VT180 Robin Floppy Disk Cable Pinout

[l***@alumni.princeton.edu]

Folks,

After many hours, I have repaired the VT100 basic video card
in a VT180 Robin that I bought a few months back at a surplus outlet
(bad 8080 and problematic DC011A). So, I now have a working Robin,
sans RX180 or cable.

There's not much on the internet on the Robin. I have yet to
find the print set for the Robin board. I believe the RX180 used
drives like the Tandon TM100s found in old PCs. I have drives like
this and would like to build my own RX180.

Does anyone have the pinout for the DB37 disk drive connector
on the back of the Robin? Better yet, the print set? Any help is
appreciated.

Lou Ernst

[glen herrmannsfeldt]

***@alumni.princeton.edu wrote:
(snip)

Post by l***@alumni.princeton.edu
There's not much on the internet on the Robin. I have yet to
find the print set for the Robin board. I believe the RX180 used
drives like the Tandon TM100s found in old PCs. I have drives like
this and would like to build my own RX180.
Does anyone have the pinout for the DB37 disk drive connector
on the back of the Robin? Better yet, the print set? Any help is
appreciated.

Not specifically, but it is common to use the low pins as 1 to 34
for the normal floppy cable. (No twist, that was an IBM invention.)

Some put power on the high pins, others use external power for
the drive. It shouldn't be too hard to see which pins are
connected up. They are usually open collector drivers, so it
doesn't hurt it if it is connected wrong, unless there are power
pins. Note that the pin numbering is different for a DB37 than
for the usual 34 pin header.

-- glen

[l***@alumni.princeton.edu]

Glen,

I understand what you have suggested, but after looking at the
traces on the Robin board for a moment, I'm not seeing what I would
have expected. I would have expected one of the rows of pins (or most
of one row anyway) on the DB37 to be grounded, because the even (or is
it odd?) fingers on the cardedge connector of an SA400 style drive are
all grounded.

You have, however, made me think about tracing the pins back
on the board. I may be able to figure out which signal is on which pin
that way.

Thanks for writing back.

Lou

[l***@alumni.princeton.edu]

For the record,

The pins on a DB37 connector are numbered sequentially across
the long rows and are numbered in a zig-zag orientation for cardedge
connectors. In spite of this, the Robin DB37 floppy connector pin
numbers (and their functions) correspond to the finger numbers on the
cardedge connector on the SA400 style flopy drive. For example, pin
20 on the Robin is "step" while finger 20 on a floppy drive is also
"step". Because of what I mentioned in the first sentence, one cannot
simply use IDC connectors and a ribbon cable. Oh well.

Lou

[Eric Smith]

Post by l***@alumni.princeton.edu
For the record,
The pins on a DB37 connector are numbered sequentially across
the long rows and are numbered in a zig-zag orientation for cardedge
connectors.

For the record, DB37 coonectors don't exist. You're talking about a
DC-37 connector. See MIL-C-24308 or DIN 41652.

[l***@alumni.princeton.edu]

Eric,

Post by Eric Smith
For the record, DB37 coonectors don't exist. You're talking about a
DC-37 connector. See MIL-C-24308 or DIN 41652.

You are correct (I bothered to look into it.) I guess I learned
something today.

Lou

[Eric Smith]

Post by l***@alumni.princeton.edu
You are correct (I bothered to look into it.) I guess I learned
something today.

Well, I was being rather nitpicky. Anyhow, it sounds like you working
out the necessary wiring. I don't have a Robin, but maybe someday I'll
find one and the info will be handy.

Eric

[glen herrmannsfeldt]

Post by l***@alumni.princeton.edu
The pins on a DB37 connector are numbered sequentially across
the long rows and are numbered in a zig-zag orientation for cardedge
connectors. In spite of this, the Robin DB37 floppy connector pin
numbers (and their functions) correspond to the finger numbers on the
cardedge connector on the SA400 style flopy drive. For example, pin
20 on the Robin is "step" while finger 20 on a floppy drive is also
"step". Because of what I mentioned in the first sentence, one cannot
simply use IDC connectors and a ribbon cable. Oh well.

That is pretty bad as far as impedance discontinuity.
It is pretty important to have the ground wires interleaved.
The signal will survive over short distances, but why?

No EE would do it that way.

-- glen

[Eric Smith]

Post by glen herrmannsfeldt
No EE would do it that way.

I think you meant "No good EE would do it that way." There is no shortage
of bad EEs in the world. Or most any other profession, for that matter.