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iMac G3 Bondi Blue with replaced logic board does't boot after chime/bong

M

manmatteo

macrumors newbie
Original poster
Jun 9, 2014
7
16
Hi all! Happy to see a nice PowerPC Mac community here!

I have a Bondi Blue Rev-A iMac (233 Mhz). I had it working with Tiger, but I left it unused for a couple of years (shame on me!). When I picked it up again, the PRAM battery had leaked and severely damaged the logic board. I managed to find a replacement board after a long time, and now I am trying to set it up.

The board didn't come with a PRAM battery, so I bought a new 3.6 V, half-AA battery. Right now the iMac is powering on, and I can hear the boot sound, but the power LED remains orange, and nothing more happens. I tried various combinations of PMU reset, CUDA reset, Command+Option+O+E or +P+R, but none helped.

Any help in troubleshooting more is welcome!!
 
manmatteo said:
Hi all! Happy to see a nice PowerPC Mac community here!

I have a Bondi Blue Rev-A iMac (233 Mhz). I had it working with Tiger, but I left it unused for a couple of years (shame on me!). When I picked it up again, the PRAM battery had leaked and severely damaged the logic board. I managed to find a replacement board after a long time, and now I am trying to set it up.

The board didn't come with a PRAM battery, so I bought a new 3.6 V, half-AA battery. Right now the iMac is powering on, and I can hear the boot sound, but the power LED remains orange, and nothing more happens. I tried various combinations of PMU reset, CUDA reset, Command+Option+O+E or +P+R, but none helped.

Any help in troubleshooting more is welcome!!
Click to expand...

Do you hear a buzzing or hissing sound? Kind of hard to describe...

Does the CRT every turn on?
 
There is a continuous buzzing when I connect it to the power chord. When I power it on, I hear some sort of a "click" from the CRT, but it doesn't actually turn on. After the sound it remains black&turned off, and the LED is orange.
 
manmatteo said:
There is a continuous buzzing when I connect it to the power chord. When I power it on, I hear some sort of a "click" from the CRT, but it doesn't actually turn on. After the sound it remains black&turned off, and the LED is orange.
Click to expand...

Sounds to me like a blown PAV board.
 
I don't actually know which part the PAV board is, but wouldn't its failure prevent completely the mac from powering on? I do even get the boot sound, and I can hear the disk doing a startup check - if I try to remove the CPU board, I obviously don't hear the sound and the hard disk spins plainly.
 
manmatteo said:
I don't actually know which part the PAV board is, but wouldn't its failure prevent completely the mac from powering on? I do even get the boot sound, and I can hear the disk doing a startup check - if I try to remove the CPU board, I obviously don't hear the sound and the hard disk spins plainly.
Click to expand...

It is normally indicated by weird sounds not coming from the CRT or hard drive. Remember the iMacs are fanless so you won't hear them running.
 
IIRC, the way to test this is to disconnect the video cable from the motherboard and attach an external monitor. It should boot with the monitor.
 
jruschme said:
IIRC, the way to test this is to disconnect the video cable from the motherboard and attach an external monitor. It should boot with the monitor.
Click to expand...

I definitely need to try this. I read that some people had similar symptoms, and the problem was in the flyback transformer for the CRT. However, I don't have an Apple-to-VGA adapter... do you know if there is a quick-and-dirty way around this?
 
This is a tray loading iMac, they have a fan and are a completely different design than slot loading iMacs. The PAV board is one of the two board to either side of the CRT. There are two different versions of it for tray loading iMacs. Make sure you get the correct one if you replace it.
 
Intell said:
This is a tray loading iMac, they have a fan and are a completely different design than slot loading iMacs. The PAV board is one of the two board to either side of the CRT. There are two different versions of it for tray loading iMacs. Make sure you get the correct one if you replace it.
Click to expand...

Was it the tray loader PAV boards that had the switch on one of the types?
 
manmatteo said:
I don't actually know which part the PAV board is, but wouldn't its failure prevent completely the mac from powering on? I do even get the boot sound, and I can hear the disk doing a startup check - if I try to remove the CPU board, I obviously don't hear the sound and the hard disk spins plainly.
Click to expand...

The PAV board is the Power, Audio, and Video board. They are a real common problem on iMac G3s and the only solution is to replace. Depending on the defect, you may be able to get a electronics guru to rebuild the board depending on what went wrong.
 
I will try to get some more informations on PAV board failures. What is the switch you are referring to? Is it something useful to me?

Altemose said:
Was it the tray loader PAV boards that had the switch on one of the types?
Click to expand...
 
manmatteo said:
I will try to get some more informations on PAV board failures. What is the switch you are referring to? Is it something useful to me?
Click to expand...

The switch is there IIRC to switch between different CRT manufacturers in the iMacs at the time. I think one CRT was made by LG while others were by a foreign company Hon Hai. The PAV boards made by Apple sometimes have this switch.
 
Thank you very much for the help so far. I have made a little step forward: connecting the original keyboard, I am able to correctly perform a PRAM reset (via Command-Option-P-R), and I can hear the machine rebooting and chiming a second time. So i would assume that the "computer" part of the iMac is OK.

Do you have any clue on what could the reason why the LED doesn't turn green? Is it related to the CRT? If it could also be related to a bad logic board-CRT link, it could still be because of the battery spill I had in the beginning.

One last thing: is this the notorious PAV board?
https://docs.google.com/file/d/0ByiN9SreZpt7SlZyQzlta3BfRVBTQmh4ZVduZmUzbkVJSkhN

If it is, I might get one for cheap provided I can be sure that the problem lies there. If the problem is in the CRT flyback transformer, I guess I can loose my hopes...
 
The amber LED and startup chime points to a video problem. Reseat all of the video cables, VRAM, CPU card, and RAM. If you want to replace the power supply board, you want part number 661-2081.
 
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