Stripping an RA80

Tony Duell ard.p850ug1 at
Sat Jan 7 14:00:43 CST 2017

On Sat, Jan 7, 2017 at 6:48 PM, Pontus Pihlgren <pontus at> wrote:
> Hi
> I think you should sacrifice the RA80 for a working R80. I know there
> are several RA80 in the wild but I've never heard of a R80.

Well, actually I think you own an R80 but don't know it :-)

As I understand it, the R80 had the sort-of SMD interface. 2 cables
(60 and 26 wires). It's not SMD, there are significant differences, but

The RM80 is an R80 with a Massbus interface box in the stand. Or at
least I think it is. I've not got any technical documentation on that unit.
If you have one, can you tell me what the cabling between the drive and
Massbus interface is? And if the 'personality board' (the smaller of the
2 hinged boards under the top cover) matches that in the R80 manuals.

The RA80 has the SDI interface.

The bare R80 (no external Massbus interface) was used with the IDC
(Integrated Disk Controller) on the VAX11/730. That controller can link
to up to 4 drives, one can be an R80, the others RL02s. I have the
compact 11/730 configuration, a half-height rack containing the CPU,
an R80 and a TS05 magtape (Cipher F880).

There are basically the following modules in the drive :

HDA  : I am pretty sure the physical HDA is the same on all drives. The
servo information should be the same too. Maybe the data surfaces are
formatted differently.

PSU : There are at least 2 versions of the PSU which are very different
internally (so if you are working on one you need the RA82 printset from
bitsavers as well!). But it's not drive-specific

R/W PCB. Sits on top of the HDA and AFAIK is the same in all drives

Microprocessor PCB. An 8085 and a lot of paralell I/O. It uses the 8155
RAM I/O chips and thr 8755 ROM I/O chips. And a lot of other logic too.
The ROMs are different between the R80 and RA80, but the board is the
same apart from that. Annoyingly the ROMs in the RA80 are in sockets,
those in the R80 are not....

Servo PCB. A lot of analogue and digital circuitry to drive the positioner.
AFAIK t's the same in all drives

Personality PCB. The host interface. The RA80 and R80 ones are totally
different for obvious reasons.

Control panel. A few illuminated pushbutton switches. The R80 one is
quite simple, the only electtonics on it are the lamp drivers. The RA80
one has the later drive select swtiching (wider ready lamp with a cap
that you break pegs off to set the drive number) and also has the drive
serial number, revision level, etc set by DIP switches and DIP shunts.
It still plugs into the same connector on the microprocessor PCB and
thus the RA80 control panel is stuffed with multiplexers.

Getting back to my dilemma. I need an R80. I do not need an RA80.

I may try to run the internal diagnostics on the RA80. Check the PSU
first of course.

I almost certainly will take the gas strut brackets, etc from the RA80.
Making them is a right pain!. I would consider trying to source the
screws, etc, and make the missing cables for the R80, but only if
somebody really wants an RA80 intact. I don't want to keep the thing
in my machine room for no purpose.

Rest assured that any 'useful' bits will be saved no matter what. I
will certanly keep all PCBs, HDA, PSU, motor, etc.

> On Sat, Dec 31, 2016 at 05:26:50PM +0000, Tony Duell wrote:
>> 3) Those that are of no use in the R80, but are not too hard to store
>> Personality board
>> Control panel
>> SDI cabling
> I'm curious. I have an RM80 (which I intend to use as is). But would the
> RA80 personality board be possible to transplant into an RM80 to read or
> write its content?

It would certainly need the RA80 ROMs and contol panel. I think then you could
get a working drive, but it may well not be able to read the format of an RM80
HDA. You could probably reformat the HDA to work, but that rather defeats
the purpose of what you are doing.


> /P

More information about the cctech mailing list