Yodd
Member
Hola folks!
I recently received a new to me Quadra 700. It was sold as not booting.
While it does power on (power led is on), there is no chime (I do hear a click/pop from the speaker) and no video. While the scsi drive spins up, it doesn't boot from it as far as I can tell.
Motherboard is squeaky clean with barely even a trace of dust. For a 30 year old machine, it doesn't look old at all. It almost looks like new old stock. Zero battery leakage as the previous owner pulled the battery out a decade ago before it ever leaked.
So far I have:
Removed all vram and dram memory simms. No change.
Installed a new PRAM battery. No change.
Disconnected both SCSI hard drive and Floppy drive. No change.
Tested the PSU outside the machine and the 5v/12v and -12v rails all look good. So PSU doesn't seem to be suspect.
To bypass the PSU, I built an ATX adapter cable and attempted to boot the machine from an ATX psu. Exact same thing as before. So I think I can rule out the PSU as being suspect.
I started probing around the board and found a whole bunch of the tantalum capacitors that appear to be shorted to ground. The ones in the middle section of the board front to back. Not the ones under the PSU and not the ones behind the expansion slots, but the ones in the middle of the board. Both sides of these caps appear to be grounded, so something, somewhere is shorting out and causing this. I doubt all these tantalum caps are bad, so my guess is some component in that region is causing it and that's what is preventing the machine from booting.
Anyone with ideas?
I recently received a new to me Quadra 700. It was sold as not booting.
While it does power on (power led is on), there is no chime (I do hear a click/pop from the speaker) and no video. While the scsi drive spins up, it doesn't boot from it as far as I can tell.
Motherboard is squeaky clean with barely even a trace of dust. For a 30 year old machine, it doesn't look old at all. It almost looks like new old stock. Zero battery leakage as the previous owner pulled the battery out a decade ago before it ever leaked.
So far I have:
Removed all vram and dram memory simms. No change.
Installed a new PRAM battery. No change.
Disconnected both SCSI hard drive and Floppy drive. No change.
Tested the PSU outside the machine and the 5v/12v and -12v rails all look good. So PSU doesn't seem to be suspect.
To bypass the PSU, I built an ATX adapter cable and attempted to boot the machine from an ATX psu. Exact same thing as before. So I think I can rule out the PSU as being suspect.
I started probing around the board and found a whole bunch of the tantalum capacitors that appear to be shorted to ground. The ones in the middle section of the board front to back. Not the ones under the PSU and not the ones behind the expansion slots, but the ones in the middle of the board. Both sides of these caps appear to be grounded, so something, somewhere is shorting out and causing this. I doubt all these tantalum caps are bad, so my guess is some component in that region is causing it and that's what is preventing the machine from booting.
Anyone with ideas?