Stripping an RA80

allison ajp166 at
Sun Jan 8 14:57:42 CST 2017

On 01/08/2017 01:46 PM, Robert Armstrong wrote:
>> Tony Duell <ard.p850ug1 at> wrote:
>> R80 the lines are outputs from the drive giving the coding of the ready lamp cap
>   I was always thought that the R80 had to be unit #0 to function, but I admit that I've never tried anything else.  I wonder if that's not true??  The RL02 drive(s) on the IDC can be any of units 1, 2 or 3.  
>> The HDA is the only major unit I can't repair (yet!).
>   Yeah, same here.  In addition to the 11/730 with one (dead) R80, one RA81 and one RA82, I have a MicroVAX-III with an RA82 drive.  Keeping them all working has been a real challenge.  Fixing the electronics and mechanical parts isn't too bad, and I have plenty of spares, but the HDAs don’t seem to be very reliable.  I get the impression that they were designed with a finite number of spin up/spin down cycles in mind, and once you exceed that limit they die.  Fortunately I've been able to find spares for the RA81 and RA82 HDAs, but R?80s seem to be pretty rare.
> Bob
Depending on vintage of those HDAs they may have been in the large pool
of SNs that had bad (incorrect) adhesive
used to assemble the platters and would after about 1.5-2.2 years of
spinning would have the glue migrate out
and take the heads.  It was a major program to recover those that had
not yet failed and replace them and make
nice to those that had failures.   The adhesive used was substituted in
manufacturing without ECO.  The internal
program was costed at something north of 100M$ to achieve.

All my VAXen and PDP-11s use RX, RL, RD, and RZ media due to
reliability.  The only ones worse was RA60 then RC25.



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