[galarneau]

I bought a used G3/500 iMac, and it refuses to boot. I get the startup chime, then a grey screen with an alternating system folder/question mark.

I know that this usually means that the machine can't find the system folder, but the machine also refuses to boot off the cd-rom or off a firewire hard drive (all have appopriate System folders).

I also tried different RAM, with no improvement.

I tried resetting the PRAM, and can boot into OpenFirmware to reset the NVRAM, but no luck.

Is it possible that this machine has a dead logic board? I obtained the service manual, this is the differential diagnosis for a flashing question mark at boot:

1. Check all cable connections to and from the hard drive.
2. Replace the HD/CD/DVD data cable.
3. Replace the hard drive.
4. Replace the hard drive power cable.
5. Replace the logic board.

I've done all of those things except #5 (took the parts from my working iMac). If anyone has any helpfull insight, I'd sure appreciate it.

Somehow the fact that the machine boots and gives me the flashing question mark makes me think that the logic board is good, but maybe not?

[galarneau]

Ok, now it gets weird:

To see if it was the logic board or the power/analog/video board that was the problem, I swapped out the motherboard with one from my often used iMac DV SE 400.

That motherboard worked just fine, and when I swapped the motherboard from the "bad" iMac into my working machine, it started working.

Now, the new iMac works fine back in it's old case, but the old iMac, which I've been using heavily, and I KNOW works well has developed the EXACT same symptoms as the new iMac.

I know I didn't switch the logic boards around (different heatsinks, etc), and I'm actually typing this now on the iMac 500 that wasn't working.

This is so F'ed up.

[Rev-O]

Last time I had a similar issue, I booted my G3 iMac from my iBook. Started iBook in target mode, option + start on the iMac, and it worked like a champ. Unfortunately, it sounds like you're way past this...

[galarneau]

well, got it all sorted out, though I don't know how. Basically kept zapping pram, resetting PMU, etc, and now it will boot off CD or hard drive.

The weird thing is that it would boot off this ONE small hard drive I had, but none of the others, and yes, all the jumpers were set correctly.

From what I can tell, this iMac had a hard life. After pulling off the front plastics, I can see a big crack through the plastic surrounding the screen as if it were dropped. Also, with the screen off, you can see some faint screen burn-in from someone who used OS 9 without a screen saver.

Well, for $86 on eBay, I can't complain. She can live out the rest of her days here in relative comfort until she really kicks the bucket for good.

[nutriskis]

I had the same w/ my iMac G3 700. It was the hard drive. I replaced it with an old 5gb drive I had laying around and it booted right up. I then bought a new 100gb IDE 7200rpm, online for $65. shipped. It was pretty easy to change after I got the bottom of the shell off.

[galarneau]

Yeah, I was worried that it was the hard drive too, but I also couldn't boot off a CD or firewire drive.

I've been working on Macs since 1996, and haven't seen this happen before. I'm doing a little torture testing now to see if it's gonna hold up ok.

I think it must have been corrupted NVRAM or PRAM or something like that.

[discotronic]

Originally posted by galarneau:
Yeah, I was worried that it was the hard drive too, but I also couldn't boot off a CD or firewire drive.

I've been working on Macs since 1996, and haven't seen this happen before. I'm doing a little torture testing now to see if it's gonna hold up ok.

I think it must have been corrupted NVRAM or PRAM or something like that.

If I'm not mistaken, you can't boot from a firewire drive on that model iMac. I could be getting my information crossed and thinking of booting from USB.