iMac G5 1.8 Burnt Diode on PCB

[Alfred]

Hi everyone

Thanks for the interesting forum.

Can anyone help me identifying a burnt out diode?

Here is the story thus far.....

iMac would not power up. The On Off LED in button just cycles on and off. Taken to Apple Repair Centre. Swollen caps replaced with new Rubycon MCZ series. This was done under Apple's extended warranty for this problem.

Then 3 months later the iMac again would not power up. On Off LED in button just cycles on and off.

I took it again to the Apple repairer to be told unfortunately the unit was not covered by Apple Care and therefore would not be fixed. I must admit to feeling a bit cheated as this is the same symptom that happened prior to the caps being replaced the first time.

While checking voltages around the PCB I noted that D902 is completely crisped. D900 is just above it and is marked B2Z. Does anyone know this diode's specification? I am not familiar with this type of diode marking.

Does anyone know if D902 would be the same as D900?

These components are just to the right of U2900

My next step will be to try and troubleshoot why this component failed.

The Logic PCB has the following markings:
W85039HQRBYY
1.8GHz 567856

An additional number on the PCB is 820–1540-A

Thanks for any assistance.

Chris

[starfury1]

Re: iMac G5 1.8 Burnt Diode on PCB

the question would be more "Why did it burn up" before you replace it.
fried components usually mean large currents, large currents usually mean something shorted or pulling more then it should (possibly due to some other fault)

Dont know if there is any mac tech type forum members that regularly post here, but sure they will post if the know the answer

If the G5 (tower cheese graters) was one of those early ones....they had a bunch of bad Nichicons I think it was. (and think they decided to ware that problem under warranty)

I find apples reply funny, so did they offer to fix for a price?
(although I think with apple its pcb jockey, not component level repair)

Photos are always nice too, so post one or two of the PCB if you can.
it may give clues or possibly workout its function from them.

Yeah Id be a bit peeved too considering what they ask for them.

Anyway hopefully someone that know macs will post on it.
If your lucky it might be a common type issue with them.

No help at all I know. see what I can dig up on google a bit later

Cheers