First VAX-11/730 VMS Boot! (was: Re: VAX-11/730 %BOOT-F-Unexpected Machine Check)

tony duell ard at
Fri Jun 12 16:07:24 CDT 2015

> I don't remember exactly what I have, but the binders that came with my system might include an R80 manual (to 
> be scanned, of course!).

Bitsavers has the service manual, pocket service guide and printset.

The service manual is, as I would expect, a module replacement level manual. It is useful because it 
documents the drive diagnostics, how to use the 2 hex switches and the LEDs on the microprocessor
board. Trying to debug an R80 without that is going to be a lot of work!

The pocket service guide is a quick-ref to the diagnostics and has a rather better internal cable
diagram than the service manual

The printset is of course the full schematics. Alas no PROM dumps (not just the microprocessor board [1]) 
but also the servo board has a couple of PROMs and the personality board has as state machine
built round 82114s (PROMs with built-in latches). Something to investigate sometime. 

[1] The control processor is an 8085, the firmware is mostly in 8355/8755 ROM+I/O chips. I think there
is a conventional 2K ROM there too, There seems to be a total of 10K of firmware which seems like
quite a lot.

I doubt DEC ever published the firmware source, but it can't hurt to ask here :-)

Oh yes, the PSU. The R80 printset shows the original version. Mine has a later PSU. The RA81 printset
contains most of the schematics, for some odd reason the motor control relay PCB [2] is missed out, my
guess is it was a simple error. The RA82 printset contains the complete PSU schematics.

[2] The spindle motor in all these drives is a capacitor start induction motor. The capactor is in the top
chassis with the logic PCBs. Unlike most such motors, the starting winding is not controlled by a speed
operated centrifugal switch. Rather, there are 2 relays in the PSU, one for the run winding, one for the
starting winding. They are controlled by the microprocessor, which checks the spindle speed via the 
optoswitch on the bottom of the HDA

The RM80 is an R80 with an external massbus interface. AFAIK all RM80 drive spares, docs, etc apply
to the R80. The RA80 is also very similar (different personality (interface) PCB, different firmware, but
otherwise much the same). The RA81 and RA82 are electroncially quite different, but mechanically
similar and it's worth reading their manuals with that in mind. The RA82 printset (I think) has some
information on how the HDA was assembled. It appears that the spindle/disks are assembled
into the lower metal case, the upper case is fitted and bolted down, then the positioner/heads slides in
from the front (I assume with some tool to keep the heads apart). Then the head and positioner
cables plug into a PCB on HDA front cover which fits in place and is clipped down. Of course
all this has to be done in a clean room. But for some odd reason the schematics of that 
HDA head PCB are in the printset, for all they are pretty much useless for repair (custom ICs 
that you can't get to without dismantling the HDA in a clean room).


More information about the cctalk mailing list