Radio interference coming through the reverb

[LooseChange]

I have been working with a Fender Prosonic that picks up radio when the reverb is turned up.
We have tried all the basic stuff like ferrite chokes on the reverb send, return and footswitch cable with no luck. Changed the tube too.  No luck.

The owner contacted Fender and their only suggestion was the ferrite choke or get another Fender.

Any one have a thought on this??

Thanks!

[FYL]

If the symptoms are still present w/o the FS:

- Clean all plugs and sockets with Caig Deoxit or similar
- Change the reverb cable for a better shielded model
- Add 10K grid stops to V5a and V5b
- Replace the green wire between the reverb section and V6b by coax, with shield connected only to V6b

You may also try a mains RF filter.

[jjasilli]

Other possibilities:

*  use a listening amp to track down where the RF is first appearing.

*  disconnect signal in & out of this reverb amp section from the rest of the Prosonic; and run a sine wave through the standalone reverb amp.  Is there still RF noise?

Is it possible that RF is appearing at the amps's input jacks, e.g., but becoming audible only after extra amplification in the reverb amp?  Is there RF noise with no guitar cable plugged into the amp?

[kagliostro]

Radio Frequency can have hidden strange interactions

here in Italy few time ago we had the case of an handicapped person sitting in a wheelchair

every time she entered in a supermarket the alarm go on

a pull of experts examined for some time this case

at the end the problem was on the wheelchair

and was solved moving a screw present in the wheelchair of few millimeters

Kagliostro

[LooseChange]

When the reverb is turned off the RF stops.  The RF diminshes a little when the foot switch cable is removed.

[kagliostro]

have you try to put a ferrite bead in the input of the foot switch and in the reverb signal path ?

at last you can also try to change the reverb tank

if you have one

that only as to try if the problem comes from the reverb spring lenght


EDIT >> I forgot

have you think to cover the inside of the amp case with aluminum film (the same you use in the kitchen) and connect this shield to the ground ?

Kagliostro

[FYL]

OK, I'd focus on the reverb input/driving stage.

[jjasilli]

OK, I'd focus on the reverb input/driving stage.

Agreed. And much of the stuff I mentioned before, though maybe more specific, would probably be cured by FYL's prior suggestions.