Reverb Hum when turned off with footswitch

[Toxophilite]

The reverb in my stereo deluxe reverb generally works well. I haven't used the amp for a bit and as I have a show coming up this Saturday the 18th. I've been rehearsing. There's one song I use the reverb on 10 for the solo, It gives it a middle eastern sound.


I've noticed that the reverb when turned off with the footswitch has developed a loud hum. It goes away when the reverb is engaged. As I play most of the song without the reverb it's a bit of a PITA


I've been checking the cabling to the tank, tried other footswitches, swapped out the tank, swapped out the reverb circuit 12ax7 and poked around inside with a stick to see if anybody was loose.


Any ideas?

[sluckey]

Is there any hum if you kill the reverb with a shorting plug or gator clip lead inserted in the F/S jack?

[Toxophilite]

HI  S. Luckey. Long time no bug!
I've been playing with little wooden sailboats and music took a downturn during the pandemic.


Just tried a dummy plug and yes indeed it still hums  in the same way


I think it's the schematic below, However I did notice that the actual amp doesn't have a .02 cap bypassing the 220k resistor on the footswitch plug

[sluckey]

Try this...

Use a gator clip lead (or whatever is handy) to ground the middle lug of the reverb pot. This will kill the reverb. Any Hum?

If no hum simply disconnect the F/S jack from V4 pin 2 and reconnect to the reverb pot middle lug.

[Toxophilite]

That seems to work better thanks very much.  Do I leave the 220k resistor to ground on the jack?

[sluckey]

The 220K will be removed from the F/S jack. The 220K will be connected between the reverb return jack and ground. And the reverb return jack will be connected to V4 pin 2. Just a suggestion...If the reverb return jack is located next to the reverb F/S jack, you can connect the 220K to the tip of the return jack and to the ground lug of the F/S jack.

The only thing on the F/S jack tip will be a single wire that goes to the reverb pot middle lug. If this wire is more than a couple inches long, you should use a shielded cable. The shield can be connected at the F/S jack or the reverb pot, but not both.

[Toxophilite]

Will do and thanks again. It'll be good to play that song live without that hum. Also any other songs I play without reverb
This song, Frankincense, recorded in 1995 with my ultra linear super doing duty
https://open.spotify.com/track/2CXwHH8fNdaw786eNbBuNf

[sluckey]

Wish I could hear it but I'm not willing to sign up for a spotify account.

[Toxophilite]

Strange I don't think I have one either. I once made the mistake of joining this distributer (distrokid) and ended up with all my material on spotify and everywhere but making very little. Spotify really doles out the micro pennies!


Okay here it is on a different platform . Uber fender reverb in the solo
Bandcamp allows you to listen to something up to 3 times before a need to purchase, no obligation or accounts I believe
The drama of the bolero beginning makes this a good set opener
https://thecolorifics.bandcamp.com/track/frankincense