Upgrading iMac G3 Motherboard

B

bawalker

Registered
Hello all,

Yesterday when replacing a hard drive in an old G3 350mhz iMac that I have, I pressed the power button on and I got nothing. No boot chime, no display, nothing. After checking the memory and cables were properly connected I tried again, but once more got nothing. The only thing that happened when pressing the power button was that the power light came on and flickered very faintly.

I got online and started reading different forums. I checked everything from the CMOS battery (putting out 3.66v) to the CUDA button, to everything else. In the end it appears either the powersupply or motherboard has went. So I got on ebay and saw a 500mhz G3 iMac motherboard w/power supply. My question is, both the eBay item and my item have the same motherboard model numbers (820-1131-A), but just a different mhz cpu. Am I correct in assuming that because the model numbers are the same then it's safe to upgrade to that motherboard?

Brad
 
hey i dont know much about older macs, but my friend has an original bondi blue imac. sometimes, after fiddling around with it, he'll try to turn it on. nothing happens. however, it usually starts working just fine within a few days. (no idea why this happens!)

if i were you i would wait a couple of days first before buying the part off ebay!:)
 
Well the problem with the iMac is more likely to be the power/analog/video board. I've seen so many of those parts fail and the symptoms you are describing line up perfectly with that problem. Rather than seeking out a new PAV board and going to all the effort of installing it, I would just look for another whole iMac on CraigsList or something local where you can go and check out the machine before buying.

I have several of these machines in my office right now that I've fixed and am trying to sell them for $150.00 each.

In the interest of answering your question directly, yes, the 500 Mhz motherboard will work in your iMac. However, make sure that the new motherboard comes with the bezel (plastic piece) around the ports because the 500 Mhz probably has FireWire and your 350 Mhz probably doesn't -- or if it does, no worries.
 
Thanks for that info. How does one fix the power/analog/video board? Which item is that? While I've got experience with computers, this is my first imac I've pened up and am not sure which part that is.

The 500mhz one does have the plastic bezel that I saw.
 
Well it's sandwiched in the middle of the computer. You have to take out the CRT (screen) and that's a bit of a dangerous process because it can hold a significant charge, even while not on or plugged in. The PAV board is the most difficult component of them all to get at in that computer. For someone who has never done the job before and is following explicit instructions, it will probably take you 2 hours or so to complete the job.

I would not suggest doing it for several reasons -- One: the cost of the part doesn't make it worth fixing. Two: the cost of your time doesn't make it worth it. Three: Due to the age of the case, taking it apart is going to cause some breakage -- the plastic parts have become brittle and are VERY likely to crack or break apart.
 
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