I haven't been able to find much information about this, but I did find a small email thread about it, which I share below:
I've recently come across a device that looks like it is some kind of
disk drive test exerciser made by Western Dynex.
It's a small box with toggle switches in two groups. One group has nine
switches labeled in powers of two from 1 to 256. The other group has
five switches that appear to be two-way momentary contact (up|down) that
are labeled BUSY +|BUSY -; DEC/HEAD 1|INC/HEAD 0; INITIAL/BOT
DISK|REPET/TOP DISK; RECYCLE|LOAD REGISTER; LOAD COMMAND|CLEAR
There are no indicator lamps on the device, just the switches.
It has a ribbon cable that comes out of it that terminates in a
paddle-type board that looks suspiciously like the paddle board that
would plug into the drive electronics backplane of a DEC RK05 disk
drive.
I checked BitSavers, and there's no documents for Dynex or Western
Dynex. I did a little searching, and it looks like Western Dynex made
(or OEM'd) disk drives that were similar to the Diablo 30 drives, which
were the basis of the DEC RK05.
So, here's the questions: Does anyone know of this particular tester
device, and can it be used to exercise RK05's. Anyone have any
documentation that might explain how the thing is operated?
***
> It's a small box with toggle switches in two groups. One group has nine
> switches labeled in powers of two from 1 to 256. The other group has
> five switches that appear to be two-way momentary contact (up|down) that
> are labeled BUSY +|BUSY -; DEC/HEAD 1|INC/HEAD 0; INITIAL/BOT
> DISK|REPET/TOP DISK; RECYCLE|LOAD REGISTER; LOAD COMMAND|CLEAR
'BOT DISK' / 'TOP DISK' suggests it might be an exerciser for one of
those drives with 2 platters, one fixed and the other removable. I used
one years ago that was badged (and maybe made) by Plessey, it linked to
a normal RK11-D controller and appeared as a pair of RK05s.
> There are no indicator lamps on the device, just the switches.
What's inside it? Does it look to be simple (a few SSI TTL chips) or
complicated (lots of TTL, or a microprocessor)?
>
> It has a ribbon cable that comes out of it that terminates in a
> paddle-type board that looks suspiciously like the paddle board that
> would plug into the drive electronics backplane of a DEC RK05 disk
> drive.
>
> I checked BitSavers, and there's no documents for Dynex or Western
> Dynex. I did a little searching, and it looks like Western Dynex made
> (or OEM'd) disk drives that were similar to the Diablo 30 drives, which
> were the basis of the DEC RK05.
Err no. The Riablo 30 is the RK02 (low density) or RK03 (high density).
The RK05 might look the same to software (although there are differences
in the interface, particularly the drive select lines [1]), but internally
it's quite different (the Dioblo 30 uses a permanent magnet DC motor as the
head positioner, I am not joking, the thing's got brushes and a commutator!)
[1] The Diablo 30 has 4 1-of-n select lines. The RK05 can be configured
(by a pin o nthe itnerface connector) to either do that, or to have 3
binary-coded select lines. The RK11-C controller does 1-of-4 select, and
can have up to 4 drives (RK05s or Diablo 30s) on each of 2 cables. The
RK11-D uses binary select lines and can have 8 RK05s ona single cable.
IIRC that Plessey drive I mentioned had a little PCB that plugged into
the RK11-D drive connector containing a decoder chip to turn the 3-bit
bunarly select into 1-of-n select.
My guess is that this is some kind of drive exerciser, possibly to do
repeating seek patterns (like the ones mentioned in the RK05 maintenance
manual) that you use when settign up the postiioner waveforms. But I
don't have the docs.