[Milsurplus] BC-611 Repair Tip

[Mike Feher]

Wow, Dave - That looks more like if it was melted rather than shrunk over the years. 73 - Mike 

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell NJ 07731
848-245-9115

-----Original Message-----
From: milsurplus-bounces at mailman.qth.net <milsurplus-bounces at mailman.qth.net> On Behalf Of David Stinson
Sent: Thursday, October 1, 2020 10:36 AM
To: milsurplus at mailman <milsurplus at mailman.qth.net>
Subject: [Milsurplus] BC-611 Repair Tip

While working on the previously mentioned BC-611s, I was lubricating the shafts of the air variable caps when one of them seemed to bind.  I removed it and found the insulating covering over it had shrunk with age and was binding/bending plates.  I pulled the cap:

https://photos.app.goo.gl/8bUR6ZAWif4yPxu17

It turns-out finding this was a "blessing in disguise."
Removed the plastic and found heavy corrosion on every mechanical and soldered part of the cap.
The red arrows point to locations which showed open connections to their respective parts.
None of the parts showed any continuity between them and their respective connection points, not even the "soldered" rotor leaf spring.

https://photos.app.goo.gl/C8Y8RA8Qx1myX7Hf9

Repaired the plates, then carefully scraped the lead-oxide bubbles off the the rotor leaf spring (away from your face, since you don't want to ingest that stuff).
Re-soldered the two stator posts and
the leaf spring contact.
This left a bunch of black residue and little balls of solder, which I cleaned away with Naptha, since we don't want those lead bits getting in the plates.  Once the naptha evaporated, used De-Ox-It on the rotor leaf spring and oil on the shaft.  It took two doses of Deoxit and dozens of turns on the rotor shaft to make the contact reliable.  Hasn't failed since.

Before re-installing, the stator posts solder point on the front face of the cap must be insulated.  A cut piece of black tape will do.

I think I'm going to pull the caps from the other rigs.  Better to fix them now than have to do it later.

GL OM ES 73 DE Dave AB5S


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