voltage to 47V. <<

Nah.

C45 is the 5vsb output filter cap. VS pad on your pic.

If the board still looks like that pic, grab some 91% isopropyl alcohol and a toothbrush and clean that mess up. Then, reflow all the caps to get nice looking joints and a solid connection between top and bottom of the board. A cold solder joint can act as an antenna for high frequencies. With the standby singing at 40-60kHz, strange things can and do occur.

Going waaay back in this thread (post 6), I said that this could be an induced voltage from the standby transformer. I don't see any chip cap or resistor missing from your pic compared to mine.

Clean it up and plug it into system. If the 47v disappears, I think you're good to go. If it stays, try it and see how the system operates. The current is so low it won't be a problem.

Toast

If you're still not comfortable, I can take a look at it here if you care to do so. I have the same unit here to directly compare it to. Or, you might just be better off getting another unit...

T

Isn't there a Celetronix knocking about too, or was that someone else?

[Toasty]

Re: I mac G5 PSU, ALS - odd voltages...

*bump*

[Sovereign]

Re: I mac G5 PSU, ALS - odd voltages...

can someone help me please with an 614-0293 PSU for Imac G5 17" which gives less than the normal voltages on all pins. With it jumpered without it jumpered it just gives 15 and 22 but same voltages as below. I'm not really good with electronics and used caps that i found at a store near me to change the old ones. Some of the old were blown like the 4700uf 6.3V and 16V 1200uf one.
1---2.1
2---2.1
4---3.2
6---3.2
8----3.2
9---3.2
10---7.7
12---2.1
13---7.7
19---7.7
20---3.2-3.3
21---3.2
22---15.1

I'm trying to get it back and working. Please help.

[Toasty]

Re: I mac G5 PSU, ALS - odd voltages...

Improper caps are the problem. These PSUs *require* specific types of caps (low ESR, high ripple), which this forum is all about.

Read / search the other Apple iMac PSU threads to learn which to go with for yours.

Toast

[trex66]

Re: I mac G5 PSU, ALS - odd voltages...

Thanks toasty, since the pics I posted, I did clean it up and re-flowed the pads.

After changing the small caps and cleaning and re-flowing and replacing the 1P - the voltages weren't continually climbing like before so even though the voltage leaking issue wasn't resolved I thought it just might be stable. I was wrong, the Imac still shuts down whenever it wants to. So whatever the problem is that will make it shut off is still there.

Note, it doesn't matter if the Imac is under load or sleeping, it will just shut off at different times. When it's sleeping is it just getting the trickle Voltage?, if so then that must also be shutting off or I wonder if it's JUST the trickle voltage that is stopping and if it's interrupted the Imac shuts off? After a shut off, the PSU will immediately come back on when the power button is pushed...

I have replaced the PSU with another one and the Imac runs fine and doesn't shut off. So the issue has to be with the PSU.