Fender footswitch: problems replacing old RCA plugs with one stereo 1/4" plug

[bram9206]

Hi,
I have here my old 1972 Fender Deluxe Reverb and I got a bit tired of resoldering the RCA plugs every 10 gigs, so I decided to replace the RCA plugs with one stereo 1/4" jack (just like the reissue fenders).

Took out the (reverb-side) RCA female and replaced it with a stereo 1/4" female. Then soldered the reverb to tip and vibrato to sleeve. There is also a capacitor that goes to the ground of the former vibrato RCA plug. Here is a pic, not mine though:

But since it simply goes to ground I left it there at the ground of the "former" vibrato RCA.

Seemed like a perfect fix, but I have two problems:
- there is a loud click sound when I push the vibrato knob. It's not always there, sometimes I push it five times and I have no click at all, then I click it another five times and it's there... unpredictable, but it wasn't there before.
- when I turn up the reverb there is quiet some hum that was not there before the "fix"...

Anyone any idea? Can I actually just replace the RCA jacks with a 1/4" jack? Or did I overlook something? Why is there a cap at the ground of the vibrato RCA? Because I can't find it in the blackface models...

Thanks a lot!

 

[bram9206]

Ok, this is where I'm at: I changed the 1/4" plug with a decent plug (not the ones used by Fender for their RI footswitch) and the noise/hum in the reverb went away. So that problem is solved!

But I still have this loud "click" sound when I push the vibrato switch. Here's the problem in detail: when the reverb is switched OFF and I push the vibrato their is never a click sound. So in this case the vibrato can be switched on and off without any noise...
But when I switch the vibrato on and off with the reverb switched ON I always have the loud "click" noise!

Does anyone have any idea what could be the problem here? I'm a bit surprised that it's so hard to change the RCA plugs to one stereo 1/4" plug... Then how is it done in the reissue Fenders?

Thanks!

 

[limbe]

The lead to the reverb pedal goes straight to the grid of the tube that is connected to the reverb units output.In other words to the tube that is there to amplify the weak signal from the reverb units output.I am guessing the "click" from your vibrato switch is entering the grid of the reverbs return tube by induction.Does the "click" get louder if you set the reverb knob higher? To answer your question:They use a 1/4 stereo plug with one difference,the lead for the reverb is not connected to the grid of the tube,it is connected to lug no.3 of the reverb control.The signal is much stronger here and not sensitive for switch-clicks.The vibrato circuit is also a bit changed.

 

[limbe]

What I started doing about 15 years ago,was to try to avoid soldering RCA plugs and 3.5 mm tele jacks.It is nearly impossible to avoid something breaking if you pull at the cord.
Instead I use ready-made cables with those two connectors at one end and simply clip off the connectors at the other end.You could (and maybe would have if you know what you know now) have bought Hi.Fi cables with Rca plugs which would last forever.

 

[bram9206]

Thanks for your reply. I just tried and yes, the "click" sound does get louder when I set the reverb knob higher. What does this imply?

 

[bram9206]

By the way, here are some pictures I took this afternoon of my Deluxe Reverb and the 1/4" mod I did. Maybe this helps locating the problem? I already pushed the green and yellow wires to the amp's chassis, away from the heaters, just to be sure. Doesn't make much differece though and doesn't affect the "click" problem...

 

[limbe]

Guess I was unclear when i wrote that I thought the "click" from the vibrato switch entered the tube for the reverb return.That is because the leads are so close now.
The fact that you write that it gets louder when you turn up the reverb confirms my theory.Fender solved the problem by redesigning the circuit of the reissue.Let me state this first.There is nothing wrong with your amp.There is no problem to locate.The only thing that has happened is that you put the vibrato and reverb lead in the same jack and plug which has led to that noise from the vibrato enters the reverb channel.The simplest solution is to separate them again.If you change the vibrato pedals jack to a 1/4 " mono jack you can connect it to the vibrato lead .You can leave the reverb lead soldered to the tip of the 1/4" jack and solder the sleeve to ground.I assume you had to make the hole bigger for the 1/4 " jack which probably has devalued the amp.Being no expert I don´t know how much but I don´t think one more hole will matter much.If you are determined to just have one jack,you must do what Fender do,change the circuit.

 

[chris m.]

I'm no expert, but that sounds right. When you had two RCA plugs, you had two different hots and two different grounds, and the two separate grounds were probably wired to different places in the amp, with a cap or something somewhere on one of the ground points to prevent popping. When you put in a stereo plug, you still have two separate hots, but the separate grounds ended up being combined together and going to ground into the same place. If you went with two 1/4" mono plugs, then you could restore the original wiring scheme and the pop would go away.

 

[TheSmokingMan]

Inductance isn't the issue. The issue was hit upon when figuring out that A) the cap wasn't wired in, because it needs to be in the switching circuit for the vibe. B) the return signals of the reverb and vibe switches can't be on the same wire because they do go different places in the circuit. If your amp is going to remain your amp and function is more important than form then ditch RCA for mono 1/4 jacks(non shorting, isolated)

 

[limbe]

Yes,if you change the RCA jacks to 1/4" jacks and wire them the same,the click should disappear because it wasn´t there before the original wiring scheme was disturbed.

 

[TheSmokingMan]

..

 

[limbe]

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