Am still going over the old TS-820 and found another problem re the
meter. It is important when replacing the meter to check the condition
of the multiplying resistors on the underchassis "HT" board and adjust
to suit the actual sensitivity of the meter.
Mine was reading 730 volts off load for final anode voltage but my
trusty old Avometer tells me that it was actually 1,040 volts.
Now this is WAY above the recommended anode voltage for even a 6146B
but since the tansformer secondary is 800 volts its probably correct.
I've now got the voltage reading correctly on the meter, but I'm now
very convinced that the reason for flashover in some 6146's is simply
excessive HT voltage. The finals are running in very dangerous
territory. Just a bit of SWR then Poof!!!
I'm now considering modifying the case and using a TT21 as a final.
These can stand the voltage with ease, are very easy to neutralise
and can give a good 65% efficiency in AB1 up to 30 Mhz. Will give me
around 80 watts out I reckon.
Just that my final box will be a bit taller and the old case will need a
bit of chopping about.
But then its an old rig and it might as well work properly, even
modified. Anyone elese tried major final tube changes in the Kenwood
hybrids?
=========================
Cliff , Does the TS-820 HV transformer have just 1 HV output or is there
also a lower voltage tapping.
I recall that the early Yaesu FT400/500 series (valve)transceivers had a
transformer with 600 and 850 V tappings.
The TV line sweep valves (tubes) in the PA worked well with the lower
voltage .....but 850V was toooo much especially when you used the PI
tank for matching the antenna (no external matching unit)
I used an old 1970 era FT-400 that way as my first TRX from 1985 - 1989.

Frank GM0CSZ / KN6WH