DEC BA11K Fan repair

Jon Elson elson at
Fri Sep 25 21:18:04 CDT 2015

On 09/25/2015 03:45 PM, devin davison wrote:
> I have a BA11K power supply out of a pdp 11/34 that has frozen up fans.
> They are frozen up pretty bad. I heard from another list member here they
> are repairable, any advice on how to do so?
> --Devin
Generally, you can remove a snap ring and pull out several 
components from the hub of the fan.  Then, there is a TINY 
phosphor-bronze snap-ring on a post in the center.  When you 
remove it, be careful to shield the fan with your hand to 
catch the ring if it flies off.  Then, the fan can be 
removed from the motor stator. If ball bearings, you can 
measure and buy replacements from Boca Bearings (or other 
source).  if sleeve bearings, you may have to drip solvent 
into the bearing area first to loosen it up, then it will be 
possible to remove the fan, and clean the bearing and post. 
Then, oil liberally with 10W oil and reassemble.  Be sure to 
oil the felts as well.  For sleeve bearings, this is usually 
a stop-gap, but will work for seldom-used gear.  The Boca 
Bearings bearings usually get noisy sooner than the OEM 
bearings, but they will still last several years of running 

Different brands have slightly different construction, but 
many of them follow the above general design.


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