I'm glad
your not working on projects for me then. Having
potentially
damaging voltage on a connector that is not
needed doesn't
sound like
good practices to me.
I don't see it like that at all...
I think Tandy were wiring the harness so any normal 8" drive sould be
used. Some drives needed the 12V, some produced it internally
from the
24V line, so Tandy provided it on the cable for those drives
that need it.
It's like PC floppy drives. Every PC I've ever worked on has
4 pin floppy
drive power connecotrs : +_5V, +12V, and a couple of grounds. Most
modern-ish 3.5" drives use 5V only. Are you saying that PC
power supplies
shouldn't connect up the 12V pin
I agree that your point is valid, but
that's not the way I'd do it. If I were king it wouldn't be so, but I'm
not.
I have the service manual here for this drive. No where does it say
that pin 4 is not connected to anything. Nor do the
schematics I have show that this drive's 7812 (which is how it
is referenced in the print)
is optional. The only source for +12 on this schematic is the 7812,
derrived from the +24v line on Pin 1.
Sure. That drive produces its 12V rail internally.
Since you have the schematics, can you tell me what pin 4
_is_ shown as being connected to, please.
Now you've got me. I didn't look
at it from this point of view. There is no trace for it. Period, doesn't exist at all.
Of course we all know that published schematics are all 100% correct (this is a dig at
schematics in general, not you Tony). There isn't even a land for it on the circuit
board on the drive I'm looking at. Physically, there are 5 black wires coming from the
AMP plug to the circuit board. Pin 4 isn't poulated and there's no open land on
the board.
Tandy also uses the same connector on the same power supply wiring
harness, but with a completely different pinout (and using the same
color scheme in some instances) to provide power to the
card cage riser
IN THE SAME MACHINE. If you use this connector on the drive
instead of
the riser, bad things happen. If you use the drive power
connector on
the riser, bad things happen. The only way to
tell them
apart reliably
is that the drive power cable has two connectors
(to power
2 drives) and
the riser power connector has only one AMP
connector.
I rememebr one of the old Sun machines (Sun 2?) that used an Archive
Sidewinder QIC drive. It has a 4 pin power connector, jsut
like the one
on a 5.25" drive. There's only one problem. The Sidewinder
uses +5V and
+24V. And IIRC the only differnce in the tape drive pwoer
connector was
the colour of thew wire to one pin.
Yuck. Then you know the pain.
Kelly