iMac G4/800 15" - White Screen at Boot

[John8520]

I happened across a very reasonably priced iMac G4 today and decided I just couldn't turn it down. It's a 15" 800MHz model, one that can actually run OS9, which I find very appealing. The machine is very clean outside and only had minimal dust inside. The owner didn't know anything about it and had no peripherals or accessories. It was upgraded with a single stick pf 512MB PC133, but the 60GB HDD and combo drive are stock. No airport card or SODIMM RAM installed. 

While it does boot, the only video I get is flat white. Cmd-Opt-P-R resets the PRAM (at least, I can hear it reboot multiple times) but I cannot (visually) enter either open firmware or the option boot menu. Some cursory googling has suggested this may be a hard drive problem (which makes no sense to me?) but I put the drive in one of my G4 towers and it works perfectly - it even has a fresh install of 9.2.2 on it, so it should boot in the iMac.

I have replaced the PRAM battery with a known good one, and have swapped in RAM from one of my G4s but it seems to make no difference. I've also tried leaving it on the white screen for a while but nothing seems to happen. When I leave the drive in it sounds like its booting, with some drive activity. Unfortunately I do not have a mini-VGA adapter at hand to test video out with.

Any suggestions?

 

[IlikeTech]

Broken or disconnected video cable?  Open it anyway to remove PRAM battery

 

[John8520]

Video cable is connected just fine, have reseated it several times. Video doesn't change when the cable is wiggled. Have already replaced the PRAM battery with a known good one, no change.

 

[John8520]

No progress yet in troubleshooting but I have ordered a Mini-VGA adapter, hopefully that helps. Searching around it seems like a lot of people fix this issue with a new hard drive - I have a new old stock 120GB IDE drive coming tuesday that was going to be for another machine but I think it'll go into this one to see if it gets me any further. 

I put the optical drive, a superdrive, into my Digital Audio as well and it reads CDs just fine, but I get errors when burning. Right now I have only tested one type of CD-R so that may be a coincidence, or bad media. The iMac does the same thing even if no IDE cable is connected at all, so I have a bad feeling that this hard drive thing isn't going to make any difference. I'm going to hunt around for another optical drive to slap in there as well.

 

[John8520]

No progress yet in troubleshooting but I have ordered a Mini-VGA adapter, hopefully that helps. Searching around it seems like a lot of people fix this issue with a new hard drive - I have a new old stock 120GB IDE drive coming tuesday that was going to be for another machine but I think it'll go into this one to see if it gets me any further. 

I put the optical drive, a superdrive, into my Digital Audio as well and it reads CDs just fine, but I get errors when burning. Right now I have only tested one type of CD-R so that may be a coincidence, or bad media. The iMac does the same thing even if no IDE cable is connected at all, so I have a bad feeling that this hard drive thing isn't going to make any difference. I'm going to hunt around for another optical drive to slap in there as well.

EDIT - another interesting note: as soon as I boot it up the CPU is BLAZING hot. I have the HDD/CD carrier out at the moment, and when I manually open the CD door I can reach in and feel that the CPU heat pipe is right under the slot, so I can easily touch it. Within a minute of booting I can feel that the heatpipe and spreader on the CPU itself are incredibly hot. I put fresh thermal paste on the junction between the pipe and the body of the machine, but I think I need to replace it on the actual CPU itself. That said, I do know that the machine is at least somewhat operational - I can get into open firmware and "reset-all" and "power off" both work as expected (restarting and shutting down the machine, respectively).