Black screen upon 840 AV bootup

[habibrobert]

Hi everyone,

i have a Quadra 840 AV board that has been recapped and worked in the past. Recently it's been giving me some trouble. When I turned on the motherboard, I saw that the boot screen came up as expected. When I restarted the thing, all I got was a black screen...no boot up screen...nothing. After multiple restarts, I'm starting to get a little worried that something has happened to it. I know these 840 AV board are notorious for being finicky and having really bad capacitor leaks, but since it has been recapped, I see how the latter could be a problem in this case. Also, I know its not the power supply as that was also recapped. 

In the past I've read about a few people on here that have been brave enough to try and repair/troubleshoot 840 AV boards. I was wondering if there is anyone out there that can help me out? I'm afraid I've done everything I can think of to get this thing to work again, including changing the ram sticks. I think expert hands are needed in this case. Please let me know if you are able to help out.

Thanks very much! 

 

[Unknown_K]

Reseat the VRAM. Does it still bong? Use a Nubus video card for testing.

 

[habibrobert]

Reseat the VRAM. Does it still bong? Use a Nubus video card for testing.

I tried reseating the VRAM, but I didn't hear any bong. I don't have a video card that would work with a 68k, I'll see if I can get one from somewhere. I have a schematic for the board, but honestly I have very little experience with reading schematics. 

 

[beachycove]

Could be a dead hard drive.

 

[habibrobert]

Could be a dead hard drive.

If it were a dead hard drive, wouldn't it still boot up? It would just give the question-mark sign when there is no hard drive. Right?

 

[beachycove]

Termination problems can lead to the symptoms described, sometimes, and I have seen it too with a HD that had a blown component. Black screen were us.

I suppose I would suggest simply that you strip everything back to one known-working, terminated hard drive (no cd) and see whether the machine then boots to something recognizable. It is now the HD that is likely to be the weakest component, so I'd begin there.

This may also be of some use: http://members.tripod.com/thecomputerguy__/startup_p.htm .