Cable for Fender footswitch?

[pikingrin]

I got a used Fender Twin about 2 months ago that came with the footswitch and all the docs, etc. It did not come with a cable to connect the footswitch to the jack on the back of the amp though. As it stands now, I've tried a regular instrument cable (TS) and a balanced (TRS) cable. I'm wondering if there is a special cable needed because on the footswitch there are 4 switches: channel 1, channel 2, reverb and tremolo. Only the channel 1, channel 2 and reverb switches do anything. The 4th switch doesn't even light up when pressed and it doesn't activate/deactivate the tremolo. Is this possibly a footswitch issue or am I completely missing something?

 

[ido1957]

Try a speaker cable

 

[ecc83]

AFAICT it is a simple two pole TS jack so a conventional guitar lead should work.

There might of course be variants or the F/S could be faulty!

Dave.

 

[pikingrin]

Below is the schematic showing a portion of what I believe may be your amp. A TS type plug would be correct for the footswitch to operate. At a guess I think the problem is within the footswitch. There is 26vac through a resistor that supplies the the power to the footswitch and this seems to be present as the other three switch functions appear to work correctly. The switch for the Tremelo may not be opening to allow voltage to pass the rectifier/blocking diode to illuminate the Red Tremelo LED or either the Red Tremelo LED or series diode may be open which then doesn't allow the control voltage to the amp change the state of the tremelo control circuit. Does the tremelo switch have a definite click like I think the other switches when depressed would have or just a spongy soft push and no click?
If you have a multimeter, either digital or analog and have a basic idea how to check resistance and voltage you might be able to identify the problem. Might be able to walk you through some checks if you have a meter.

The reverb and channel switching circuits actually have small relays to enable these functions. The tremelo is controlled by (TREM_MUTE) and an FET transistor that changes the bias on the tube that generates the tremelo waveform.

The tremolo button clicks like the rest in the FS do. I'm wondering if it may be just an issue of a tremolo that isn't switchable in this amp paired with a one-size-fits-all Fender FS. Either way, I have both an analog and digital meter so I can check voltages if I know where the test points are and what to set the meter to...

 

[mjbphotos]

You do have the termolo knob on the Twin turned up, don't you? Pretty sure this is only on Channel 2, as well.

 

[mjbphotos]

That's possible, on my old Fender amp the reverb and tremolo were only the 2nd channel, the first one was the bare bones one.

 

[pikingrin]

You do have the termolo knob on the Twin turned up, don't you? Pretty sure this is only on Channel 2, as well.

The tremolo is applied to both channels on this amp; I've tried messing around with the level to see if that affects the FS operation and it doesn't change anything. All in all, I'm really satisfied with the amp just wish I had the functionality of that FS button...