[Milsurplus] "Correct" fuses for BC-342??

[Philip Atchley]

Dennis,
Some interesting comments.  Yes, I thought the fuse size was rather odd
either for the filaments or the dial lamps.   In the BC-342 there is another
odd thing about the filament fusing.

The center tap of the transformer is grounded.  In one side of the
transformer there is a 10 Amp Fuse, in the other side, nada!  If there were
to be a short in the unfused side the power transformer would probably do a
meltdown, UNLESS the primary fuse blew first.  I was lucky, the tube pin
that had a short to ground (pin 7 of the first mixer) was in the fused line
and blew, letting me know I had a problem.  I suppose if one were really
concerned about it he could wire the "spare" fuseholder to the other side of
the filament transformer.

73 from the "Beaconeers Lair".
Phil, KO6BB

> > The correct fuses are 10 amp 25 or 32 volt.  Hot filament current is
about
> > 1.3 amps.  At turn-on, probably twice that.  I'd check C78 and C79 and
the
> > filament wiring.  Remember that if the RA-20 is connected to the radio,
C79 will
> > show low resistance to ground through the filament winding (center tap
is
> > grounded).
> >
> > The BC-312 and BC-342 both use the same front panel fuses.  In the
BC-312,
> > the DM-21 also runs off of the filament fuse, which is why
> > it is labeled
> > DYN-FIL.
>
> Robert is correct but there are a couple of interesting side issues here.
Makes sense to use a 10 amp DYN-FIL fuse on the BC-312s but always seemed
strange to me that a fuse with the same rating was retained in the 342.  The
LAMPS fuse is also rated at 10 amps but the circuit only drives a pair of
pilot lights. In early sets (312 and 342) this fuse also provided current to
the oscillator compartment heaters which might explain the original rating.
On the 312s this circuit is also wired out to the 3-way SPEAKER SECOND AUDIO
jack to run early speaker field coils. Both features (heaters and field
coils) were dropped early on but the fuse rating was not changed.
>
> Dennis D.  W7QHO
> Glendale, CA
>