fixing dead imac g4

000Jon000

macrumors newbie
Original poster
Jul 21, 2017
6
0
Adelaide, Australia
17" iMac G4, GeForce 4 MX, 1GHz, 256MB

Hi everyone,
This imac was last powered on 6 months ago, it now makes no response to pressing power button at all. Here is what I tried: Replaced PRAM battery, reset PRAM by pressing the button, Hold power for 10 sec and plug back in, plug in and power at same time, resat the ram modules, tested diagnostic solder points and got 3.6V for battery, 12.20V for 12V, got 0.01V for 12VLSP and 5V. PSU was tested with multi-meter using the service manual guide and passed the test. I noticed some white and dry stuff around C241 on the logic board (next to 16 pin power connector) that needed to be rubbed off with alcohol.
What should I do now?
 

amagichnich

macrumors 6502
Feb 3, 2017
477
286
Stuttgart, Germany
My second eMac wouldn't turn on too. It was a faulty power button. I built myself a testing power circuit and found that the button does nothing. Then started the eMac with a short circuit like all my old window PCs with a wire on the power button pins. That would be an easy to fix problem
 

000Jon000

macrumors newbie
Original poster
Jul 21, 2017
6
0
Adelaide, Australia
My second eMac wouldn't turn on too. It was a faulty power button. I built myself a testing power circuit and found that the button does nothing. Then started the eMac with a short circuit like all my old window PCs with a wire on the power button pins. That would be an easy to fix problem
Thanks, ill try that right now
 

000Jon000

macrumors newbie
Original poster
Jul 21, 2017
6
0
Adelaide, Australia
Here is some pictures, first one is where the white powder was, second one is of where the power switch used to be. Unfortunately the improvised power button didn't work, any other suggestions on what to do? If it still doesn't work, ill just turn it into a PC with an Intel compute stick inside.
 

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000Jon000

macrumors newbie
Original poster
Jul 21, 2017
6
0
Adelaide, Australia
Do you have another PSU to try? it sounds like a PSU issue

IIRC iMac G4s did have a few PSU issues
I tested the cable and the supply, got 245V at the end of cable, 12.20V on all connectors and 12.20V for diagnostic test point on logic board, 5V didn't show around 5V, it was at 0.010V, could that still be the PSU?

Next thing ill try is putting 5V through the Molex connector to see what happens.
 
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