[Johnson] Pacemaker Problems

[Rodger]

David,

Are you sure you have adequate drive to the mixers at 500 Khz?  How does 
the level compare  to the drive at 4 Mhz.?

Any possibility of a bad switch contact selecting one of the capacitors? 

Rodger WQ9E

David C. Hallam wrote:
> The signal goes into the grid of the 12AT7 balanced modulators but does not
> come out at the plate.  My question is why?  The way the circuit is
> designed, the 80M and 40M plate circuits of the balanced modulators use the
> same coil and capacitor to resonate them with the single change that a 1000
> pF mica capacitor is switched in on 80M.  The 40M circuit operates at 4 MHz
> and the 80M operates at 500 KHz.  The 40M output is OK but the 80M is
> nonexistent.
>
> I checked the 1000 pF capacitors with my old capacitor tester.  This thing
> is so old that the calibration is no good so I can't trust any reading for
> capacity.  However, the capacitors show no short, open, or leakage and read
> about 800 pF.
>
> I am going to replace the two capacitors but was wondering if there was
> something else I was missing.
>
> David
> KC2JD/4
>
>   
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