SCSI anomalies on all my older Macintosh's

[Outlander]

Been awhile but I've been having strange anomalies on almost all of my older macs. From my Plus's to my 9600. For instance, my Macintosh Plus's will no longer boot from an external HD. It doesn't matter what HD, or what enclosure I use, they just sit there at a grey screen. My 9600 will no longer boot or work with an external SCSI anything plugged in and as soon as a device gets plugged in the machine will just freeze until it's unplugged. Now to my latest issue. My Performa 475 will boot and I can install any Mac OS I want on the internal HD, but as soon as i unhook the external drive, the machine will no longer see the internal HD. I've tried 4 HD's

Is anyone else having these strange problems on other machines? Could this be a bad cap issue? 

Share your experiences, any help is appreciated! Thanks

 

[sstaylor]

Anyone in your household plug your external SCSI devices into a PC parallel port?

 

[Outlander]

Anyone in your household plug your external SCSI devices into a PC parallel port?

Lol. No, but interesting reply. And some machines have internal scsi issues while others have external. I just tried re-capping my 475 and screwed up two pads. Trying to fix these now and see if I get proper operation afterwards. On the 475 I'm thinking it's something with termination on the logicboard on the scsi bus because if I plug a terminator into the back, the machine starts booting off the internal HD

 

[Trash80toHP_Mini]

How many different Cables have you tried with the externals? If there are resistor packs involved, remove/re-seat them on drives and in cases. Internal termination will be on the drive, not on the 475 mobo.

 

[Outlander]

A little update. Finished re-capping the 475 logic board and the same anomaly still occurs, no internal HD will work without an external termination. I also finished re-capping my 6100 PM and all of the HD's booted without issue in that machine. There's also something more funky going on as the 475 will not boot Mac OS 8.0, or 8.1, it just presents an unhappy mac face when I try to. Have a feeling this 475 board is shot. 

 

[johnklos]

Just a thought - are the computers plugged in to the same set of outlets as the external SCSI enclosures?

 

[Outlander]

Just a thought - are the computers plugged in to the same set of outlets as the external SCSI enclosures?

No. But after the re-cap, my Powermac 6100 is functioning normally again. I will re-cap my 9600 next. The 475 is still not acting right. Won't launch Drive Setup either. Says it's not supported on this Macintosh