Hi Carl,
-
There are some Commercial and Amateur RF Amplifier circuits
where the tubes are cut off in standby (receive) using rectified
heater voltage or a developed drop through a high value
resistor. Depending on how you measure it against ground,
12 volts control grid to cathode could be enough to cut the
tubes current back in standby, developed by a few different
methods (circuit approach).
-
In Tx mode, the tubes would come out of cutoff (or
reduced current flow) into normal AB2 operation and the
~7 volts value doesn't seem to whacky for certain circuits
I've seen using sweep tubes.
-
No "direction" of the bias voltage was given, but the
person could have meant -12 volts in standby to
~7 volts in Tx mode.
-
Email me direct if you need a specific example.
-
cheers
skipp
-
Chomping at the bit for Dayton...
-
-
--------- Forwarded message ----------
From: "carl seyersdahl" <carlseye@tampabay.rr.com>
The other day I questioned a person about the bias on an amp he sold!!
this
was agla1000 with EL509's.. he stated that the the bias was 12 v. at idle
and 6.9 under full power! this certainly doesn't seem right to me , or am
I
missing something??
I was taught that the bias for a class a- ab1-ab2 -b amp should stay the
same at all times... Have times changed or the technology changed? Or
have I
forgotten something after so many years???
carl / kz5ca
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