Perhaps someone has some fresh ideas? I retrofitted a fully functional
Henry 2K4 Amplifier for dedicated 6m service. I left all control
circuits intact and focused only on a replacement tank coil and two
appropriately sized plate and antenna tune capacitors along with a newly
wound HV plate choke and parasitics resistor/coil chokes. There was
nothing special or noteworthy in undertaking this type project although
this is my first for a Henry 6m. I've completed a Henry 2K4/8877 but that
was a complete tube and power supply reconfiguration with all new
wiring.
In any event, I started the process of fine tuning the 6m tank
circuit and I was up to about 500w output level with no apparent problem.
The tank was resonating at below 50mHz so the cut and try method of
calibrating the coil size began. Somewhere in that process I started to
draw plate current with no excitation. It appears to have gotten
progressively worse and now on start up (no cables attached) it
immediately draws 300-400ma. I've changed three sets of tubes, rewired
the bias circuit, changed or tested any component that could remotely be
causing my acid indigestion with no effect. Even removing the tank
circuit from the equation by disconnecting the blocking caps has no
effect on the immediate current draw on startup. The problem is somewhere
or somehow focused in the tube/HV area. I hasten to mention that I left
the floating grids in place. Henry uses them for metering. At this
point, I confess that I'm at a complete loss. What's left for me, short
of some solution that someone might suggest, is to start from square one
and ground the grids directly, reconfigure the plate current meter with
a shunt and read the current draw off the B- line and rewire the bias
with a borrowed circuit from the Ameritron Al-82. Any assistance that
would save me all that grief would be humbly accepted. I've put in about
40 hours of this fool's mission without any satisfaction. Ron W2CQM/3
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