[Milsurplus] Setting the BC-342 dial, I found a way (undocumented in manual)

[Philip Atchley]

Hi All,
Well, after "giving up" on trying to repair the National NC-300 and taking
it back to the owner I put the Farnsworth BC-342N back on the bench to
continue it's general overhaul.

One of the problems this set had was that the tuning dial wouldn't go all
the way to "zero" with the capacitor fully meshed, and all bands seemed to
be off by "approximately" the same amount physically, indicating the problem
was more likely to be mechanical than electrical alignment.

A query to both the Boatanchor and Mil-surplus mail lists netted no answers.

I "DID NOT" want to disassemble the entire gear mechanism if I could help it
but decided to get brave today and pull the front panel and see if I could
remove "just" the dial gear and re-install it properly.  First I fully
meshed the tuning capacitor plates to prevent damage.  Then I pulled a
number of knobs off to get ready to pull the panel, removed the dial lock so
I could remove the vernier tuning knob.  Then I gave the vernier knob a
twist anticlockwise to loosen the setscrew in the vernier bezel.  Now, if
the gear train were solidly "locked" that knob shouldn't have budged.  It
DID BUDGE!  At first I thought it was just slippage on the shaft as perhaps
the setscrew was loose.  Nope!  The Main Dial that had read a little above
zero now read zero.  I gave the vernier a little more "twist" and the main
dial went below zero! (tuning capacitor naturally didn't move).

So, I reassembled the whole mess (after cleaning behind the knobs).  Turned
the radio on and checked it against WWV at 10MHz.  Where before the dial had
read 10.180MC, it now read 9.9MC!  So, I had overshot.  Went back down to
the bottom of the dial and tried to go the other way.  Nope.  Had to go to
the top of the dial to move it up (makes sense, huh).  After going back and
forth a couple times I got band it to read exactly 10MC on WWV.  I then went
up two bands and checked 15MC.  Almost but not quite dead on, it reads 15KC
high!  In checking WWV 5MC on another band it is within 10KC.  NOT TOO
SHABBY FOR A 50 YEAR OLD RADIO THAT HASN'T BEEN USED OR ALIGNED IN WHO KNOWS
HOW MANY YEARS!

Anyway, apparently, from everything I can determine, this is not a
documented dial "calibration", at least I couldn't find it in the manual.
Again, to set the dial, do this.  At least it works on my BC-342-N, I
presume it'll also work on other series of this radio (BC-312 etc).

1.  To make the dial read lower in frequency, turn to the lower limit of the
frequency range, to the stop,  with the main tuning.  Then, use the vernier
to tune the set still lower!  If you go to far, use procedure #2.
2.  To make the dial read higher in frequency, tune the radio to the upper
limit of the frequency range, to the stop, with the main tuning.  Then use
the vernier tuning to tune still higher.


73 from the "Beaconeers Lair".
Phil, KO6BB

DX begins at the noise floor!
Merced, Central California
37.18N  120.29W  CM97sh