[Elecraft] KPA100 D13 Cathode High Voltage

[Ron D'Eau Claire]

Michael, change R4 to 100K. That change is necessary to keep from applying
excessive voltage to some components in the KPA100. Your amplifier may work
for indefinitely with the higher voltage (or not), but you are
over-stressing some parts. 

Ron AC7AC

-----Original Message-----
All,

I performed the voltage checks at the KPA100 Test Points as stated on page 
43 of the KPA100 manual (rev. C, Feb. 11, 2004).  The D13 cathode should 
have a voltage between 90 and 150 volts; the measured voltage is 175 volts, 
which seems a little high.  Also, the voltage measured at U4 pin is -30 
volts, but the manual indicates the voltage range should be between -5 and 
-25 volts.

Consulted the schematic and it appears as if the voltage from pin 8 of U4 
supplies the High Voltage Bias Supply circuit.  Mesaured the voltage at C44 
as 45 volts, but schematic indicates it should be 30 volts.

Is 175 volts too high a voltage at the D13 cathode?  R4 is 39K.

Any suggestions or help would be greatly appreciated!

Michael
KI5E