[Heathkit] Apache Negative Clipping Circuit

[Robert & Linda McGraw K4TAX]

Some years ago on the AM Reflector there was a circuit published, primarily 
for BC transmitter applications, that used several diodes and a "keep alive" 
power supply to provide negative clipping.  Reports are that it worked very 
well and was quite clean.  I wonder if anyone has applied this approach to 
the Apache?  I've done the other audio mods and the reported audio is 
"great" and it looks and measures quite good.  Of concern is the fact that 
the negative clipping circuit application does increase the average power or 
duty cycle with regard to the modulation transformer.

One other thing that I have observed with my transmitter is that the series 
0B2 regulators for the PA screen voltage fires on modulation peaks thus 
limiting the voltage on the 6146 screens and thus the positive modulation 
suffers.  I've checked the circuit and wiring thinking that there is a 
wiring error but have yet to conclude that one actually exists.  At the same 
time in review of the schematic, it would appear that the series 0B2's are 
not in the circuit on AM but used only for SSB.

You comments and feedback appreciated on these two issues.

73
Bob, K4TAX