iMac G5 wont start

[JoyBed]

Hi folks! I finally got something with a G5(I know i wanted a PMG5 Quad, I am still searching for one). Its a iMac G5 this one https://everymac.com/systems/apple/imac/specs/imac_g5_1.8_20.html with 2 gigs of ram installed. The thing is it was for sale as "for parts/repair". When I try to turn it on the light in the down right corner lights up and just the diagnostic LED 1 and 2 are lit up. No backlight, no fans, no sound, no nothing... First thing I noticed are the caps on the boards. Any other idea?

 

[Raging Dufus]

These were known for bad capacitors.

https://www.cnet.com/news/pcs-plagued-by-bad-capacitors/

Whatever other problems there may be (and there might not be any), the caps are where you're going to have to start.

 

[sparty411]

I can see bulging caps in your pictures, like you said. Replace them, then go from there. In my experience, replacing bulging caps solves no boot problems roughly 90% of the time.
[doublepost=1563974224][/doublepost]

Hi folks! I finally got something with a G5(I know i wanted a PMG5 Quad, I am still searching for one). Its a iMac G5 this one https://everymac.com/systems/apple/imac/specs/imac_g5_1.8_20.html with 2 gigs of ram installed. The thing is it was for sale as "for parts/repair". When I try to turn it on the light in the down right corner lights up and just the diagnostic LED 1 and 2 are lit up. No backlight, no fans, no sound, no nothing... First thing I noticed are the caps on the boards. Any other idea?

View attachment 849646 View attachment 849647 View attachment 849648

 

[JoyBed]

So far I replaced all the caps in the power supply and these six on the mobo. The error persists. I cant source the other caps in my local shop or in my work. Sorry I forgot to take a picture of the PSU.

 

[Eriamjh1138@DAN]

You still have some bad caps to the left of the G5 Heat sink in the first pic. Replace all of the caps of any type if a single one of them is bulging.
You can buy caps from mouser.com, digikey.com.

 

[sparty411]

So far I replaced all the caps in the power supply and these six on the mobo. The error persists. I cant source the other caps in my local shop or in my work. Sorry I forgot to take a picture of the PSU.

View attachment 849719

I counted 13 bulging caps on the main board. I highlighted them in your pic I edited.

 

[JoyBed]

I counted 13 bulging caps on the main board. I highlighted them in your pic I edited.

Dont worry I see them, but as an electrical engineer I dont trust even the good looking ones that are parallel to the bad ones. So its 18 to replace without the 6 I already replaced.

 

[tigerintank]

You can swap the iMac PSU for a standard PC PSU with some pin swaps in the connector. Iirc there's a post on this sub forum somewhere

 

[Eriamjh1138@DAN]

JoyBed asked for a pics of my mobo questioning missing caps. It is not uncommon for some components to not be populated in final production.

Here's my 1.8GHz G5 non-iSight mobo. It's never been recapped. Either it hasn't been used much or I got lucky.

 

[tigerintank]

Also lucky with Mobo. PSU not so much

 

[JoyBed]

JoyBed asked for a pics of my mobo questioning missing caps. It is not uncommon for some components to not be populated in final production.

Here's my 1.8GHz G5 non-iSight mobo. It's never been recapped. Either it hasn't been used much or I got lucky.

View attachment 850232

Thanks for this photo! I am missing some resistors and two transistors... Now just to kill myself. I can ask for you to measure the the resistors for me but you cant just slap any transistor there. I want to cry.

 

[z970]

@JoyBed We've all had problems like this along the line.

We've got you...

 

[Eriamjh1138@DAN]

Maybe you can find your values in this list of Apple mobo part numbers. You may have to google the PN for the iMac G5 first.

 

[rslanna]

it is a little bit dumb question but... have u tried to test the RAM modules? i had a G5 17'' here with same problem as you and even after recapping it won't work at all.
i solved replacing the ram modules

 

[Alexis Trinquet]

IIRC the diagnostic LED 1 lights up whenever there is a trickle voltage from the PSU has been detected, the 2nd LED lights up normally when the computer is turned on and that the PSU is powering the board.

Now if LED2 is on but the compter does not fire up... Seems like the fault is in the logic board somewhere.

 

[JoyBed]

IIRC the diagnostic LED 1 lights up whenever there is a trickle voltage from the PSU has been detected, the 2nd LED lights up normally when the computer is turned on and that the PSU is powering the board.

Now if LED2 is on but the compter does not fire up... Seems like the fault is in the logic board somewhere.

Then it’s the missing resistors and transistors. The pads look like someone took them off. IDK why...

 

[Alexis Trinquet]

Probably someone tried to cannibalize it for parts, I don't really know this machine very well, so that's about it when it comes to what I know about iMac G5s.

 

[JoyBed]

JoyBed asked for a pics of my mobo questioning missing caps. It is not uncommon for some components to not be populated in final production.

Here's my 1.8GHz G5 non-iSight mobo. It's never been recapped. Either it hasn't been used much or I got lucky.

View attachment 850232

Thank for the photos. it helped me a lot in searching what components are missing. There was like 20 resistors,2 caps, 2 coils, 1 transistor and 1 diode missing. Can you please make a picture of the whole board from both sides? In good resolution so I can compare it to my board. But still it doesnt boot. Power light is on, diag led 1 and 2 are on. but no fans turning, no backlight, no chime. After a while powered like this led 4 light up so it starts to overheat without the fans. Either there are some more missing components or the GPU is dead and I need to replace it. Did someone tried just swapping the PPC970 for 970FX ? Also I noticed the unpopulated sata connector that is marked as DEV. In schematics of the board between the DEV sata connector and the chip that controlling the sata there are just 4 ac decoupling caps. I am curious to see what happens if i solder on the caps and the connector and plug a drive in there.