View Full Version : 840av to 8500 upgrade problem

05-21-2001, 02:26 AM

I finally scrounged up enough parts (i think) to upgrade my trusty 840av to an 8500 power mac. I have the 8500 logic board, a 150 mhz processer board, and the 8500 rear panel. I thought this would be all that was required, maybe I'm wrong.
The 8500 logic board is used, and came with 32 megs memory, and a cache chip, but that's all. After putting all the pieces and parts together, I tried to boot the computer, but I get no start up chime, and the monitor stays dark. The hard drive spins up, and the power on LED lights up, but nothing else. Am I missing something??
The 8500 MB did not come with a ROM chip (which I think I need, right?), so I took one out of a 6xxx something MB that I had laying around. It plugged in, but is too large. I also changed the battery with a fresh one, but it didnt make any difference. Can anyone lead me in the right direction with this upgrade, as I don't know what to try next.

Thank you in advance...Brian

05-21-2001, 04:41 AM
pull that ROM, please. It is not needed.

i would test the power supply, and swap daughtercards.

make sure everything is well -seated.

pull the cache, just for now.

you can work with just one DIMM installed at the outset, until you get things rolling.

05-21-2001, 11:56 AM
Does the 840AV power supply have the connector for 3.3V supply? Without 3.3V the machine won't work right. However, a PPC604/150 should boot without 3.3V, your PCI slots just won't work. Hmmm. A PPC604e or G3 will give just the symptoms you have without 3.3V. I haven't tested this issue extensively, but I do know that you need the power supply to put out a 3.3V supply (in addition ot the traditional 5, 12, -5, -12) in order for the 8500 to work properly.

05-21-2001, 04:01 PM
Hi again;

Thanks for the help so far. I pulled the ROM, cache, and one DIMM, but these changes made no difference. I haven't checked the output of the power supply, yet, but it was working fine in the 840av, so I assume it is alright. I only have the one daughter card at the moment, so I haven't swapped it, yet.
I checked with the supplier of the 150 mhz card I have, and it is a 604e card, then I checked the label on the power supply, and don't see an output of 3.3 volts listed. Maybe I should pick up an 8500 power supply, and try again, huh.
I'll post back as soon as I locate one with the results. My thanks so far for everyone's help.


05-29-2001, 03:00 AM
It?ll probably work when he gets the Power supply. Apple sez the 840AV & 8100 power supplies were interchangeable, but differed for the 8500 model. Specifically "NOT backwards compatible" is their terminology, even though it might physically fit. Darn, I was hoping to upgrade my 8100 at some stage...