• 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.

Valve PA amplifier - what to do with it?

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Can you confirm the voltage drops of 8.12 and 8.19V relate to the voltage from output transformer primary mid-point, out to each anode? Or is that the drop across each seperate anode stopper, which post #80 indicates are 100 ohm. Perhaps good to repost the schems with updated corrections, to avoid having to dig through 9 pages of posts. PS. I just saw your schematic and they are shown as 100k - need to be careful when reviewing details!

If it was 8V across 100 ohm then that is 80mA per plate, not 116mA, as per post #145, but still way too high I think.

I can't identify if you measured the dcc resistance of the output transformer half-primary windings, although in post #144 you note that (I presume) one of those half-windings has a dcr of 9 ohm less than the other half-winding (it is quite expected to have a difference in resistance, as that indicates the windings are wound on different layers).
 
Can you confirm the voltage drops of 8.12 and 8.19V relate to the voltage from output transformer primary mid-point, out to each anode? Or is that the drop across each seperate anode stopper
Literally measures across the 2 separate resistor, Trobbins.


. I just saw your schematic and they are shown as 100k - need to be careful when reviewing details!
These were both replaced as one had drifted.

Updating the whole sketch and will repost it asap
 
Measurements should tally fairly closely when you add up the currents into each anode, and the two screens, and compare that sum with the total current flowing through the common cathode resistor. If that is all ok, then need to calculate the anode-to-cathode voltage, by subtracting off the cathode and anode resistor (including OPT winding resistance) from the total B+ provided to the OPT CT, to get the voltage and current values to use for calculating EL34 dissipation.

Do you only have two EL34 to play with?
 
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