[Milsurplus] BC-221 types

[J. Forster]

When you say 'gone bad' what do you mean? Open? Leaky? Short?

If you look at the print, only LC components are bandswitched.

-John

=============



> I have seen the issue that John mentions also. My theory (I can't test
> this since I don't have that particular unit any more) is that the cathode
> bypass capacitor of the 6K8 - a .001uF Micamold I think - has gone
> bad. Since the two cathodes of the triode-hexode are common, this
> could affect the RF characteristics of the triode grid circuit.
>
> 73, ian K3IMW
>
>
>
> On Mon, Jul 29, 2013 at 10:08 AM, J. Forster <jfor at quikus.com> wrote:
>
>> I also have an -AK in a wooden case, but it has a very odd issue.
>>
>> On the high band, the unit is spot on.
>> On the lower band, the COMPENSATOR does not have enough range to allow
>> the
>> dial and book settings to be matched.
>>
>> As nearly as I can figure, the horizontal, tubular ceramic inductor must
>> have decreased in value, but I just don't see how that's possible.
>>
>> Any ideas?
>>
>> -John
>>
>> ====================
>>
>>
>>
>> > I have owned a number of BC-221 freq meters over the years.  If you
>> have
>> > a calibration book WHOSE SERIAL NUMBER MATCHES THE INSTRUMENT, these
>> > meters are darn near on the money!  I have seen units before at
>> hamfests
>> > which had a cal book that been taken from another instrument.  Watch
>> out
>> > for that!  The great thing is that the frequency-determining
>> components
>> > of these meters are 100% mechanical -- a wax-coated coil and a
>> variable
>> > cap milled out of a piece of brass.  Unless there has been physical
>> > damage to the meter, it should be within a few Hz of WWV.  I have put
>> a
>> > number of the crystals in these units  up against WWV and could barely
>> > detect a low-frequency beat note.  The only unit I currently have is
>> an
>> > AK model in a lightweight TS-164 aircraft housing.  There's enough
>> room
>> > in the back of the TS-164 to build a solid state power supply which
>> puts
>> > out 135V at about 20 mA and 6.3V at about an amp.  Watch out for paper
>> > caps in these old units - they are notoriously failure-prone -
>> including
>> > the 'molded paper caps' that masquerade as micas.  The oil-filled
>> > bathtub caps are probably OK unless they're leaking.  Oh, BTW, you
>> > really need to use a (relatively) high-Z headset like an HS-30 with
>> > these meters.  You won't hear anything if you plug in a modern 8 ohm
>> > headset.  Hallicrafters made a tube-type AC supply called the RA-133
>> > that fits in the back of one of the big metal-cased BC-221s
>> >
>> > Here's the definitive reference for the entire series of BC-221 freq
>> > meters:
>> >
>> >     http://w5jgv.com/downloads/BC-221_SCR-211.pdf
>> >
>> > The half-tone photos aren't too readable, but the book is invaluable
>> for
>> > anyone interested in BC-221s.  I've also seen the book (TM-11-300)
>> turn
>> > up from time to time on E-Pay.
>> >
>> > I love these old meters.  Over the years, I've rebuilt and refurbished
>> > more than I can remember, including replacing some really badly-hacked
>> > homebrew AC power supplies.  I'm sort of a sucker when I see one
>> sitting
>> > neglected under a table at a hamfest. They may be 70 years old, but
>> > they're still nice to have.  You can't put a receiver on frequency
>> with
>> > a counter!
>> >
>> > If you'd like to have a copy of the pdf for the RA-133 power supply
>> and
>> > the TS-164 aircraft housing, please email me direct.
>> >
>> > Hope this all helps ...
>> > Mike, WB0LDJ
>> > mharmon at att dot net
>> >
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