[JMS] 90800/p.s. progress

[JAMES HANLON]

Cal,

Sounds very good!  If you want the ability to run greater input to the =
90800 at this power supply voltage, check the screen voltage on the 807. =
 The ARRL Handbook rates the 807 screen for 250 volts in normal class-C =
service with a maximum of 300 volts.  If your screen voltage is a bit =
low, as it is likely to be because of your 450 volt power supply, you =
could put in a shunt pot around the existing 3500 ohm screen resistor in =
the voltage divider from the B+ line.  That would allow you to adjust =
the screen voltage and also the output from the 807 - essentially it =
would be an electronic, variable drive control for your final amplifier. =
 You might even want to put a fixed resistor in series with the shunt =
pot to prevent you from inadvertently setting the 807 screen above 300 =
volts. =20

One extra hint, if you want to measure the control grid drive to the =
807, just put a milliamp meter in series with the bias battery.  3.5 ma =
is about right for the 807 grid drive current.  If that's too high or =
too low you can always adjust the variable coupling capacitor from the =
6L6 plate to the 807 grid. =20

73,

Jim, W8KGI


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