[Milsurplus] BC-342 Xtal filter question, Birthday radio...

[W7QHO at aol.com]

In a message dated 5/14/2004 1:07:55 PM Eastern Daylight Time, beaconeer at elite.net writes:

> 
> The re-capping of the BC-342 has begun.  I did the power supply the other
> day.  Yesterday I did the RF section (the three bathtubs under the shield
> plate).  Since this is a working unit I'm testing it after each section is
> completed to make sure everything is working at each stage.
>

Phil,

In recapping a BC-342 the caps to watch out for are the black plastic jobs that look like large micas.  The're actually molded papers, not micas.  Besides the ones more or less plainly visable under the chassis, you will also find these inside every IF can, the BFO and HF oscillator compartment and down inside each of the RF and osc. coil boxes.  To get at the latter you will have to drop the coil boxes which involves pulling the bandswitch shaft and unsoldering the connections to the RF tubes and tuning cap.  Even then you will find a couple so deeply buried that you can only break the connection with a pair of LONG-nosed pliers and solder the replacement cap in an electrically equivalent but more accessable location.  Not as bad as it sounds but still a bitchey little job.  I've had very little trouble with the caps in the metal cans in my two BC342s, BTW. 

 
> However, there is one section of the radio that doesn't seem to be working
> properly.  The Xtal phasing has absolutely no effect on the selectivity.
> When turned to the "out" position it has greater sensitivity as the manual
> says it should, but switching it in gives the same selectivity (as evidenced
> by the 5KHz heterodynes in the SWL ranges), just lower gain.  Rotating the
> control through it's range has no effect either, other than the end stop
> increasing the gain.  Does this sound like a bad Xtal?  (Oh 
> Oh!)
> 

Try dismounting and cleaning the crystal.  There's some kind of waxey gook that seeps inside sometimes.  Also, make sure the IF strip is aligned to the crystal frequency.

For a lot more on these radios see ER #95, March 1997

Good luck

Dennis D.  W7QHO
Glendale, CA