DEC R80 HDA details

Jon Elson elson at
Fri May 31 10:09:46 CDT 2019

On 05/30/2019 02:20 PM, shadoooo via cctalk wrote:
> Hello,
> I'm in the process of cleaning and hopefully restore to operation of a DEC
> R80.
> The unit has some minor sign of corrosion, however it's VERY dirty, even
> inside the hood.
> The filters are obviously to be removed and replaced, as they are
> disintegrating.
> Also foam parts between the boards must be replaced.
> Aside from obvious parts, there's something that should be replaced /
> cleaned inside the HDA (foams, filters or rubbers), which could damage the
> disk permanently in case it's turned on after decades if not "cured" before?
> Anybody has some good pictures of the HDA inside, after cover removal?
I don't think this is a field procedure.  Definitely, way 
back around 1980 or so, they had some bum adhesive that held 
the internal filter in the RA80 and RA82 HDAs, as I recall, 
and they had to replace all HDAs in the field, over time.  
They had some scheme where the oldest HDAs were replaced 
first, as the adhesive degraded over time, so they knew they 
had a couple years since new before the problem would 
occur.  It was a BIG expense for DEC.

Presumably, all of these HDAs (that were under maintenance 
contract) that had the bad adhesive in them were replaced 
years ago.  As far as I remember, there IS no removable 
cover on those HDAs, they were hermetically sealed except 
for a tiny, filtered, pressure relief vent.
I think the procedure to update those HDAs was a pretty 
involved disassembly.


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