imac g4 20 inch 1.25ghz DOESNT BOOT UP

Question

imac g4 20 inch 1.25ghz DOESNT BOOT UP

Ok, so.. ive just bought a second hand imac g4 20 inch 1.25ghz..

When the person i had bought it from had it, it was working, started up fine..

However ive just received it today, and it wont turn on.

Ive put the power cord in, and i can hear a quiet squeeking noise coming from the computer.. but when i press the power button, nothing happens..

Any ideas what the issue might be?

or even better... anything i could do to try and get it working again?

iMac g4 20 Inch 1.25ghz, Mac OS X (10.3.x)

Posted on Jun 16, 2010 3:42 AM

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Answer 1

Jun 16, 2010 3:45 AM in response to Mickyponthenet

also, the seller noted that the power button may be tempermental.. he said it may needed to be pressed 5 - 10 times before the imac will turn on..

Ive already tried pressing it a few hundred times already, and still nothing

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Answer 2

mrtotes

Level 6

11,836 points

Jun 16, 2010 1:51 PM in response to Mickyponthenet

Awesome iMac.

If the seller is correct then it may require some fiddling on the power button, i.e. the physical button/metal 'spring' may not be connecting with the actual electrical switch. Here's a picture from my iMac G4:

Click to embiggen.

The other thing you could try is resetting the Power Management Unit (PMU). Please read the instructions carefully!

http://support.apple.com/kb/ht1712

If the PMU doesn't work let us know.

regards

mrtotes

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Answer 3

Jun 16, 2010 4:05 PM in response to mrtotes

I havent got the screw driver to undo to get to the switch spring...

So i went and tried the PMU switch, and ive had no luck..

To get to the factory only parts on the imac, i need a Torx T15 screwdriver, right?

And thanks so much for the help, your a godsend

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Answer 4

Jun 17, 2010 5:05 AM in response to mrtotes

Ive now been told, that since he had a power cut ages ago, its had that problem...

So im suspecting its had damage due to a power surge or a simelar problem..

I opened the iMac today and checked the switch, nothing seemed out of the ordinary..

The Seller has offered me a full refund, but im wondering whether i should just send it off to someone to repair it properly, or whether its completely screwed up and i should accept the refund?

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Answer 5

spudnuty

Level 5

7,122 points

Jun 17, 2010 7:03 AM in response to Mickyponthenet

Hey Micky,

Ive put the power cord in, and i can hear a quiet squeeking noise coming from the computer

That could be indicative of a power supply problem. Unfortunately the 20" has a totally different power supply:
"922-5796 (15" & 17")
922-3104 (20")"
These are internal Apple numbers and I have found no way to cross reference them.

since he had a power cut ages ago, its had that problem

Yup that could have damaged the power supply or the PMU.
It's hard to say what to do.
On the one hand as mrtotes says it's an "Awesome iMac.". I've been keeping my eye out for one for years.
So:
What was the original cost?
Are there even parts available given the rarity of the 20"?
What would the repair cost?
If it were me the desire to have a 20" iMac G4 would most likely overcome any practical concerns. I would go for an adjusted price and look for a power supply. It's possible someone has worked out a hack for an ATX to run this machine. I use one to test G5 iMacs since they have so many bad power supplies.
Richard

Message was edited by: spudnuty

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Answer 6

Jun 19, 2010 6:14 AM in response to spudnuty

Hey Spudnutty..

Ive actually got it turning on now (it may well be that the power supply was damaged, i dont know)

Basically.. what the seller told me was true.. ive pressed the power button alot, and it started up

Im even writing this post on this iMac right now..

Ive just come across another problem now,

and thats the fan being loud constantly..

I guess im going to be replacing the 1/2 AA battery inside the iMac to see if that fixes the tempermental switch completely..

And now its just on to the fan issue..

Im running Mac OSX 10.3 and ive searched for alot of fan control software, and ive found nothing for an imac running 10.3..

Ive cleaned it out too and prodded a few things, and nothing seems to have cured it..

but other than that, this issue is "Fixed".. until i can find a way to COMPLETELY fix this switch

Thanks for the help guys

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Answer 7

Jun 19, 2010 6:15 AM in response to Mickyponthenet

Its now booting up... As the seller said, it needed to be pressed alot of times before itll start up..

I dont know exactly why this is, but ill be replacing the internal battery and maybe having a look at replacing the power supply.

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Answer 8

Jul 19, 2010 9:53 PM in response to Mickyponthenet

I am bumping this thread because I have the same problem. My iMac g4 20 stopped working after I moved it to another room. The PSU emits a ticking sounds when the computer is plugged in. It also produces current but the mac won't start. I have ran some test with the PSU of an iMac g4 17 and I get the chimes but the screen stays off. So basically the logic board is fine. It is just that the PSU cannot sustain the load. I have had this happening on an iMac G5 I worked on for a friend. Anyway PSU for iMAc 20 are hard to come by under $150 and I though somebody may have experience working on the PSU itself.

Contrary to what I have read in different places 17" PSU are not compatible with the 20" model. I am pretty sure the inverter current is 24V on the 20" and 12V on the 17". On my non functioning PSU there is a green wire coming from the board with 24V written on it and a multimeter gives me a 24V reading. The same wire on a 17" gives me a 12V reading.

If you are familiar with these PSU you may know that they are split in 2 sections/stages that fit on each side of the dome. I belive one is the AC/DC stage. I measured and it gave me an output reading of 300V DC and seem to work fine. The second stage is the one reducing voltage to the different level needed 24V, 12V and probably 5V too. It is the one that is ticking yet producing voltage but not enough current to start the computer. Does anybody know what component could produce a ticking sound on a PSU? Anybody has schematics of these PSU?

If it would have been any other mac I would have given up but I love this machine too much and I am not ready to let it go. I was using it daily for PhD writing, email and such.

Thanks in advance

Greg

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