DEC RK07 drive interface specs wanted

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Tue May 18 18:23:49 2004

>
> >>>>> "Tony" == Tony Duell <ard_at_p850ug1.demon.co.uk> writes:
>
> >> [%] I don't usually like to use phrases like "field circus" (or
> >> "salesdroid" or similar denigratory mutations), but in this case
>
> Tony> I don't know why you avoid such terms. They are sadly all too
> Tony> appropriate.
>
> Like many stereotypes, they have some basis in reality. Not
> necessarily a large basis, though.

I suspect this may depend on the era of field servoids you came across. I
came across the ones at the end of the 80's, and the few I saw were
pretty clueless.

> We had an RC64 drive that was acting up. He hadn't ever worked on one
> but he volunteered to give it a try. Spread out the schematics,
> poked around, diagnosed the problem as a bad motor bearing. Rather
> than hit us for a new motor from DEC (the system wasn't under
> contract) he took it to Appleton Electric Motor company, where they
> replaced the bearing, and it was good as new.

A somewhat counter-example. At one place I worked, the VAXen were on a
service contract, but the older peripherals, like the VT100s, VT220s and
LA36s were not. Anyway, we had an LA36 that was malfunctioning, blew its
carriage motor fuse, etc. Anyway, I decided to repair this one morning,
when coincidentally the failed servoid was around for some reason. I got
out the prints -- the failed servoid was amazed that (a) I had them and
(b) I could understnad them. Didn't take long to trace the real problem.
A sheered key on the carriage motor pulley. This meant the motor didn't
stop when the carriage hit the side frame, but carried on turning slowly.
The motor had then overheated, the insulation had burnt off the windings,
the currnet had gone even higher, and so on. Failed servoid was equally
amazed that I could figure this out.

OF course there was only one solution, to rewind the motor. Took it
apart, drew a diagram of the connections to the commutator, unwould the
old wire, wound on some new with a friend helping me. Then put it all
back together. Worked fine for a few more years. That failed servoid was
still trying to sort out whatever problem he had come for when I had that
LA36 cased up and running.

Sometime I will have to tell you of the story of ARD (aged 10) .vs. the
TV rental company servoid. My parents have been regretting this ever since...

-tony
Received on Tue May 18 2004 - 18:23:49 BST