Reverb knob is not properly works. Help!

[psychepool]

I made deluxe reverb clone

Precisely, It is AX84 California Dreamer.
http://home.comcast.net/~daniel.souder/ ... tic_V3.pdf
It is the single channel deluxe reverb with no vibrato.


The problem is reverb knob.
It operates normally, until the knob sets to half.
But when the knob sets over half, it doesn't work.
No guitar signal. Only get hum noise .


The original tank is 4AB3C1B.
But I use 8AB2C1B because no room for long tank in my head cabinet.
These tanks have little different Impedance.

4AB3C1B
input : 8ohms
output : 2250ohms

8AB3C1B
input : 10ohms
output : 2575ohms

Is this difference causes the problem?
I have not found the wiring problem, And voltage is also fine.

What should I do for properly working reverb?

[martin manning]

The impedance differences you list are not significant. Perhaps the pot is defective? Try shorting the center lug to the clockwise lug when the knob in a position where the signal has cut out.

[psychepool]

Thanks Martin, I will try it!

Note : I use Audio taper 100K pot for reverb knob. Not Linear taper.

[pdf64]

Yes, an audio taper seems more appropriate for this; it shouldn't cause a problem.
If it isn't just a bad pot, check the V4 cathode voltages in the good and fault modes.
I'm thinking that V4 may be going into oscillation, when the cascaded gain between pin 2 grid and pin 6 plate becomes sufficient.
Grid stoppers / improved lead dress may help with that issue.