Weak and crackling sound

[Leevi]

The sound is is very weak and it's crackling. I measured the voltages on PI pins 1 and 6.

1: 166v
6: 250v

I'm just wondering this big difference but have not found any good reason for it.
Heaters have been cheked and I have tried with another tube.

http://www.kolumbus.fi/~y635749/RikstoneAmps/PowerAmpC15b.pdf

The amp is very simple, one EF86 as a preamp.

Leevi

[stratele52]

Check all Power Supply voltages

[sluckey]

"Crackling" can sometimes be caused by plate resistors, especially when using carbon comp resistors.

Weak? This is just a power amp and requires about 1 V_rms to drive to full power. You're not trying to plug your guitar straight into point C1 are you?

[Leevi]

This is just a power amp and requires about 1 Vrms to drive to full power. You're not trying to plug your guitar straight into point C1 are you?

I just added the schematic of the power amp. There is EF86 + 6 pos cap. switch + volume
before PI. I have checked the signal level after preamp and it's OK.

/Leevi

[Leevi]

There was cap missing between volume and PI input.
Now at least the plate voltages are in balance but there are still some
oscillation problems I have to fix by changing the wiring.

/Leevi