Amp Channel indicator

[matt.dyck.music]

On the channel switcher pedal I built, the LED isn't working. I followed the exact same wiring scheme of the pedal the amp comes with (except without the boost switch). Anyway, the LED indicator works if I touch anything conductive between the resistor and LED. Example: if I touch my finger to any part of the wire connecting the two parts, or if I touch a guitar cable to it. Of anything noon conductive pushes on it, nothing happens, which leads me to believe that it's not just a bad solder joint. Any ideas? Thanks

[matt.dyck.music]

Hmmm... I tried connecting a 9 volt battery to the tip and sleeve of the jack and it lit up fine. So I now for sure the connections are all fine, but it still does the same thing.

[mth5044]

It would help to know what switcher you are talking about.

But, check to see that your amp is putting out voltage to power the LED. Does the original use a resistor/did you use the right value? If you turn the lights out, does it glow a little?

[matt.dyck.music]

I'm thinking it has to do with not having the second stomp attached, cause that's really the only difference in wiring. Anyway, it puts out 1.97 volts from the amp, I got a super bright LED and put a 4k7 resistor as I saw recommended for such a bright LED. The original pedal has a resistor (not sure what type) and a plain red LED.
My biggest confusion is this: if there isn't enough power from the amp, or the resistor is too high a value, then why is it bright enough when I add another conductive material but without adding voltage?

[matt.dyck.music]

Actually, let me make this simpler. The amp uses a trs for the footswitch which has two stomp switches. For the amp channel switch the tip gets connected to the sleeve, for boost the ring is connected to the sleeve. 1.97 volts runs through the circuit.
What I'm trying to do is make another switcher that only has the channel switch. So far the wiring for the switch works exactly how I want it, but the LED does not work. Does anyone have a wiring diagram of a simple footswitch that connects tip to sleeve and has an LED?

[slacker]

1.97 Volts might not be enough voltage to light the LED, some LEDs need more voltage than that, blue ones for example normally need at least 2.5 Volts.
If you've got a meter try powering the circuit with a battery and measure the voltage across the the two legs of the LED, if it measures more than 1.97 Volts in ain't going to work.

[matt.dyck.music]

Yeah, I just tested using my meter. I'm pretty sure it's just not enough power. That kind sucks.

[slacker]

You could try a much smaller resistor, the 4k7 recommendation was probably for running a LED off 9 Volts. Try something like 100 Ohm or measure the one in the original switch to get an idea.

[matt.dyck.music]

I just tried without even including a resistor, just connected the circuit to different batteries. It needs at least probably 2.5 volts and then only got bright enough by the time I had 4 volts. So yeah, I'm not sure what I can do now other than steal the LEDs from the other pedal.

[mth5044]

Get a not-super bright LED or a different color, or filter results in mouser to try and find one in the color you like with a lower on voltage, if it exists.

[matt.dyck.music]

Alright, thanks for all the input guys.

[mth5044]

Or put a 9V battery in the enclosure. That would last some time.

[MrStab]

it was before i knew a little better so i can't remember the ins & outs, but i once tried making an amp footswitch with LEDs powered by the control voltage (where there were none before) and the channel LEDs on the amp itself didn't like it. one always stayed dim instead of turning on completely. i MAY be imagining this, but i think it also put the amp into a weird half-switched mode, as that line was meant for switching and nothing else.

...so i'm gonna go with Matt's suggestion - you should use a separate battery.

also screw Marshall for whatever the hell kinda armour plating they use on their footswitch enclosures!!