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Apple Desktops Discussion of Apple's desktop machines including Mac Pro, iMac, Power Mac, and mini

iMac - New to mac and have problem with dead G3 imac


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acharris05

 
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Hi all I am new so be gentle, today I took a chance and picked up a G3 Imac with 400 mhz processor for 5 gbp. Guy said it was working and when I brought it home and plugged in, I get nothing no LED on the power switch lit and no response from the switch.

I took it apart to have a look and at first I thought the switch might be faulty, so did away the switch on the front panel and used the small button on the power switch PCB with the LED. Still no boot.

I assume that there should be some standby light on the Imac when I turn on at the mains. then spring into life when pressed. I am assuming that it is a power problem, as when I switch on the mains, I get a little crackle sound on the capacitors by the power board like electricity is going to it for a split second.

Any help, as I got it so I could have a play around with the mac without spending a lot of money, but I guess I werent that lucky with my chance. Any help appreciated. Thanks.

Anthony
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Mac SK

 
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Theres a power switch on the imac key board too. If the pram battery is dead you can get that crackel sound and no start up, But you get the same if the back loop transformer is bad, so replace the battery and see what happens.
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acharris05

 
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Hi, I checked the voltage on the battery and it is showing as 0.10, so I am assuming that the battery is dead. 2nd, I measured the voltage on the trickle 5v and I am only getting 1.31v and when I checked the DCO I get a reading of -0.81v (which the guide says between -1.21 and + 1v and the reading is right).

So does this sound like there is voltage and the PAV board (i think that is right) is OK. Thanks in advance.

Also I have not got a mac keyboard, only a PC one.

Anthony
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louishen

 
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Mine died a year ago, the light on the power switch would come on then fade away. A new battery fixed the problem, as as they are not expensive, replace the battery first
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acharris05

 
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Hi all, I got the PRAM battery and replaced and then I did the resetting of the PMU chip and the Imac is still the same. The only crackle sound I get seems to come from the coils on the mobo when I turn on at the mains.

I got 3.63v on the battery
I get -0.81v on the DCO board
but I only get 1.31v on the 5v trickle voltage

Am I right in assuming that the 5v trickle voltage should read around the 5v. Should I check the fuse to see if that it OK. Thanks.

Anthony
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Mac SK

 
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If the button lites for a second or so the fuse is allright. You know if the firmwear is messed up the machine will not start. The firmwear lives on the hard drive. Has anyone replaced the drive or upgraded the os from 9 to 10 with out installing the correct firmwear update for OS10. Its called death by ten. The unix code burns up the video chip. Take out the hard drive and see if it fires up and you get the flashing ?
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