20-07-2020, 06:35 PM
(This post was last modified: 20-07-2020, 06:38 PM by Murphyv310.)
Hi.
The voltages are just about fine. The grids are a little low but that is due to the internal resistance of your meter. The dropping of the one voltage could be due to the anode load resistor changing value, valve warming slow etc but again not a reason to induce hum.
The only other thing I can think of that is a genuine fault would be the last HT smoothing cap C2, 15uf that I have already said could be the problem. It may be open circuit or have a bad connection. Do you know how to bridge a smoother? if you do then a 4uf or above will do for a test just make sure its 250 volt working or above. If you are not sure please come back and ask for instructions.
Do the smoother first then if the same we need to see the scope on each of the V3 valve anodes.
The voltages are just about fine. The grids are a little low but that is due to the internal resistance of your meter. The dropping of the one voltage could be due to the anode load resistor changing value, valve warming slow etc but again not a reason to induce hum.
The only other thing I can think of that is a genuine fault would be the last HT smoothing cap C2, 15uf that I have already said could be the problem. It may be open circuit or have a bad connection. Do you know how to bridge a smoother? if you do then a 4uf or above will do for a test just make sure its 250 volt working or above. If you are not sure please come back and ask for instructions.
Do the smoother first then if the same we need to see the scope on each of the V3 valve anodes.
