[Amps] Questions, regarding a Pair of 4-400A's.

[Eric Thielking]

I have a few questions, regarding a HB pair of 4-400A's, operatng in grounded grid (3.5 KV on the plate).  Specifically:


1.  How 'hot' can a 4-400A run?  What range of colors is acceptable for proper operation of this tube?


2. The output appears low,(200-300 watts, with 40 W of drive) and there is no great 'dip' in plate current, regardless of the settings of the load and tune caps.   To tune the output, I used a watt meter. What is a good way, to determine rough settings of the load and tune controls, for proper operation?


3.  The design of this amplifier appears to be similar to an amplifier in the 1982 ARRL Handbook. Plate current, with no input, but PTT closed, is 120 mADC.   How much drive should create 1000 watts of output?  How much ofr 1.5 KW output?

Any assistance would be appreciated. 

Eric Thielking