the 6L6 beam tetrode hit the market around 1936 and soon after the works
were packaged in a glass envelope with top cap and a 5pin base for RF use
and designated 807.
II recall a bit of interest in the 50th anniversary of 6L6 and 807 around
1986, guys buillt retro txs on breadboards using the tubes.
BTW 6L6 also came out as a metal tube, and a variety of glass envelopes.
Do not know when the 12v filament 1625 military version appeared. Think it
would have been prewar. Think the ARC-5 receivers were in production mid
1930s, presumably the Tx that used 1625s late 30s.
807 variants I have met:
The British type with ceramic base and British 5 pin base.
Philips Dutch Q ----- version.
The small envelope octal based version 5B254 ? that appeared in the late 40s
or early 50s.
The Brits had a similar beast with a loctal base.
With the advent of TV the 6L6 was repackaged as a sweep tube ?6BL6 with top
cap making it an 807 variant, I guess.
Think this came out with a variety of heater voltages for use in series
Post WWII 807s were available cheap as mil surplus, 1625s even cheaper.
So long as one treated the screen kindly they seemed to last forever.
Back in VK and ZL when we were limited to 100watts input it was not unusual
to see 807s in class C with 1000v or more on the plate, loaded to 100W in no
Also widely used in AM modulators and audio amps, sometimes triode
Barry Kirkwood PhD ZL1DD
Amps mailing list