[Hammarlund] Re: [Boatanchors] SP-200 Help Needed

[Glen Zook]

I have run into similar problems when working on
broadcast / shortwave sets manufactured during the
1930s.  It seems that some stages need an additional
resistor added across the capacitor somewhere between
100K and 1 megohm.  For some reason the leakage of the
original capacitor was necessary for the circuit to
function.  I haven't done any "real" investigation of
just why this happens.  Since I know the "fix" I just
add a resistor and get the circuit working again.

Glen, K9STH


--- Carole White-Connor <carolew at bellatlantic.net>
wrote:

Guys, I'm working on an SP-200 (BC-794). It was
performing well with good sensitivity.
 
Tonight, I changed out a leaky .01 bypass cap on the
1st RF (6K7). After I did so, the sensitivity went
south. I checked the voltages on the 1st RF and all
are normal.
 
However, I did notice something odd. When I touched
the probe to the plate of the 1st RF, the signal
improved. I touched the antenna (through a cap, of
course) to the plate of the 1st RF and sensitivity
returned to normal. I touched the antenna to the grid
cap of the 1st RF and sensitivity was poor. The 6K7
tests good.









Glen, K9STH

Website:  http://k9sth.com

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