Macintosh Plus and HD 20 SC

[bibilit]

Is there any specific procedure to boot from a 20 SC hard drive with a Plus ?

I have been trying with several with little success, the Plus can boot from the floppy, but is unable to even see the drive.

The HD is seen by another Macintosh and appears to have a valid system on it.

The curious thing is that those drives were hooked to a Plus before.

 

[Anonymous Freak]

What other Macintosh is it showing up on?  Maybe it was formatted as HFS+ instead of HFS?

 

[bibilit]

no, checked, showing on an SE

 

[Gorgonops]

Does the Plus see other drives? Sounds suspiciously like it's the problem.

 

[bibilit]

Not tested.

 

[Gorgonops]

The short answer is that the 20SC should be as plug-and-play with the Plus as anything SCSI can be so, yeah, I kind of thinking the finger is pointing at your Plus having something wrong with the SCSI port.

 

[rsolberg]

You may want to check the jumper settings on the hard drive inside the HD 20 SC enclosure, particularly if it's not the original drive. The Mac Plus doesn't supply termination power on the SCSI bus, while the SE and later desktop Macs do. Termination power is required for both active and passive termination. If your drive has a "Term Power from Bus" jumper, it should be disabled; "Term Power from Drive" or "Term Power TO Bus" should be enabled.

 

[jsarchibald]

Yep, have used HD20SC's before without any issues, so thinking it could be the Plus.

 

[Gorgonops]

There is this, which in theory *could* apply if you formatted the disk on another machine since you last used it on the Plus. When you say the Plus doesn't see it, does that include if you run the HD setup software from a floppy?

 

[CC_333]

I think it was recently discovered (can't remember where or when) that with the addition of a diode or something in an empty spot on the Plus logic board enables term power, so the circuitry for it has actually been there all along, it was just left disabled from the factory.

c

 

[rsolberg]

I also wonder about a failing filter on the logic board.