[ARC5] BC-669 Project for Veteran, That "Homer Moment" "DOH!!"

[David Stinson]

You know, I've revived a few BC-669s.  It's been awhile.  This "buzzing 
relay" issue kept nagging me.  I felt I had seen it before, but just 
couldn't pull the memory out of the cob-webby, dark and yawning abyss 
between my ears.   Happens all too often these days.  All the manuals 
say it's a 115VAC relay.  Its connection in the circuit says that should 
be so.

Thank you, Bill, for the clue about the "shaded pole-" a metal ring 
physically connected to the relay pole piece which acts as a "shorted 
turn:"
       "...a copper "shading ring" wrapped around the end of the
      pole piece. The current induced in the shading ring delays
      the decay of the magnetic field long enough
      to smooth it out between cycles."

Well, the relay was dirty and the contacts were intermittant anyway, so 
decided to pull it out, clean and inspect it.  The relay did not look 
like a ham mod- it looked professionally installed, following Signal 
Corps standards.  Got it out, took a close look at the coil and... No 
shading ring.  Hmmmm... Started with a little naptha, brushing the crud 
away from the sides of the coil, and these letters emerged from their 
dirt and dust covering:  "12 VDC."  "DOH!!!!"  That's when the memory 
came back, leaping out of the darkness, laughing at me and making-fun of 
my decrepit grey-matter.  I had seen this before. Now as then, I've 
scoured the manuals trying to find why this change was made.  Nothing.  
I could have missed it...

Anyways... Maybe it was done because these were used mobile? But why do 
that?  Yes; the rig has a vibropak to run the receiver from 12VDC, but 
that won't run the transmitter, so why change the antenna/TR relay?  No 
use for it without 115VAC power to the transmitter transformers.   Now I 
don't remember what I did about this in the past.  Guess I'll have to 
open-up my station set and look, after which *another* memory will 
bush-wack and embarass me.  I'll let you know.

73 OM DE Dave AB5S




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