5e9 tremolux cutting off when switching tremolo off

[lulin]

hi all
i ve just finished to built a 5e9 tremolux. sound great .only a problem. if i switch the tremolo off using the foot switch with the depth from 4 o clock (9) to max the sound cuts off. the tremolo works all the way.

I ve built this amp from scratch following fender original layout and shematic.5E9-A

the circuit is standard appart from adding a negative feedback loop and i ve also added a couple of 470ohms resistors to decouple the screens of the power tubes.

i ve fitted the 10 meg resistor between B+ and trem jack as shown on 5e9 layout.
for the negative feedback I added a 56 kohms resistor from output secondary on speaker jack to cathode of second preamp valve(pin 3,which is bridged with pin 8 . pin 8 linked to cathode bypass cap and to depth control..I' ve disconnected the feedback loop and the problem is still there..I've measured voltage on V2 pin 3 : 2.6 volts but when I turn depth up to 3o'clock i get 3.1 volts and the volume start to go down a bit
turning to 4 o'clock i get 3.9volts and the volume dropped a bit more
turning to 5 o'clock I get 4.7 volts and no sound...
the pot is a250k and the the resistor a 100k .I ve 71.9 kohms when depth turn all the way up, across 100 k resistor which seems normal and i double check is where it should be..
any idea ?
thank you!

[tubeswell]

Hi lulin and welcome to the forum

I have said this elsewhere but the oscillator's cathode follower should not cause the bias at the PI to go permanently into cutoff when the intensity increases

Where is your NFB looped back to? and have you tried disconnecting the NFB loop?

Otherwise I suspect its probably a wiring error.

[loudthud]

First of all, disconnect the feedback. The way you have it connected won't work properly.

I would try increasing the 100K resistor on the depth control. 150K or 220K should make it so the signal won't be cut off completely. When you control is set past 4 o'clock the guitar signal is probably just pulsing on and off. That might be a cool effect but not what was intended for this amp.

[lulin]

hi thank you very much for your advises. I ve disconnected the NFL and replaced the 100k for 220k and that has sorted the problem .so thanks again for your help. And i ll keep checking out the forum as I ll be learning a lot it seems.