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    FS-2 Pic and/or Schematic

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    Austin Forrest

    Posts : 2
    Join date : 2016-09-17

    FS-2 Pic and/or Schematic

    Post by Austin Forrest on Sat Sep 17, 2016 9:55 am

    Hi everyone. I'm wondering if someone with an FS-2 footswitch would mind opening it up and posting a closeup photo or two of the circuitry, and or a schematic. I'm trying to build one, but can't get it to function properly. Thanks, in advance!
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    bordonbert

    Posts : 815
    Join date : 2015-01-28
    Age : 97
    Location : Southern England

    Re: FS-2 Pic and/or Schematic

    Post by bordonbert on Sun Sep 18, 2016 4:31 pm

    Try here:  TM18 Footswitch operation

    Make sure to read the whole thread to get the correct info. Also look at the link I gave in Post 3. It might be interesting if you are electronically minded. Wink
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    Austin Forrest

    Posts : 2
    Join date : 2016-09-17

    Re: FS-2 Pic and/or Schematic

    Post by Austin Forrest on Mon Sep 19, 2016 11:06 am

    Hey bordenbert... thanks so much. I had actually read your thread before, and followed your schematic for the H&K design, but was still having problems. I could get the ring switch to change between "clean" and "crunch", but when I closed the tip switch it would just default back to clean, instead of engage "lead".

    It turns out that, for me anyway, the 1k resistors were too much... I removed them completely and now it works fine. I read on another forum that the voltage is already limited in order to protect the LEDs on the front panel, so that it should be fine for the ones in the footswitch. Hopefully that's the case... if not, perhaps I'll try with some lower value resistors. Thanks for all the help... cheers! :-)
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    bordonbert

    Posts : 815
    Join date : 2015-01-28
    Age : 97
    Location : Southern England

    Re: FS-2 Pic and/or Schematic

    Post by bordonbert on Tue Sep 20, 2016 5:33 am

    No, you'll be fine without the resistors at all. H&K do their stuff in a particular way. Effectively it's a current being detected not a voltage. And with the contact shorted to ground current flows and is detected inside the amplifier. There is a resistor inside the amp to limit this to a particular level. We are just using that limited current to double up and drive the LEDs. Too much resistance in series with the LED drops the current to the point where it isn't high enough to trigger the change. It took me a while to get to see that, (duuhhh!), as it isn't how it is normally done. That said it's a good way to approach it.

    All you need in the end are the switches and the LEDs. I can promise you, if you can build stuff up on a bit of veroboard, the ability to have the three Red, Yellow and Blue LEDs acting exactly as it does on the amp is great. I can give you the circuit I came up with if it helps. It's only a handful of resistors and a few general purpose transistors and diodes, no special components at all. If you aren't an experienced builder/bodger then just stick to what you have, a pair of "either/or and both" LEDs.

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    Re: FS-2 Pic and/or Schematic

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