5F6A low volume

[Helmholtz]

V3
pin1 271
pin3 18
pin6 375
pin8 18

Seems we still have the same problem as discussed before the socket change. As already mentioned, the high plate voltage at pin 6 (as well as the low common cathode voltage) mean that one of the triodes is not conducting current. (Its a double-triode having 2 separate heaters. One is internally connected to pins 9 and 4 , the other to pins 9 and 5. By jumpering socket contacts 4 and 5 the heaters are wired in parallel.)
If only one of the triodes is operative, this results in low output and hum.

Can you check that both filament wires are glowing?

I suspect a socket wiring error/problem, especially regarding heaters. Can you check heater voltages between pin 9 and pins 4/5.
Please check socket jumper connections between pins 4 and 5 as well as between pin 3 and 8. Also any wires shorting?

[Chuck H]

Seems we still have the same problem as discussed before the socket change. As already mentioned, the high plate voltage at pin 6 (as well as the low common cathode voltage) mean that one of the triodes is not conducting current.
Can you check that both filament wires are glowing?

I suspect a socket wiring error/problem, especially regarding heaters. Can you check heater voltage between pin 9 and pins 4/5.
Please check socket connections between pins 4 and 5 as well as between pin 3 and 8. Also any wires shorting?

vinceg's reports indicate that this voltage condition only happens with one of his preamp tubes and not others and that it was that tube that was in the amp when these last voltage readings were taken.

[nosaj]

vinceg's reports indicate that this voltage condition only happens with one of his preamp tubes and not others and that it was that tube that was in the amp when these last voltage readings were taken.

Dumb question. Is it always the same tube in that socket or does a differsnt tube give roughly same data?

nosaj

[vinceg]

Update

Heater problem is resolved, the cause was fuse holders. I noticed that moving heater wires pilot lamp went out. Now I've wall voltage of 230V and heater voltage of 6.1V

Also I change the tube and now amp has right volume. I'm surprise to note how tubes are bad

Hum remain to be fixed.

[vinceg]

Dumb question. Is it always the same tube in that socket or does a differsnt tube give roughly same data?

nosaj

Believe me, I got confused. I think that tubes fall down because low heater voltage

[Helmholtz]

Update

Heater problem is resolved, the cause was fuse holders. I noticed that moving heater wires pilot lamp went out. Now I've wall voltage of 230V and heater voltage of 6.1V

Also I change the tube and now amp has right volume. I'm surprise to note how tubes are bad

Hum remain to be fixed.

Please update V3 voltages.

[vinceg]

Please update V3 voltages.

Now it is correct

V3
pin1 255
pin3 41
pin6 252
pin8 41

[vinceg]

Update

It seems that the cause of the hum is heater wires. I got up heater wire from V2 with a chopstick and hum has significantly reduced but not completely gone.

What can I do to get better? Are they too close to signal wires? Can Heater elevation resolve?