[morzh]

mrFixr

Not only I serviced and fixed these (including he microcode ROM), I had to once fix the 29MB disk drive that came bad from the factory (Bulgarian built, IZOT was the company's name). I described it somewhere, but my boss got at it first and diagnosed it to the "bad" sector label sensor, so he...well, he pried out potted coil out of it. And then, for nothing better to do, he subbed it with a small coil from his guitar pickup (about 100 times less turns) and potted it with... rosin.
Eventually he gave up.

I took over. The initial problem was not tightened nuts on all the lug contacts (not just not tightened...loose by 3 or so turns) and conformal coating on all (ALL! EVERY SINGLE ONE!!!) boards' card edge connectors that plugged into the backplane.
Once done with this, I then built an amplifier, mounted it on the pins of that sector sensor (they were stubby and rigid enough, and the amp was an OpAmp with the RC delayed input) so I amplified that 10mV (instead of 2V) signal, and then phase-shifted it, using potentiometer and different caps until the label came in just in time. I had to delay it by one turn exactly (no good OpAmps at the time, so the amplified signal cmae late, and had to be delayed then). It worked then. For some years. Even after I left.

Oh...and the cracked traces in 4-layer UNIBUS-MAP unit's board...and in memory also (2MB...whopping 2MB). I spent 2 or 3 weeks with that monster. And I did no have to, but I loved the stuff...so I did. And then this strengthened my reputation, which was a bonus.

But that was PDP11/70. The newer one, we bought two. That was purely Soviet built, no Polish parts in the computer itself.