WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
i'm measuring 355 volts at the plate of the 2A3 tube. the cathode resistor is 3k. i cant quite remember the cathode voltage but i computed the bias current at around 55mA and a plate dissipation of 9.6 watts. what i would like to know is that is it ok for the plate voltage to be 355 volts when anode voltage should be 250 Volts only for 2A3 tubes? or should i subtract the cathode voltage to get no more than 250 volts? another question is will the sovtek 2A3 not be able to handle plate voltage greater than 250 volts?
can u suggest what cathode resistor value be more appropriate to increase plate dissipation? i can only buy resistor values up to 10 watts so please suggest what values i can connect in parallel or series. thanks a lot.
sorry but i dont know how to post schematics. but its very similar to the Black Art Audio direct coupled 2A3 with 6dj8 driver in srpp. the differnce is that i hav 355v b+, 3k cathode resistor for the 2A3. as for the driver tube, voltage dropping resistor of 4k then 10 k anode resistor. all the values of the rest is almost the same as the black art schem.
i measured the plate voltage of top 1/2 of the 6dj8 at 260 volts. i dont know if i need to drop this at srpp circuit. any help from you or any of the good guys here will be appreciated very much.
i guess not. you lower your cathode resistor, you pull more current, which means your B+ is going down even further.
Why are you so stuck with this power supply? What's the transformer secondaries? What's the filtering topology? (CRCRC, CLCLC, LCLC, etc)
If you're stuck with that power transformer *and* using tube rectification, ditch the tube rectifier and use SS. You will get a higher B+
it's just not enough... if the 2A3 grid is 130V from the SRPP, you want the cathode to be 45V above that, 175V. 175V / 50mA = 3K5 ohms cathode resistor. But you actually need 4V + 130V + 45V + 250V = 430V
my filtering section after the 5u4g tube is composed of 20uf cap then 10H choke then 220uf cap which gives me a b+ of a little over 350volts. will changing the caps give me a higher b+? sorry but im just a newbie. and thanks for the reply.