Does Apple II actually use -12v rail from PSU?

[uniserver]

Or is it just Available in case its needed for RS-232 or something?

 

[david__schmidt]

The Disk II uses -12v...

 

[uniserver]

the older style ribbon cable kind or also the newer style thinner plastic case one as well? thank you.

 

[Blinkenlightz]

According to several sources (see: http://en.wikipedia.org/wiki/Disk_II#UniDisk_5.25.22_and_Apple_5.25_Drive and Google your way around the rest...), Disk II controllers and Apple 5.25 drive (Or UniDisk 5.25) controllers are completely compatible. Conversion cables exist in both directions without anything fancy - one connector per end, no extra power taps etc.

So - the -12v line is present on both, and the drives are interchangeable. We know that so far. Whether the drive itself uses that line internally is unknown... There could be variations there. But the interface and cabling standard maintains the -12v line into the drive cabinet.

**EDIT: According to the page at http://www.vintagemacworld.com/drives.html, section "Apple 5.25" Drive (A9M0107)":

Generally, the Unidisk 5.25" and Apple 5.25" drives are interchangable. However the Unidisk version requires -12V and cannot be used with the LC Apple IIe Workstation card.

So, it seems that the UniDisk 5.25 drive and Disk II actually use the -12v, and the "Apple 5.25 Drive" does not - the LC IIe Card doesn't provide it, and therefore is only happy with the drive marked "Apple 5.25 Drive" (Part # A9M0107). I would take that to mean that a IIe without -12v available would have the same limitations.

 

[uniserver]

Well the apple IIe card does not provide it because the LC PSU does not have a -12v rail

Hey, Thank you for all that great information

So that means in the apple IIe / IIgs all that leaves is RS-232 that might need -12v



Unless there are some some other cards that may require it for something.