4016 Views 9 Replies Latest reply: Jan 7, 2011 4:08 AM by dave2889
The PRAM battery is a good and cheap place to start. The computer could simply be forgetting the last geometry settings. You can, with care and a non-conductive grasping device, reach the PRAM battery through the RAM door. If that doesn't work, you'll need to pull the case bottom.
That's the good news. If a battery doesn't fix it, then you probably are looking at video problems that are hard to overcome. The slot-loading iMacs with only passive, convective cooling seem to be killing off their PAV (power/analog/video) boards from heat at an alarming rate. Ours took a nosedive after installing OSX and a bigger hard drive. The boards available are all used so it's unlikely you can get one that hasn't been "in the oven."
If you can find a dealer in Australia that carries this (made in France) SAFT 3.6-volt battery (shown here), it's a better one - having 25% more life (1,200 mAh compared to 900 mAh). Otherwise, the battery that you've found is suitable for your iMac. While a weak/dead battery will often cause a blank screen at startup, I don't think it will cause screen anomalies. That sounds more like it's related to the PAV board or the CRT's circuitry itself. Do you also disconnect the iMac from electrical power, after shutting it down? This causes the internal battery to preserve the PRAM settings while disconnected, which ultimately shortens the battery's life.
I found my old voltmeter, and decided to measure the battery's voltage, it only measures 27 millivolt. Didn't even think they could get that low. I haven't bought a replacement yet, will do eventually. In the meantime, I bought a Power Mac G4 "SawTooth" G4/350 off eBay to play around with. Might also buy a spare battery for that too.
as it emits a very high pitched whine after it's turned off
Hmm that sounds like a flyback problem. There's wires in those smaller than a human hair so they go bad a lot.
Around Chicago the iMac G3s are so plentiful and cheap that my repair philosophy was to find a running cheap one (usually less that $10 or more likely free) and swap faster logic boards into it. (500 or 700).
I used to replace those flybacks but it's a pain and more than the cost of a used one.
Replacing the flyback is not something I'd want to attempt. I'm not risking electrocution. Should I just scrap it now, or keep it until it actually dies? Eventually I'll want the RAM and hard drive for the PowerMac I mentioned earlier, and once that Mac arrives, I won't need the iMac. As mentioned before, it's suspected it also has PAV board problems, so probably isn't long for this world anyway. Only paid AU$15 for it at the local flea market, so not much of a loss.
Replacing the flyback is not something I'd want to attempt. I'm not risking electrocution.
Good idea but really not much of a danger if you understand what you're doing. I don't do it anymore since it's a massive pain and the part is no longer available.
I have an iMac DV SE 500 MHz (2000), which works OK, but the screen picture moves most of the time I shut it down or restart. I have to use the screen positioning control panel to fix it. I'm using OS 10.4.11
So like you say a PAV board problem (of which the flyback is a part). Looks like the horizontal size is shrinking:
Notice the two black bars on the side, they weren't there before I restarted
Eventually I'll want the RAM and hard drive for the PowerMac
both would work in that 350 G4. I'm personally on a MDD G4 dual 1.2 GHz machine. My ol' work horse!
When the iMac G3 finally dies I'd pull the logic board and mass store in case you run across a working 350 - 400 iMac G3. It's easy to swap that board into either.
Instructions can be found here:
(You might see some other goodies there)
Message was edited by: spudnuty