Classic won't boot with SCSI CD-Drive connected

[68K-Trooper]

Hello,

My Mac Classic (OS 7.0.1) doesn't boot anymore when the SCSI CD-Rom drive is connected. I get the question mark. As soon as I remove the scsi connector it boots up. The drive used to work fine and I didn't make any changes to the drivers or any other software whatsoever... The SCSI ID is set to 3 on the CD drive...

Does anyone know why it's doing this?

Any help appreciated.

George

 

[Classic Mac]

sounds like scsi id or termination problem; try changing id to 6.

 

[68K-Trooper]

Thanks for your reply ClassicMac. I already tried all SCSI IDs on the drive. I also have a termination plug plugged into the 2nd scsi connector on the CD drive.

Am I missing something?

 

[envirogeek]

Have you tried zapping the PRAM?

Could be a classic case of SCSI voodoo.

Try all permutations of cable connections on/off that you have available to you whether they seem to make sense or not, with the drive ID set to the original 3.

Cable to 50 pin drive connection 1, terminator on 2.

Cable to 50 pin drive connection 2, terminator on 1.

Cable to 50 pin drive connection 1, no external terminator.

Cable to 50 pin drive connection 2, no external terminator.

Is your terminator an end plug or a pass through? If pass through, try putting it on the cable first before connecting it to the drive, then on connection 1 and 2 in order.

If you have tried a different 25-50 pin cable, and tried with external terminator on and off I would confirm that your drive and cables work on another machine.

Do you have any other machines with SCSI around you could connect the CD drive to for confirmation that the ID change is really happening?

Perhaps the push wheel is pooched or no longer actually connected internally on the CD drive board?

If you have documentation for the CD drive I would pull off the drive case and check internal jumpers for termination and/or termination power, then try connecting it again without any internal ID jumpers which would probably give it a SCSI ID of 0 or 1.

Hope this helps.

 

[Charlieman]

envirogeek has some good suggestions.

Can you boot from floppy and run SCSI Probe with the existing devices attached?

How long is your SCSI cable? Shorter is better.

My instinct is to suspect that SCSI termination power is absent, simply because it is a 68000 compact. Do you have an external hard drive that you can place in the chain which might deliver Term Power? You could even try using a SCSI Zip or Syquest drive.