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Please help an R/C brother

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First of all, let me say sorry if this is in the wrong spot (or forum) I didn't know where else to go...

I am an experienced rc pilot that has gained lots of advice from RC-Cam's site in the past.

I am also a musician who needs to mod some gear. I know it is an easy project, I just need some help.

On my amplifier, I can change channels between a clean sound and a distorted sound. The footswitch that controls the channels achieves this by "shorting" the tip to the sleeve of the cable that attaches the footswitch to the amp. There is a led that lights up when the connection is made. (thus changing the channel)

Sounds simple right?

Here's my challenge...

I want to add a second led that is lit when the other channel is operational. If the switch is open (no connection) there's no power to light a led.

There has to be a switch (double pole, double throw, triple, etc...) that will allow me to open the main connection and close another one -just for the other led.

If anyone can help me with this, I'd be really greatful.




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First, let's consider how the switching circuit is developed. I've never actually worked on amps with "effects packages"; pretty much limited to rebuilding old Fenders. In fact I recently finished a Bassman 75 for my much older brother; new rectifiers, caps, and a NOS set of Amperex tubes. But, very limited experience with the newer guys so, I'm gonna take a guess or two.

First, I'm guessing that the entire circuit runs: "Ground-> LED-> footswitch "ON"-> NPN switching transistor"; and that it feeds through a standard 1/4" phone jack and (hopefully) coaxial cable. In order to lighgt a second LED for the "off" position; you'd have to come up with a filtered DC source voltage to feed thus: "ground-> footswitch "OFF"-> 2nd LED-> source voltage" Needless to say, you're not only going to need to develop that "OFF" source voltage; but also you'll need the SPDT switch as well as a three-conductor 1/4" jack (Very easy - a stereo headphone jack!) and some three conductor audio cable, which could best be an "extension cable" for stereo headphones. Based on my assumptions above; the hardest part will be developing that "OFF" source voltage. First, measure the voltage fed out to the footswitch with the overdrive turned ON; then build up a suitable circuit (zener diode, etc) to match that voltage for the "OFF" LED.

Now, it's conceivable that your circuit uses a PNP switching trasnistor to turn the overdrive "ON"; in this case you have to reverse the polarity of the LED (swap its leads in the circuit. Otherwise, your project is all the same as above.


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