How do you wire LED's with momentary switches?

Ah, so the amp does have LED indicators. If only there was a way of connecting to those the sync problem would be solved!.....
You mention 'if the footswitch does not have LED's', suggesting there are some commercial footswitches which do have LEDs. If that's the case I wonder how they overcome the sync problem?

Here is a link to a schematic for a Marshall amp that I have been able to put together a footswitch for without LED's, but I need to add LED's to it. I do not have the skills to decipher the schematic, but it seems like you do. Maybe you can tell how they get around sync issues by the schematic. The footswitch portion appears to be in the upper left hand side of the 5th page of the schematic.

Here's the link:

https://www.drtube.com/schematics/marshall/jmp1-61-04.pdf

alec_t said:

Ah, so the amp does have LED indicators. If only there was a way of connecting to those the sync problem would be solved!.....
You mention 'if the footswitch does not have LED's', suggesting there are some commercial footswitches which do have LEDs. If that's the case I wonder how they overcome the sync problem?

Click to expand...

Yes, page 5 covers the footswitch input. The switch presses are monitored by a microprocessor, which selects channels accordingly and also controls the digital display and button illumination. I think connector CN3 carries channel-select signals, but I doubt that would be readily accessible for tapping off sync signals for footswitch LEDs. Major dismantling of the amp would probably be necessary, with no certainty of intercepting the correct signals.

alec_t said:

I've redrawn the circuit to clarify things (I hope!).
View attachment 56221
The switches SW1-SW3 are now shown in a more conventional way.
The latches are identified as type CD4013.
The D input of each latch is connected directly to 0V (represented by the triangle symbol).
R9 is the pull-down resistor which I mentioned in post #21 (the 4 resistors you added to the schematic were not connected to 0V as I suggested, and only one pull-down is necessary anyway).
R2-R6 are shown as 1k (which is perfectly suitable for 9V use, as you have already found).

Edit: All references to 5V on the schematic should be corrected to 9V. The NC contacts of the switches are unused, and the centre tabs connect to V+.

Let us know how you get on.

Click to expand...

Hi,
this is my first intervention on this forum, and I would like to congratulate to all of you for the great work done!
I'm setting a PCB for the schematich drawned by alec_t but I'm not sure about connections of CD4013.
This chip have 2 operational amplifiers inside, so I can use 1 chip for 2 switches, is it correct?
Then I've found at the "Holy" datasheet.com the pins configuration of the CD4013 that I've bought:
View attachment 65220
wich is the correspondence of the pins? I understand that:
PRE=set pin, D=data input, CLK=clock input.
But I don't have correspondence for the others pins, can you help me to connect the others pins?
Then I've one more question, where I have to connect the Vdd and Vss pins of CD4013?
Vdd to +9V and Vss to ground?
Thank you so much!
P.s. Sorry for my English ...

This chip have 2 operational amplifiers inside, so I can use 1 chip for 2 switches, is it correct?

Click to expand...

Yes. The two latches in the CD4013 can be used independently.
Pinout:
1= out 1, 2= not-out 1, 3= clock 1, 4= clear (reset) 1, 5= data 1, 6= preset (set) 1, 7= Vss (ground).
8= preset (set) 2, 9= data 2, 10= clear (reset) 2, 11= clock 2, 12= not-out 2, 13= out 2, 14= Vdd (+9V)

alec_t said:

Yes. The two latches in the CD4013 can be used independently.
Pinout:
1= out 1, 2= not-out 1, 3= clock 1, 4= clear (reset) 1, 5= data 1, 6= preset (set) 1, 7= Vss (ground).
8= preset (set) 2, 9= data 2, 10= clear (reset) 2, 11= clock 2, 12= not-out 2, 13= out 2, 14= Vdd (+9V)

Click to expand...

Thank you very much you've been really a great help for me!
I will post how I get it on