Hi, I just recently bought a Henry 2006A VHF amplifier. It uses a single
3cx800a7 tube. I was not sure how long it was since the amp was powered
up so I brought it up on a 120 volt variac although the amp is wired for
220 volts. When I applied power at about 40 volts the plate current
meter showed 100 ma of current and grid meter read in a negative
direction. I immediately shut off the amp and made sure the HV was not
present and removed the tube. I powered the amp back up and everything
looked normal, no plate or grid current indications. I increased voltage
over a couple of hours at about 20-30 volts at a time and the HV meter
finally read 1200 volts with 120 volts input. I placed the tube back in
the amp powered it up again and the meter showed 100 ma of plate
current. The next thing that happened was that R9 (wire wound resistor)
just before the high voltage enters the pa cage opened up with plenty of
sparks. I can remove the tube and the HV still looks good on the meter
in the HV position. I really checked this amp over good before applying
any power and it looked good and clean with no signs of arcing or
previous damage. I do have a grid meter connection on the back of this
amp terminated in a RCA jack. I can not find this on any schematic that
I have been able to download. This amp also uses 8 filter capacitors but
the schematics I have show only 6. The parts list show R9 as a 4 meg 7.5
watt wire wound resistor, is this the correct value? I am thinking I
have a bad 3cx800a7 but I have no way to test it. I am having difficulty
finding good information on this amp. Any advice would be greatly
appreciated. I really want to get this amp going on 6 meter SSB. Larry,
AA4VI
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