25 Jan
2007
25 Jan
'07
6:24 a.m.
The wiring
harness is made by Tandy, in the Tandy 6000. That this
harness has power going to a drive power plug that isn't used it typical
of Tandy's shortcuts. They banked on the fact that Tandon would NEVER
put another pin in that socket.
I think that's a rather strange conclusion to some to.
I'd think of it more like this ;
Some 8" drives need the +12V supply, and when it's needed it's on pin 4
of the connecotr. So Tandy wired the harness to allow for such drives.
This particular Tandon drive doesn't need 12V, so pin 4 is missing (or a
no-connect).
How can _adding_ a wire to a harness be a shortcut?
-tony 
25 Jan
25 Jan
3:21 p.m.
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 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.
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.
-tony
3:58 p.m.
Tony Duell wrote:
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.
Whoo - I think you might have got it :) I was casually reading this thread and
had a hazy memory of seeing inside some system where there was what looked to
be a "standard" power connector when in fact it wasn't. I think you're
probably right, and the Sun2 was it... trying to remember's been nagging at me
all day :-)
26 Jan
26 Jan
3:06 p.m.
Tony Duell wrote:
I know for a fact that the Archive Sidewinder uses +5V and +24V, and uses
the same type of power connector as a normal 5.25" drive. The Sidewinder
is the tape drive that was used with the PERQ, which is how I came
across it.
I don't own a Sun 2, but I've heard about the 'odd' power connector, and
can certainly believe it.
-tony
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.
Whoo - I think you might have got it :) I was casually reading this thread and
had a hazy memory of seeing inside some system where there was what looked to
be a "standard" power connector when in fact it wasn't. I think you're
probably right, and the Sun2 was it... trying to remember's been nagging at me
all day :-)
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