Imac G5 - Issue or not?

[Markie76]

Hi Guys,

Wanted to get your opinion on an old Imac G5 20" desktop (model: A1076) I got a few years ago to dip my toes in the other side of computing and what it does when I turn it on.

This what happens;

1. I plug it into the mains.
2. I press the power button - nothing happens.
3. I unplug it from the mains.
4. I plug in back into the mains - it makes gentle random high-pitched/frequency noises.
5. I press the power button - white light illuminates on front then fades out and it makes a ding/bing noise and looks like its starting up.
6. When the white screen appears the high-pitched/frequency noise increases in volume.
7. The white screen seems to flicker a couple of times - high-pitched noise continues the same.
8. When the screen changes from white to the blueish login screen the high-pitched noise reduces significantly.
9. When I login to the desktop - high pitched noise is either gone or hardly noticeable.
10. It seems to work as normal.
11. If I restart it works.

I always unplug it from the mains when not in use - so next time start at point 1.
I don't use it regularly.


Should I prepare my screwdriver and soldering iron?

Thanks,

Mark.

[Topcat]

Re: Imac G5 - Issue or not?

Sounds like the power supply is getting ready to bite the big one. Might as well recap the motherboard too.

[gabik111]

Re: Imac G5 - Issue or not?

Inside on the mainboard there are 4 status LED lights. During normal work three of them should light steady.
1- power supply works correctly
2 - logic board detected corrected voltages and works properly
3 - LCD and logic board are communicating
4- overheating detected

[Hoss]

Re: Imac G5 - Issue or not?

Do NOT rely on the power supply being ok if the first LED lights up.

9 out of 10 bad power supplies will light up the first LED.

[Markie76]

Re: Imac G5 - Issue or not?

Thanks for your replies guys.

I have done some investigation and removed the back on the imac.

STATUS LED LIGHTS:
1. When I plug in the power to the mains the first LED comes on and also the second LED is on but quite dim.
2. After 20-25 seconds the second LED goes out.
3. After about 60 seconds the PSU makes gentle random high-pitched/frequency noises.
4. I press the power button and it powers up.
5. Once booted the first 3 LED lights remain on.

See pics.

MOTHERBOARD CAPS:
The motherboard caps all look solid - can't tell from this side if they've been replaced.

See pics.

PSU UNIT:
1. It looks like there are 3 bulging caps (2 x 1000uf 10v & 1 x 2000uf 10v).
2. Looks like it has been repaired before.
3. PCB side looks like flux not cleaned off.
4. Covered in loads of 'grey stuff'.

See pics.

So, I'm going to replace the bulging caps - I will most likely replace all the blue caps. And clean the pcb side thoroughly.

BUT

1. If the psu has been repaired before, is there anyway I can check if these cap values are the original spec or uprated?

2. Should I replace with 16v spec caps?

3. What is the grey stuff and should I reapply generously like has been done before?

Thanks,

Mark.

[shovenose]

Re: Imac G5 - Issue or not?

Replacing the bulging/leaking caps in the PSU should solve your problem.

Don't put the glue back. That shit sucks, makes is super hard to remove the caps