Then If let him warm up for let´s say 10 min this seems to fix the issue... Who is the culprit here? bad solder joints?
It is strange that you can actually play the guitar. It seems the guitar and the noise are in in different channels.
This amp has been kept sitted for a long time since I use my Blues Jr 95% of the time. I remember somebody here saying that these amps don´t like to be kept turned off for a long time....
Another possibility could be a intermitent component but I was told that this doen´t exist. Anyway thanks for the input. Maybe it is time for a complete revision on sockets, solder joints etc...