Capacitor on Powertube Socket - Mesa Mark III green stripe

[Dr.G]

Hi everyone,
I recently acquired my first Mark Series amp, a Mark III green stripe long head that sound amazing!

While cleaning all the socket and pots I found a little plastic bag attached to one of the cable inside the amp. Inside was a 250pf ceramic cap and a note saying "250pf 1kV cap across pins 4-5 of EL34 valve".

So assuming the cap was removed I searched for schematics of the Mark III but I have not found this cap in any of them. However, I was able to find pictures of another green stripe showing this cap one the mentioned position above. Oddly enough, this cap only seems to appear on one of the EL34 sockets, the one closer to the OT.

Does anyone know, what`s the purpose of this cap?
Thanks

 

[Henz]

May be used as a fizz cap to reduce brightness but they are usually in series with the two output coupling caps ( usually .1uf 400v are the coupling caps in older Marks. Orange drops) from Phase Inverter circuit.

 

[jsullivan2112]

Hi everyone,
I recently acquired my first Mark Series amp, a Mark III green stripe long head that sound amazing!

While cleaning all the socket and pots I found a little plastic bag attached to one of the cable inside the amp. Inside was a 250pf ceramic cap and a note saying "250pf 1kV cap across pins 4-5 of EL34 valve".

So assuming the cap was removed I searched for schematics of the Mark III but I have not found this cap in any of them. However, I was able to find pictures of another green stripe showing this cap one the mentioned position above. Oddly enough, this cap only seems to appear on one of the EL34 sockets, the one closer to the OT.

Does anyone know, what`s the purpose of this cap?
Thanks

Just wanted to say congrats on grabbing a killer amp! Welcome to the club!

 

[BPMKIII]

If you find out what that cap is for please post. I have a blue stripe simu-class and am curious to know.
Cheers