Acbel (from Intel iMac) power supply dead -- any hope?

[melb]

Re: Acbel (from Intel iMac) power supply dead -- any hope?

HI, we have an identical PSU in our MAC and it has a blown resisitor (R050) 5W 0.05 ohm i beleive. Could be other issues but this was standout obvious. This is the SMD shown in the board underside of the photos at beginnning of this thread (near top right) As it was such a low value I chose to temporaoily replace it with some resistance wire to act as a fuse and see what happens - it blew again when powered up.

So I have 2 questions:
1. on the PSU it implies it is 12V out put (15 A) - does anyone know the pinout of the 5 pin outlet connector (I am wondering if I can temporarily replace with an external 12V PSU just to prove the rest of PC is OK - it's been sat around a couple of years)
2. Any ideas on what else might have failed on PSU or if my 'fuse' wire concept was a bad one... I just don't want to invest a lot of time/money on futile exercises (we live in New Zealand)

Thanks in advance

[stj]

Re: Acbel (from Intel iMac) power supply dead -- any hope?

check if the fet on the heatsink above the resistor is shorted.

[Toasty]

Re: Acbel (from Intel iMac) power supply dead -- any hope?

Welcome!

See post 20. 12v is the only output, grey(+) & black(-). Brown is "sense". Replacement PSU should work for testing.

Main switcher FET is bad. Resistor is in the path to it from the bridge rectifier. Your main cap could have failed or the PWM switcher IC or both.

T