G5 Mac Power Supply Relay

[torgeson5kqs]

Re: G5 Mac Power Supply Relay

With DVM set to (1000 VDC on my meter) and red probe set on cathode end of D2 then jumpering with wire from green to black on P2 reading stays steady at 393v then removing the jumper D2 drops for some time down to about 158-162v. This was done several times. Also unplugged unit and waited for voltage to go down to zero on D2 then did procedure again. Same results.

As was expected when jumpered relay clicked and fans (PSU fans) kicked on and then when jumper removed fans kicked off and D2 started to decrease in voltage.

[Toasty]

Re: G5 Mac Power Supply Relay

With it jumpered, please check the 3 output voltages again measuring from the board negative point to P2.

Reason: With the relay on, the 393v is present. When it is off, the mains power is removed from that side of the supply and you would only see the ~160v. The 393v supplies the output power side of the PSU....

[torgeson5kqs]

Re: G5 Mac Power Supply Relay

I've got voltages on all the colors/pins you mentioned.

Yellow=11.9v
Orange=3.4
Red=5.1

[Toasty]

Re: G5 Mac Power Supply Relay

It's working then. So the initial readings were not correct. Re: Post 2 & 3



Must be because you were reading from the chassis, not the negative wires.

If it fails when connected to the system, there's a problem with the system, not the PSU.

Toast

[torgeson5kqs]

Re: G5 Mac Power Supply Relay

Any idea's/suggestions on what I should check out?

[Toasty]

Re: G5 Mac Power Supply Relay

I don't have any experience with these systems other than the PSUs.

It would seem that something is overloading the PSU. Try disconnecting any peripherals such as drives or video cards or add-ons.

If you can provide a good pic of the mainboard, perhaps I can give you some ideas.

[torgeson5kqs]

Re: G5 Mac Power Supply Relay

But the supply back in with just fans and cpu water cooler plugged in. No cards, drives, etc. What do you know..... Heard the apple chime and turned right on.

I will just work on systematcaly plugging in drives and cards now. I can't say enough however, for you helping me on this PSU. It's been a good learning experience, these are so much better built than the PSU's on the iMac which I've repaired about 15 of. Much of the info I've gotten from reading your posts to other's who have had similar problems. Thanks, again. I'll post again when I think of narrowed it down to problem part.

[torgeson5kqs]

Re: G5 Mac Power Supply Relay

It's the video card. The guy I bought this from apparantly must have ripped the video card out of the socket somehow and took off about 5 SMD caps with with it. Odd though that the whole system would go down just be cause of some SMD caps on a video card.

[Toasty]

Re: G5 Mac Power Supply Relay

Excellent! Case closed.

[camfi]

Re: G5 Mac Power Supply Relay

Hi guys.
I have this power supply for repair from my friend. It cannot be turned on. relay is not clicking or something.. Fuses are ok, rectifiation part is ok, but it has blew out transistor Q8 and resistor R68 on back side. because they are non readable can anyone tell me their values please? I was searching for schematic diagram, but wasn´t succesfull.
Thank you for your help.

[abblanco]

Re: G5 Mac Power Supply Relay

I was read this interesting post but in ultimate test D8 don`t down to 160v. :-C

Q8 is 1P and 7 in horizontal position, identical to Q2
R68----------472

[mantis01]

Re: G5 Mac Power Supply Relay

Toasty

I wonder if you could help on this old post. Your instructions are extremely through. I have this same power supply and followed through all of the tests and they all check out until "With it jumpered, please check the 3 output voltages again measuring from the board negative point to P2." I have no voltage on P2 with the the jumper I just get a double click and the fans move slightly. Any help would be greatly appreciated.

[Toasty]

Re: G5 Mac Power Supply Relay

Make sure you read the wire color correction in post 14.

Without the relay powered, there is no 393v so that means the trouble is either in the standby circuit or the PFC circuit or both.

The relay can't be powered until the standby is working correctly.

Following the instructions in Post 10, are you getting the same (or close) voltages as in Post 11?

T

[mantis01]

Re: G5 Mac Power Supply Relay

Make sure you read the wire color correction in post 14.

Without the relay powered, there is no 393v so that means the trouble is either in the standby circuit or the PFC circuit or both.

The relay can't be powered until the standby is working correctly.

Following the instructions in Post 10, are you getting the same (or close) voltages as in Post 11?

T

Thank you for replying to this old post. I just now saw that you responded.
here is what I have on my supply


Leaving the negative probe in place on D24, measure and report the voltages at the cathode end (banded) of the Zener diodes to the right, up by the sealed trimmers, and a few more below them. I'll list them in order coming down the board: 5.1v

ZD9 11.8v
ZD8 11.8v
ZD10 (next to lower heatsink) 4.9v
ZD7 (left of 3 small caps, cathode is lower connection) 12.6v
ZD11 (left of 3 small caps, cathode is lower connection) 24.3v

With the negative probe still on D24's anode, measure and report the voltage on Pin 1 of each of the 5 optoisolators. They are the square little devices with 4 legs above the trimmers. 4 white and 1 black on mine. Pin 1 is the lower left pin. If you look at them closely, the pad they are soldered to on the board is square, and there is a dot on the body of them. Be careful not to short the pins on these.

M5 22.6v
M2 0v
M12 12.7v
M7 12.7v
M8 5.1v

Remove the negative probe from D24.

[Toasty]

Re: G5 Mac Power Supply Relay

It seems as though there is nothing wrong with the PSU. I suspect something in the system is causing the problem. Do as post 27 discussed and disconnect everything except the essentials. Try connecting one at a time, powering down before installing or connecting the next device.

T

[mantis01]

Re: G5 Mac Power Supply Relay

When I jump the green to black on P1 I get a double click from the relay but there is no voltage on the Red yellow Orange on P2.

[Toasty]

Re: G5 Mac Power Supply Relay

No. Put it back in the system. No jumpering here. It needs the system to signal PG.

T

[abblanco]

Re: G5 Mac Power Supply Relay

Hey! what happened? I am very interesting in resolution?

[keithf2]

Re: G5 Mac Power Supply Relay

Is there anyone still working on this forum.

[Toasty]

Re: G5 Mac Power Supply Relay

You mean thread, not forum. And yes to your question.

T