iMac G4 1.25Ghz 17" Problem

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Joined: May 25 2009
Posts: 3

I have a 2003 iMac G4 1,25Ghz 17".

It runs fine and I have not had any problems except 
this annoying issue - it takes several attempts to get 
it to start-up.

For example, first thing in the morning, I press the 
power button and it locks at the white screen with the 
grey apple logo with faint grey or white vertical lines.
I repeat restarting the iMac with the power button and 
it happens three or so times and usually boots up fine 
to the Desktop on the third or fourth attempt. After 
that it runs fine.

I have changed the internal HDD as it was failing with 
a new unit, upgraded the RAM, changed the PRAM 
Battery, zapped the PRAM and PMU, repaired disk 
permissions and even tried a clean install of the OS.
In addition, I had a look at the logic board and all the 
capacitors looked fine and all connectors were in. It 
has lead me to think it may be the PSU that is on its 
way out? System diagnosis is fine, RAM is OK and 
there are no common symptoms of bad capacitors on 
the logic board like freezing, crashing and graphic 
artifacts on screen.

I do not have the Install discs that came with the computer and I believe the Apple Hardware Test (AHT) is on disk one, only the five Software Restore discs. The iMac has Leopard 10.5.7 on and is all up to date. The Apple Support site does not have this specific model AHT for download unfortunately.

The previous owner (first owner) said he never had any problems 
but admitted the iMac was rarely turned off - it would 
go to sleep when it was not being used.

I would be most grateful if anyone could throw some 
light on this or share similar experiences before I start 
spending money on replacement parts in the hope it 
may fix the issue.

For the last 72 hours the iMac has been left on (it sleeps while I do) and I have had absolutely no problems with it. It powers back on from sleep without fail.

Thanks in advance.

Iain

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Offline
Joined: May 25 2009
Posts: 3
Please can anyone help?

Please can anyone help?

cwsmith's picture
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Joined: Oct 13 2005
Posts: 699
2 questions

Did you change the PRAM battery while you were inside?

Did you clean the thermal contact points and apply new thermal paste? (Please say yes)

PSU is certainly a possibility, but the PRAM battery is easier and cheaper to replace first.

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Offline
Joined: May 25 2009
Posts: 3
Hi. Yes - changed the PRAM

Hi.

Yes - changed the PRAM battery with a new 3.6V one. Applied Zalman thermal paste after removing old paste.

Funnily enough, I was away for two nights so switched off the iMac and when I came back and turned it on, it booted to the desktop, no problem.

There is something temperamental...... could be the PSU. Maybe someone could explain to me how a PSU works at start-up?

Could it be bad start-up circuitry on the logic board? Having said that, once on the iMac runs beautifully.

I contacted Apple a few days ago and they are sending me the correct AHT disc for my machine so I will report back anything that comes up.

Cheers.

Iain