Help: Marshall Chanel/ Reverb switch mod

[Berti]

Good evening,

It's my first post/ question.

I got a Marshall JCM900 and a Marshall double footswitch I originally bought many years ago for a different amp I don't use anymore.

My plan was to use the footswitch to switch between channels and reverb. Therefore it just needed a little rewiring I did according to a schematic I got from the originally JCM900 footswitch.
That worked very well and all functioned as it should be. My next step was to add LEDs to the circuit and that was where my problems begun.

I looked up a tutorial and build in the LEDs/ resistors as it was shown there. Since the amp signal for channels and reverb had differing outputs I had to use different resistors (used the same LEDs though).

After I finished the Channel switch worked just fine including the LED but the reverb won't work anymore (the LED does). I anticipated that the resistor I was using maybe was to strong so I used different weaker ones until the last one I tried had just half of the recommended value - but nothing changed.

Are there any suggestions what I've might done wrong?

The values are (approximately):
Channel switch output: 16A
Calculated resistor: 680 Ohms
Reverb switch output: 23A
Calculated resistor: 1000 Ohms

Many thanks in advance and sorry if I didn't got all the words/ grammar right, English is not my first language

[willienillie]

Can you share the schematic(s) you worked from?

[Berti]

I used a scematic similar to this one:
https://www.tubesandmore.com/sites/default/files/associated_files/p-h471_functional_diagram.png

Here is a picture of what I did before I added the LEDs - when it still worked.
green is gound, brown is channel and white is reverb:

https://ibb.co/FYVtJHK

Thanks and best regards
Berti

[willienillie]

How are the LEDs powered?

[Berti]

The voltage comes from the amp, there is no extra power source for the footswitch like a 9V battery.