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Welcome to the Marshall amp forum Roger :cheers:.
The output tube screen resistors should be tested. If these resistors are out of spec it will...
You said: the Foot Switch issue does not happen when you use TAD / JJ tubes?
Is that correct?
From what OP wrote, the FS issue does not happen when he uses different preamp tubes.
That's what I got from reading it anyway.
“1 more tweak”.
The bias voltage is turned on before the high voltage is turned on.
This decreases surge on the output tubes, as the high voltage...
Swap out Sovtec LPS one at a time with a JJ or TAD tube.
Re-test the amp each time you swap one LPS out.
There is probably one bad LPS tube which...
You should read: "how to keep your Volkswagen alive, a guide for the complete idiot."
This is a continuation of : "Zen and the art of motorcycle...
Just checking because many of these amps were 6550 from the factory.
And sometimes people try to put EL34s in an amp that is set for 6550 and it...
Yes if the output tubes are out of balance it can make the hum show up at the speaker output.
Another thing is if one of the PI plate resistors is...
There is actually dual analog op amps that have an A/B switch built into the op amp.
The A/B switching is controlled by a voltage from the...
OK so the amp is set for EL34.
Take the reverb tank out of the amp.
Look inside the reverb tank where the wire are soldered to the RCA jacks.
Is there a broken wire right at one...
Turn on the amp.
Turn up the reverb and master volume controls.
Un-plug the reverb return from the reverb tank.
Touch just the tip of the reverb...
Brian Jones, of Rolling Stones? Are you the Ghost of rockstars past?
Turn up the reverb control, turn up the master volume shake the amp around...
OK do one more thing before I fall asleep.
He likes it super clean w/ external Fender reverb unit. Lots of mega - surf reverb.
Your'e right it may be worn out should read 250K.
50% out of tolerance.
Test the wire on V3 socket pin 8 that leads to the circuit board 100K resistor. Make sure that wire reads 0 from end to end.
test all the interconnection wires in the circuit and make sure they all read 0 ohms from 1 end to the other end.
Test the violet wire and make...
5. Connect ohm meter across terminal 1 and 3 of the bass control.
Rotate the bass control slowly up and down.
Reading should be 0- 1 meg ohms....
Don't hook the red cap back up yet, don't hook the violet wire back to the treble pot yet.
Test across the treble pot from terminal 1 to terminal...