I built this from scratch but it is acting very strange.
A. It sounds distorted unless you run it at ~85vac.
B. The louder the input, the higher the B+ goes and the lower the AC input current goes 😕
C. the output tube is running on the hot side.
A. It sounds distorted unless you run it at ~85vac.
B. The louder the input, the higher the B+ goes and the lower the AC input current goes 😕
C. the output tube is running on the hot side.
coool! OK 1st things 1st - you need to decouple the B+ to the input tube by putting a capacitor (say, 22uf) across the supply AFTER the 680 ohm resistor.
Is your PSU REALLY half wave? Thats gotta hurt!
Anyway, no input measurements please - B+ at both tube anodes, voltage drop across both cathode resistors. Measured, not calculated.
Is your PSU REALLY half wave? Thats gotta hurt!
Anyway, no input measurements please - B+ at both tube anodes, voltage drop across both cathode resistors. Measured, not calculated.
Anode voltage of the 6SN7 is 200Vdc
Testing the anode voltage of the 6V6 makes it go into oscillation.
Voltage drop of cathode resistor of 6SN7 is 5vdc
Voltage drop of cathode resistor of 6V6 is 7VDC
Testing the anode voltage of the 6V6 makes it go into oscillation.
Voltage drop of cathode resistor of 6SN7 is 5vdc
Voltage drop of cathode resistor of 6V6 is 7VDC
cool. Obviously the anode shouldn't oscillate... Whats the voltage either side of the OPT primary?
I can't find 6V6 curves yet for 420V on screen grid to select idle current then cathode resistor's value... I searched through all it's versions: 12L6, 6AQ5, 6P1P, but can't find...
Out of curiosity, where are you coming up with 420v?
There is no 420v anywhere in this amp.
There should be some 300v * 1.4 = 120V, if you rectify 300V as written on the picture.
Hi kitty - yes please, voltages at both sides of the opt primary, measured to ground. Should be around about your predicted B+
so at idle, you have 275V at the anode of the 6V6, you have about 7v across the cathode resistor, so you have 267V anode to cathode. Yes? If so, your B+ is about 90V ABOVE the RCA manual specs for the bias and load.
Next question is the oscillation...
Next question is the oscillation...
No more oscillation (caused by the meter lead to close to the grid contact).
its 265v from anode to cathode.
How do i fix it?
its 265v from anode to cathode.
How do i fix it?
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