[Milsurplus] BC-342 info needed

[W7QHO@aol.com]

In a message dated 9/12/03 5:40:29 PM, antqradio@juno.com writes:


> My question is about the mechanics of the tuning capacitor gear train.=A0=20=
I
> didn't find anything in the TO about it so I am looking for some
> guidance.=A0 The fast frequency knob has so much slop in it, it won't move
> the gear train.=A0 The veneer works well so it isn't anything internal.=
=A0 I
> pried the cover off of the knob in question and it seems that the
> mechanism relies on a friction fit to operate.=A0 So I picked up some thin
> felt washers at Lowes but the repair will have to wait till later this
> weekend.=A0 Am I on the right track?
>=20

Both the Fast Tune and Vernier knobs on the BC-342 drive the same large=20
spring loaded gear behind the front panel.   Different size pinion gears pro=
vide=20
the difference in tuning rates.   The Fast Tune shaft passes through the fro=
nt=20
panel via an eccentrically drilled brass bushing held in position by a locki=
ng=20
ring on the front panel under the Fast Tune knob.   Loosening the screws on=20
the locking ring allows the bushing to be rotated which, in turn allows the=20=
mesh=20
of the Fast Tune pinion gear to be controlled.   The proper adjustment here=20
is to back off the mesh of the Fast Tune pinion to a point where a very slig=
ht=20
amount of play can be felt on the Fast Tune control.   This allows the sprin=
g=20
loading on the large gear to fully engage the Vernier pinion and no play=20
(backlash) should be present on the Vernier control.

Several things could give the situation you describe (".....it won't move th=
e=20
gear train.").   The slip clutch on the Fast Tune knob could be so loose or=20
worn that it is incapable of passing sufficient torque to operate the rest o=
f=20
the gear train. The brass bushing could also be very badly worn. Seems more=20
likely, though, that the locking ring (see above) has come loose and the Fas=
t=20
Tune pinion has backed completely out of mesh.   This can easily be determin=
ed by=20
visual inspection.=20

For much more on the BC-312/342 receivers see Electric Radio #95, March 1997=
.

Good luck.=20


Dennis D.   W7QHO
Glendale, CA



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