Tuning up SB-401 w/303

[Robert Myers]

Have an SB-401/SB-303 pair connected and operating somewhat ☺

The SB-401 is set on TRCV, with its FREQ CONTROL set ‘LOCKED’ (to SB-303, of course!), both rigs have their BAND switches set to identical bands, and a good oil-cooled 50 Ohm dummy load is working fine.  The finals were just neutralised OK a couple days ago.
 
When I switch the SB-401 MODE from CW to TUNE, and then adjust the PLATE, DRIVER, and CW LEVEL as usual to try to maximize the power output into the load.  It looks OK for a while, then I see the GRID current (as measured on the SB-401 front panel meter slowly start to sink. It might start of at 1/2 FSD (1mA) then slowly (and stopping sometimes) go down to 0.1 ma.  On the 20, 15, and 10, it is even weaker; starting at 0.25 mA then over two minutes drifting down to 0.1 ma or less.

What do you think needs to be changed in the SB-401 (the 303 seems fine).

Thanks,
-- Rob

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