imac g4 - indetifying a problem?

3 replies [Last post]
Joined: Nov 23 2005
Posts: 7

Hi there people. I have a broken imac g4 which i got my hands on and i been messing about with it.

The problem i have is that when i turn on the imac the fan spins, the cpu heatsink gets warm and the psu makes a buzzing sound. however there is no bong sound from the speakers, hdd and cd rom do not spin or open, no picture on the external monitor (external monitor cos the previous owern snapped the tmds connection of the board.) and no noise from the internal speaker.

Any one got any ideas on how to go about tackeling to see if its completely buggered.


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iantm's picture
Joined: Apr 2 2005
Posts: 709
Logic board

Those are symptoms of logic board failure. What you are experiencing is the result of the unit failing POST for some reason very very early on. Have you tried resetting the PMU? Resetting it may help.

- iantm


- iantm
ACPT & ACDT (long expired)
BMW Certified Technician

dankephoto's picture
Joined: Dec 20 2003
Posts: 1900
try resetting the PMU

I read this somewhere . . . ;D

Resetting the PMU on the Logic Board
Resetting the PMU (Power Management Unit) on the logic board can resolve many system problems. Whenever you have a unit that fails to power up, you should follow this procedure before replacing any modules.
1. Disconnect the power cord.
2 Remove the user access panel from the bottom of the computer.
3 Press the PMU reset switch (shown below) once on the bottom side of the logic board and then proceed to step 3. Do NOT press the PMU reset switch a second time because it could crash the PMU chip.
4 WAIT ten seconds before connecting the power cord and powering the computer on. If the computer powers on, go to the next step. If the computer does not power on, there is something else wrong with the computer, refer to the symptom/cure, “No Power


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Joined: Dec 20 2003
Posts: 851
If the power supply is making

If the power supply is making a buzzing sound, remove it and inspect it for broken solder joints. Reflow any joint that looks cracked, broken, or discolored.


Dr. Bob
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