Hello,
Hello,

I have a BC-342 receiver that has (mostly) been converted using an old
Surplus Conversion Manual. I am a little worried about this method
after tracing out the wiring (workmanship is pretty bad) and making
some voltage measurements.

The conversion raised the screen voltage on both 6K7 RF amplifiers by
lowering the high side of the screen grid voltage divider from 40K to
20K ohms and lowering the cathode resistors. This results in screen
to cathode voltages of about 160 VDC. The tube manual lists maximum
screen voltage at 125 VDC.

Using 33K in place of the recommended 20K lowers the screen to a
little over 130 VDC.

Am I crazy or isn't the original screen configuration better than the
conversion? Also, any opinions on trying to regulate the screen
voltage (to ground) with a 125 volt zener diode? I know zeners are
sometimes used in special circuits to produce broadband noise and
don't want to introduce noise on the sensitive screen grids of the RF
amplifiers.

Finally, the conversion removes the first RF amplifier from the manual
gain control. Is there a better method (cheap way to delay gain
reduction). Perhaps diode with the anode at the high end of the gain
control and the cathode to the cathode of the first RF amp?

Any thoughts?

Thanks.

John, W0GN