Imac g3 refusing to do anything

Honk-ie

New Tinkerer
Aug 25, 2025
7
2
3
I recently picked a imac g3 and when I originally bought it, it would beep 4 times and then do nothing. I did some research and found that it means that the hard drive could be corrupted or damaged. So, I replaced the hard drive (even if it worked, the storage space was very small and I would have replaced it anyways) and then after that, it wouldn't even turn on! so I replaced the PRAM battery, and now im back to square one. I've tried all the key combinations to boot off of a cd and to get it to go to the boot selector, but nothing has worked. Is the logic board cooked? I am using a original imac software install disk. Im at wits end, I dont know where to go. Any help is appreciated.
 

phunguss

Active Tinkerer
Dec 24, 2023
434
374
63
Stillwater, MN
1. Does it power on now without the 4 beeps? Screen comes on? Do you hear the Apple chime? Yes to all, ok, no to all, recheck your internal connections.

2. You cannot boot off cd, you just get the question mark folder? - Check your hard drive cable. Make sure the replacement hard drive is correct master/slave setting.
 

Honk-ie

New Tinkerer
Aug 25, 2025
7
2
3
1. Does it power on now without the 4 beeps? Screen comes on? Do you hear the Apple chime? Yes to all, ok, no to all, recheck your internal connections.

2. You cannot boot off cd, you just get the question mark folder? - Check your hard drive cable. Make sure the replacement hard drive is correct master/slave setting.
The screen does not power on at all, but the cd drive will spin up and I the hard drive will spin up too. I checked before I put the hard drive in that it was in master/single. Theres no apple chime at all. Im 99% sure that the internal connections are all good, but I could be wrong. Could the firmware be corrupted? Here is a video of what happens when I turn it on and try to boot from cd.
 
Last edited:

phunguss

Active Tinkerer
Dec 24, 2023
434
374
63
Stillwater, MN
Have you used the iFixIt guides for your disassembly or did you just wing it?

I would disassemble and verify you have made all connections. The tray loader should have a 15pin video cable, and two other power connectors that drive the motherboard and the monitor (make sure they are is plugged in all the way, it has a snap clip). See iFixIt photo

Do you have any other Apple vintage devices (DB15 to VGA adapter, you could try an external monitor)?
 

Honk-ie

New Tinkerer
Aug 25, 2025
7
2
3
Have you used the iFixIt guides for your disassembly or did you just wing it?

I would disassemble and verify you have made all connections. The tray loader should have a 15pin video cable, and two other power connectors that drive the motherboard and the monitor (make sure they are is plugged in all the way, it has a snap clip). See iFixIt photo

Do you have any other Apple vintage devices (DB15 to VGA adapter, you could try an external monitor)?
I used a ifixit guide to replace the hard drive. I could try finding a DB15 adapter, and plugging it into a different display, but I'm sure that all of the internal cables are plugged in. The CRT could be dead, the computer was sitting for a while in a garage, but I have no way to test it. Maybe the firmware on the board is corrupted in some way? (I also fixed the video btw)
 
Last edited:

phunguss

Active Tinkerer
Dec 24, 2023
434
374
63
Stillwater, MN
The video shows you are still getting the 4 beeps. Try disconnecting the hard drive and only leave the cdrom attached. When you power up, hold down Command-Option-R-P and see if you get other sounds (cycle through 3 boot chimes to fully reset everything).
 

Honk-ie

New Tinkerer
Aug 25, 2025
7
2
3
The video shows you are still getting the 4 beeps. Try disconnecting the hard drive and only leave the cdrom attached. When you power up, hold down Command-Option-R-P and see if you get other sounds (cycle through 3 boot chimes to fully reset everything).
Alright, ill try that.
 

Honk-ie

New Tinkerer
Aug 25, 2025
7
2
3
The video shows you are still getting the 4 beeps. Try disconnecting the hard drive and only leave the cdrom attached. When you power up, hold down Command-Option-R-P and see if you get other sounds (cycle through 3 boot chimes to fully reset everything).

Should I try disconnecting the ide cable and try the test again, or would it not make a difference?
 
Last edited:

Honk-ie

New Tinkerer
Aug 25, 2025
7
2
3
So this Apple thread says the boot ROM it toast.

"Four beeps. Indicates there’s a bad checksum for the remainder of the Boot ROM. (Checksum refers to a method of determining whether data is corrupt.)"

No idea if that is fixable... otherwise snag a cheap mobo on eBay (this is the only one I saw today).
Oof, thanks for the help though. I was close to just throwing it out, thanks for all the help! 👍