Terak 8512 external 8 inch floppy drives

John Foust jfoust at threedee.com
Fri Mar 13 12:07:51 CDT 2015

I'm tinkering to connect the CBMStuff.com SuperCard Pro to 
eight-inch floppy drives.  The SuperCard has a contemporary 34-pin
floppy connector.

The Terak 8510 main unit held a drive and its system cards, and its
external 8512 drives just held a power supply and a floppy drive.  
The ribbon cables between 8510 and 8512 are 40 pin.  The 8512 doesn't 
have its own power switch.  

The back of the 8512 has a small circuit board.  (And by "back", I mean 
the board is actually exposed, which seems odd for a computer that's
otherwise built as robust as aircraft or mil-spec.)  It accepts the 50-pin 
cable from the internal floppy drive and has two 40-pin male for 
daisy-chain ribbons to the 8510 and additional 8512.  The board has a
socket for a drive terminator and a DIP for setting the drive ID.

The 8512 power supply has a relay that must be sensing a signal on
the 40-pin cable, as that's what turns on the 8512.  Similarly,
the Terak main unit's single power switch controls the Terak mono monitor.

I haven't traced the signals on the board yet, and I have not yet found 
a doc that explains the cable pin-out.  Because I have a bunch of 8512,
it would be convenient for me to be able to use them as self-standing
eight-inch drives.  

I purchased one of John Wilson's 50-pin Shugart to 34-pin adapters
for its generation of the TG43 signal and the LED blinkenlightz.

I'm tempted to tease out the Terak's 40-pin pinout and perhaps make 
some sort of adapter to go to 50-pin.

- John

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