Framus CS

[Simpson]

Hi!

This amp came making some crackling noise and I thought it was some preamp tube.
In fact, when I pull the reverb tube, the noise goes away, so I have replaced the tube ( 2 times ), but the noise continues.
I have the reverb cable disconnected and the switch off.
Even with a new tube socket the problem remains.

What should i do next?

[xtian]

If noise vanishes when you pull V5, that implicates the supporting components R30-33 and C16,17. The plate resistor R31 would be my first suspect.

[Simpson]

Thank you for replying. I'll check these parts.

I also notice very small DC on the grid, 50mV, could this be the cause?