15-07-2022, 08:57 PM
(This post was last modified: 15-07-2022, 09:06 PM by Murphyv310.)
Hi.
As Michael has said the cathode voltage is correct.
The total current is well within the UL84 spec so just box it up and enjoy the radio.
Basically the test proves the valves bias is OK and you are not over running the valve.
I sometimes think that the way things are explained can confuse, I sincerely hope I've not confused you and my post was to try and make it clearer.
If the coupling capacitor was leaking badly you could have had say 25v or more on the grid pin, then I'd have worried, half a volt is acceptable and due to the 470 ohm cathode resistor it will ensure the bias level will be OK. Like I said a 220 ohm resistor in the cathode circuit would have increased the current considerably, the cathode volts would have dropped and the relationship between grid and cathode would make that negative volts more positive thus turning on the valve harder and upping the current, then the valves life would be shorter and you risk burning out the output transformer. All is well with your radio so you can sleep in peace tonight.
Enjoy
As Michael has said the cathode voltage is correct.
The total current is well within the UL84 spec so just box it up and enjoy the radio.
Basically the test proves the valves bias is OK and you are not over running the valve.
I sometimes think that the way things are explained can confuse, I sincerely hope I've not confused you and my post was to try and make it clearer.
If the coupling capacitor was leaking badly you could have had say 25v or more on the grid pin, then I'd have worried, half a volt is acceptable and due to the 470 ohm cathode resistor it will ensure the bias level will be OK. Like I said a 220 ohm resistor in the cathode circuit would have increased the current considerably, the cathode volts would have dropped and the relationship between grid and cathode would make that negative volts more positive thus turning on the valve harder and upping the current, then the valves life would be shorter and you risk burning out the output transformer. All is well with your radio so you can sleep in peace tonight.
Enjoy
