Perhaps it's breaking into oscillation?
73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
On 24/05/2023 15:20, Ken Harada wrote:
Hi Amp enthusiasts,
I am building a HF linear amp with 2 x 4CX350A with cathode driven
circuit, but getting a strange symptom. Ep=2000V, Esg=300V (regulated
with Zener and FET), Ecg=-50V to -20V (by LM337SP). Before applying any
RF, I try to adjust no signal anode current by varying the Ecg. Going
up from -40V, it gradually increases from 0 to approx 50mA, and in a
sudden it jumps up to 300mA (around at -30V). Moving back to deeper
Ecg, it remains 300mA and suddenly drop to 0 - showing hysteresis.
I wonder what is happening to the tubes/circuit and where I should
check. Any suggestion would be greatly appreciated.
Regards,
Ken /JO1VRK
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