Ga door naar hoofdinhoud

15 inch "Desk Lamp" iMac G4 700MHz M6498 PowerMac 4,2

32 Vragen Bekijk alle

iMac g4 won't boot up and weird screen when it cans

Block Image

Block Image

Hello, recently a school gave me an imac g4 that was used for educational purpose and the school said that the mac was dead. So i first pluuged the power outlet and it booted but with a weird screen changing to completely white. A few weeks ago and yesterday, i just replugged it to test the mac but now, the mac won’t boot up, no fan nothing. Only a fast clicking sound coming from the power supply that stops sometimes after a few seconds. I dissasembled all the imac and look for any damage on the mac. With a multimeter i checked the voltage coming from the first power supply board and i got 400 v continue but on the second board, i have no voltage. Have you got any tips to look for maybe shorted parts or capacitors that usually break up in these machines ? Thanks for help

Beantwoord deze vraag Dit probleem heb ik ook

Is dit een goede vraag?

Score 0
Voeg een opmerking toe

1 Antwoord

Het nuttigste antwoord

G’Day Correia ;

You are on the right track , HOWEVER , to be really successful one should purchase a decent ESR meter to check any electrolytic caps in the power supplies .

An ESR tool (Effective Series Resistance , I could be wrong , been a long time for that definition ) will test capacitors ‘in circuit’ . No need to de-solder . HOWEVER there can be a gang of caps in parallel and some meters will give a pass . If any have swollen tops or stuff leaking they are bad FOR sure . If any are in a parallel gang I would swap them all . Hope you have a heavy duty motorized solder sucker to get caps out of multi layer boards ( heat from most hand irons will get pulled away into large copper ground planes )

Sorry I have not had any G4 experience , but Apple makes such good quality I doubt caps are bad , but , I have done so many other devices and brands that I would not be surprised .

That ‘clicking’ you mention could now be a shorted MOSFET causing switching power supply to constant reboot . Use DVM on semiconductor junction test to look for bad power MOSFET or transistors .

Less likely is you are hearing the hard drive smacking the heads against the frame . Shed the hard disk for boot test maybe .

Just some thoughts , Good luck

Hugh

Was dit antwoord nuttig?

Score 1

7 opmerkingen:

Ok, i will check that. The clicking sound comes from the first power supply (hot part) so i will look for mosfets. Thanks for your answer :)

door

Hello, i saw on YouTube that on these models, people were using an hair dryer to boot their mac and this worked for my mac but i can’t find the component that react to heat :/

door

ahoy there...sure sounds like a bad cap to me . quite often many restart attempts will warm up a flaky capacitor's inards and device will start . Beg or borrow an ESR meter maybe ?

Luck

Hugh

door

Hi, i just changed the three capacitors and now it works ! But the problem is that i have weird multicolor lines on the screen i don’t know if the lcd is dead or the gpu

door

I posted above pictures of the problem

door

2 commentaren meer tonen

Voeg een opmerking toe

Voeg je antwoord toe

Correia zal eeuwig dankbaar zijn.
Weergavestatistieken:

Afgelopen 24 uren: 0

Afgelopen 7 dagen: 2

Afgelopen 30 dagen: 3

Altijd: 97