[Hallicrafters] SX-42 BFO glitch

[Craig Roberts]

Well, I'm finishing up my third SX-42 rebuild (one for me, two for ham 
buds) and I've run into a curious anomaly.  The BFO is "twitchy".  The 
note is unsually unstable and prone to shifting with mechanical 
disturbance -- kind of like an old regen receiver.

The CW Pitch control (a variable cap) mounting was bad when I acquired 
this radio. One of the two mounting screws had been broken off and a 
former owner had stuffed foam btween the mount and front panel to 
stabilize things.  I rectfied this by drilling out the broken mounting 
screw and installing a new one.  The control is now mounted tightly.  
The formerly stiff variable cap has been cleaned and lubed and now 
rotates smoothly. Yet, the warble remains.  Oh -- I also rebuilt the BFO 
transformer with new mica caps. This gave me more injection, but did not 
cure the instability. 

Any ideas?

Many thanks again,

73,

Craig
W3CRR