iMac G5 20" Power Problems

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Hello Mac Users, I received this iMac G5 20" no ALS for free with a power problem. Pressing the power button does nothing. Researching online on possible solutions I discovered about the bad caps on the logic board and even in the PSU so I decided to open it up and look inside. Found about 5 caps bulging up so I bought the caps replacement kit on eBay and replaced ALL of them even the ones that looked OK (What a PAIN to remove and put the new ones in that was). Replaced them all and reconnected all but still no luck. Diagnostic light #1 comes on when power is connected.

So, I directed my attention to the PSU. This time instead of replacing the caps in the PSU, I decided to buy another one online that claimed to be a working one. Plugged the new PSU in but still no luck. One small difference is that when I press the power button, diagnostic light #2 and #3 quickly flash on then off and nothing. I can hear the PSU make a faint click during the flash.

Thinking it was another bad PSU, I decided to buy another one online reported to be in fully working conditions but I have the same problem with the #2 & #3 light flash quickly then nothing.

I guess there is still a problem with the logic board but other than reflowing the caps (which I really would like to avoid since they hols on the board a horribly tight) I have no idea what else it could be.

Any idea what could cause the diagnostic light 2 and 3 to flash quickly then go off? Possible short somewhere?
 

pigoo3

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iMac G5's had issues:

- bulging/leaking caps
- bad video
- and with age & use…power supplies eventually wear out

If the cap replacement went ok. And you've tried at least 2 power supplies that were supposed to be "good"…then the logic board (other than the caps) would certainly be the problem to suspect. There's really not much else that would keep the computer from powering on (at least).

One thing I wasn't clear on (using at least one of these two replacement power supplies)…is the computer actually powering on (fan's start, HD spins, LCD lights up)?

- Nick
 
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iMac G5's had issues:

- bulging/leaking caps
- bad video
- and with age & use…power supplies eventually wear out

If the cap replacement went ok. And you've tried at least 2 power supplies that were supposed to be "good"…then the logic board (other than the caps) would certainly be the problem to suspect. There's really not much else that would keep the computer from powering on (at least).

One thing I wasn't clear on (using at least one of these two replacement power supplies)…is the computer actually powering on (fan's start, HD spins, LCD lights up)?

- Nick

Hi Nick,

Thanks for your reply. No, no fans, no HD and nothing seems to come to life when I press the internal power button. I also tried the SMC reset button right below the power one. All I see when I plug the power cord in is light #1 comes on and stays on as long as the cable is plugged into the outlet. I press the power button and light #2 and #3 flash on and off really quick, the PSU makes a faint click during that quick light flash and nothing else shows sign of power.
 

pigoo3

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Thanks for your reply. No, no fans, no HD and nothing seems to come to life when I press the internal power button.

Are you saying that you are only pushing the internal power button? If I remember correctly…some (or all) of the iMac G5's have a contact switch of sorts that engages when the back cover is replaced.

I pretty sure without the back panel being replaced first...the computer won't power on (unless these contacts are pushed down manually). Again if I remember correctly…these contacts are one or two spring-loaded pins.

- Nick

p.s. I'm assuming that this is the 1st generation 20" iMac where the rear panel is removed to access the inside (later models the front bezel is removed).
 

dtravis7


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Nick might be onto something with that. The First 20" iMac G5 and I believe even the 2nd one with ALS had the back come off. Maybe they put some interlock switch that would not let it power on with back off.

The last 20" iMac with the iSight was the one that the front came off as well as the white Intel iMacs. Mine after 7 years had many bulging caps.
 

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Just went to ifixit to see if they had a photo of what I was talking about. In the photo you can see the two brass-colored pins (next to the tip of the spudger):

2AIAYFjVZS6ixA3e.medium


- Nick
 
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Are you saying that you are only pushing the internal power button? If I remember correctly…some (or all) of the iMac G5's have a contact switch of sorts that engages when the back cover is replaced.

I pretty sure without the back panel being replaced first...the computer won't power on (unless these contacts are pushed down manually). Again if I remember correctly…these contacts are one or two spring-loaded pins.

- Nick

p.s. I'm assuming that this is the 1st generation 20" iMac where the rear panel is removed to access the inside (later models the front bezel is removed).

Ain't that the cats meow!!!! Sorry, it's what I could think of in this case after I heard it from a gentleman here in south USA LOL. Still don't know what it means but I believe it is perfect for this case :)

YES!! I have those two pins and if I touch them with a metal thing, they do the same thing as if you press the small power button. No where on line anyone states to put the friggin cover back before attempting to power it on. I am not at home at the moment but I will sure try later and let you know. My question is: WHY even put the darn power button on the motherboard when I have to put the cover back on to power it on?? In any case, I will report back as soon as I put my hands on it.

Thanks for your support!
 

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YES!! I have those two pins and if I touch them with a metal thing, they do the same thing as if you press the small power button. No where on line anyone states to put the friggin cover back before attempting to power it on. I am not at home at the moment but I will sure try later and let you know. My question is: WHY even put the darn power button on the motherboard when I have to put the cover back on to power it on??

What you did with that "metal thing" on the pins may have achieved the exact same thing as putting the cover back on. So putting the back cover on may not make a difference. BUt certainly try just in case.

Luckily putting the back cover back on is VERY easy (with many Apple computer's it's no so easy). I'm betting that Apple did it this was as a safety measure (either safety for the computer, safety for the human, or both).:) Apple did this sort of thing on other computer models as well over the years.

- Nick
 
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Honestly can i ask a question these boards are so cheap online because of the cap failure wouldn't it be better just to buy one online and replace the board someones got to have one somewhere??
 
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Well I just tried it and no luck. I put the cover back on, tightened the two screws at the bottom, plugged the power cord in, pressed the power button in the back and NADA. The internal power button must be there for a reason. I am assuming it is there for testing/troubleshooting on the original assembly line? So, this brings another question, if it is there, the board should be capable of powering on with the basic attached, video, ram, cpu. Do you think it is worth trying to pull it out and keep the above mentioned components on while trying to power it on?
 

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If you're getting absolutely no "life" when pressing the power button...then I think that you still have a power supply problem.

Many times with a bad logic board, the computer will still power on (fan/fans start, HD spins, LCD lights up)...the computer just won't function properly or boot.

- Nick
 
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Well, it is not that I get no sign of life at all. There is a small heart beat. When I press the power button, LED 2 and LED 3 come on and quickly go off and then there is no sign of life. So power is reaching the board and something is telling me there might be a short somewhere? I read somewhere else that PSU in iMacs (as well as other Apple computers maybe) have a protection system in the 12V power line (when you press power button) that if a short is detected anywhere (video, board, etc.) the power is cut off. For the trickle power there may not be a protection, hence the LED 1 comes on on all iMacs with bad caps and power problem. I am starting to wonder if the caps are still to blame or maybe a bad soldering job. It was very difficult to remove the caps, to clean the occluded holes and solder the new ones in.
 

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I am starting to wonder if the caps are still to blame or maybe a bad soldering job. It was very difficult to remove the caps, to clean the occluded holes and solder the new ones in.

I was going to do this project one time. Paid my $20 for the replacement caps…had all my soldering equipment ready to go…and then decided it was going to be too much of a headache on an older computer. And like you said…always concerned that something could go wrong.

I still have the computer & the replacement caps. Who knows…one day I may still do it.:)

- Nick
 

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Nick, sell him your board and caps! :D

I doubt 3 power supplies are all bad, especially from good sellers on ebay that say they work. i sure would hope not anyway! :D
 
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I was going to do this project one time. Paid my $20 for the replacement caps…had all my soldering equipment ready to go…and then decided it was going to be too much of a headache on an older computer. And like you said…always concerned that something could go wrong.

I still have the computer & the replacement caps. Who knows…one day I may still do it.:)

- Nick

If you have experience with these kind of poorly designed boards, then yes. Otherwise, I would not recommend it to anyone. Too much work and frustration. The money I spent on it is reaching the price of buying another logic board on ebay at this point. I am still going to try to pull it out and power it on just like that. What's the worst it can happen to it? It will still not work so can't get worse than that :). I'll try to snap a high res pic maybe of the solder joints, maybe you guys can see some I can't
 
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Nick, sell him your board and caps! :D

I doubt 3 power supplies are all bad, especially from good sellers on ebay that say they work. i sure would hope not anyway! :D

The original PSU that came with the iMac powers LED #1 but no sign of life when I press the power button. I opened it to look at the caps and they are all flat, no bulging but I understand that doesn't mean they are not bad.

The second PSU, which i purchased from eBay and advertised as "working" powered LED #1 and did the LED#2 & LED#3 quick flashing on and off. However, this PSU was the wrong style and the power connection was off to the middle and did not fit the hole with the back cover. So I returned that one.

The third one was the correct style that matched the back cover. This one also bought on eBay advertised as good "working" conditions. Unfortunately, this one did the same thing as PSU #2 above. I opened it to see of the caps showed any sign of degradation and they looked all good or at least they seemed to be. I understand, it still doesn't mean anything and that I may have had 3 bad lemons on hand but all odds are now pointing to the logic board as you said.

Is there any place online where they can test and repair them? I am not talking about the Genius Bar at the Apple store. They are NOT of us!!
 

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I doubt 3 power supplies are all bad, especially from good sellers on ebay that say they work. i sure would hope not anyway! :D

You're probably right. 3 bad power supplies would seem pretty statistically rare.

- Nick
 

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