Strange noise with Einstein 50

[Simop]

Hello and greetings to everybody from a newbie!

I'm having some trouble with my dear Ein. It started to buzz and produce lot's of noise a couple weeks ago. As long as I can remember nothing strange has happened, ie I haven't peed on it, poured in beverages, smashed it with a hammer etc. Strangely the whole ruckus stops the same instant I unplug my cord from input. The problem isn't my cables or guitars that's too obvious even for me.

Tomorrow I'm going to replace my powertubes with original one's and I'm hoping it solves the problem. Anyhow it would seem pretty strange as there's almost no noise at all when nothing is plugged in. Any ideas?

If it help's somehow, here's my signal path: guitar --> Einstein --> cab. Keepin' it simple.

 

[steppenwolf3080]

I think it could be a preamp tube gone bad. I had similar problems with another amp and it turned out to be a noisey pre tube. There seem to be a rule that 80% of problems with tube amps can be located at the tubes themselves...(That's why I always have some 12AX7 on stock;-))

By the way:
The fact that the noise is gone when you unplug the guitar cable from the amp isn't strange.
I noticed that the noise Eini (normal white noise on high gain) puts out is cutted off when I unplug the chord. That is an indication that theres is some circuitry connected to the input jack that mutes the output somewhere in the signal path (pulling down signal to ground by relais, opto ...) to avoid unnecessary noise when not actually played.
So maybe the noise emmited by probably a bad pre tube is also cutted off. If my theory is right, that would exclude the power amp tubes causing the problem, as it is unlikely that the signal is muted after the power stage. Just my 2 cents, though.

You'll fix the problem!!

Greets,
Stefan

 

[Simop]

Muting something... Too damn clever for me! Look's like I'm also bringing in my preamp tube collection tomorrow.

Thanks!

 

[steppenwolf3080]

Jes, muting. When nothing is connected to the amp, the signal is interrupted somewhere inside the amp if that is easier to understand . Put out V1 and replace it, if that doesn't work, go on till you find it.