Marshall Silver Jubilee 2555X no sound problem

[Pepperman]

Hi all,
I have a problem with my Marshall Silver Jubilee 2555X.
The symptom is that if I play silent everything is OK and sound is hearable, but if I hit the strings hard with a high dynamic the amp mutes quite right away and no sound is output anymore.
The situation is not self recoverable, but it is solved when I unplug the input (I guess the shorten of the input pin to GND) sound is hearable again.
It is 100% reproducible.
If I input the signal to the return input this issue does not appear.

Can anyone help me on that?

I attached a video of this.

Thanks

 

[Pepperman]

Any hint? It would be great

 

[FleshOnGear]

How long has it been doing this? Are you using active pickups or any pedals before the amp’s input?

The best guess I have, based on the info you’ve given so far, is that your input tube has gone bad. Maybe its grid is pulling a bunch of current, building up a negative charge on the input capacitor (assuming the 2555x has one - I think the original 2555 does). This could shut off the tube. Maybe the larger signal triggers this.

Have you tried swapping out preamp tubes?

 

[Pepperman]

Thank you very much for your reply!
I bought this used amp a couple of weeks ago 2nd hand, so unfortunately I dont know whether this was a known issue.
I use several pedals in the normal input, not effect loop, yes! But no active pickup.
Today I tested swapping the preamp tubes, I have 2 new JJ ECC803S gold types and did the following tests.
1. replaced 1st input tube (with metal case) with new JJ ECC803S -> sound cut off happened with large input signal
2. additianally replaced 2nd input tube with new JJ ECC803S -> same thing
3. exchanged third tube with old 2nd tube -> same thing happened (maybe a bit higher input signal needed, raised Micro Amp)

The effect loop consists of several pedals with Micro Amp -> DS1 -> DS2 -> Big Muff -> Ibanez Wah WH10v3 -> Boss CE1

It especially happens with activated WH10v3 which does increase the signal amplitude and also with Micro Amp.

Could it be a bad solder joint, tube socket, or cap?

Thanks for any advice

 

[El Gringo]

Try playing straight into the amp in the front with no pedals just your cord plugged into your guitar and amp and see what happens .

 

[Pepperman]

I tested it with only the guitar directly connected to the amp and the same thing happens also

 

[PentodeLicious]

That is very strange.
AFAIK this amp does not have a mute circuit, that would be my first guess.
We know it is in the preamp section because the return input works fine.
Maybe one of the clipping diodes/leds gone bad?
And then it shorts to ground instead of clipping the signal.
Does this happen in the clean channel without the rhythm clip pulled?