On 28 Ago, 13:11, cliff wright wrote:
Geoffrey S. Mendelson wrote:

The tubes in Question are a pair of 6883B's. According to all my data
they are identical to the 6146B except for a nominally 12.6 volt
heater rating, and a tiny increase in interelectrode capacity (about
1%). They were often used in high power (~60 watt) HF "bush" radio
telephones in NZ until recently, both in SSB and AM modes.
So they are relatively common here.
I pulled the covers off the final to check after your posting.
Since the 820S actually runs the 6146B heaters in series from 12.6 volts
there should be absolutely NO reason why they couldn't do the job with a
simple heater rewire from series to parallel.
They are physically identical to a 6146B externally.

Indeed the 6883B is like a 6146B with different heater voltage. Then
either these tubes are bad or you have another problem on your radio.
Check antenna TX/RX relay and antenna socket connector. I had an
FT-102 with antenna socket with an intermittent solder joint and it
caused all sort of problems. It seems that you already checked all
voltages on the tubes, but it might help to know what you exactly
measured on the various grids and anodes, both in RX mode and in TX
(idle). Do you observe any variation on the idle current of tubes when
in TX mode with no mic input? When these tubes fail usually they have
an ever increasing idle current and there's little to no way to stop
this current to increase.

73

Francesco IZ8DWF