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I am experimenting with a 45 SET amplifier circuit as follows:
6SN7 driver with interstage transformer secondary to the grid of the 45, 1.35K bias resistor and 25MFD oil capacitor in parallel to it from the cathode to ground...the filiment connected to the typical hum pot arrangement. The plate is connected to a 3.5K Single ended output transformer. The question is that I have 310 to 320 VDC measured at the plate of the 45 to ground. The amplifier plays fine. Is the B+ too high to be safe for this tube? I notice no "red plate" glow and there is no distortion. Thanks for your input.
Follow Ups:
Who many milliamps are you getting from the 45 at your current voltage?George
Assuming typical bias as applied thru the cathode resistor, plate VDC to ground is fine business. I guess about 50 volts across the cathode resistor, thus the tube would measure 260-270 volts from the 45 plate to the filament. In other words, 260-270 volts is all the tube 'sees'. Perfect!
Typically yes.
However if your not biasing the tube above its rated current you will be ok..My se811 amps use a 6l6gc driver which has 650 on the plate but being its only set up to pull about 24ma or so,it doesnt hurt the tube.
Bassed on the information I gave, should the current be ok? The RCA book says 275 on the plate...
Mike
Do what pete said or easier yet just measure the voltage across the cathode resistor and divide by the cathode resistor and make sure it doesnt exceed the rating of the tube.
What's the voltage across the 1.35K cathode resistor? The 275V spec is the voltage at the plate with respect to the cathode. With ~310V on the plate with respect to ground, I suspect that you are just fine. Just check your cathode voltage and subtract that from the plate voltage.Take care.
Pete.
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