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Thread: PS-100 and FC-3B footswitch info needed

  1. #1
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    Exclamation PS-100 and FC-3B footswitch info needed. STOP PRESS - The solution is here!

    Hi guys. I'm a complete newbie here, this is my first post. I have a PS-100 which is an amazing piece of thinking. I'm looking for a footswitch with which to control it. I know the manual says that any "standard footswitch" will do and I have a Line 6 double switch unit which can be made to control the Fryette perfectly. However...

    The PS-100 only has front panel LEDs to indicate which channel is selected and in a live situation this can be awkward, footswitch LEDs would be so much better. It actually has no indication at all as to the state of the Fx Loop. I want to add LEDs to the switching setup which should be a done deal.

    I'm an electronics design engineer so this should be a piece of cake - should! There are two basic ways of doing this. 1) LED in parallel with the switch so it lights up when the switch is open, (they usually have a current limit resistor in series with the LED in the footswitch though this may be internal to the PS-100). 2) LED in series with the switch with cathode towards switch and ground, this will lift the lower voltage threshold by about 1.5V-3.3V depending on the LED. The sensing circuitry thresholds are usually designed to cope with that.

    I set my footswitch up to the second series option and it works perfectly with my Marshall and H&K amps, both the channel and Fx Loops switch and their LEDs indicate as they should. But The PS-100 which behaves correctly with bare switches stubbornly refuses to do anything when the LEDs are in place. So there is something not quite so standard about the PS-100 switch sensing circuitry. Perhaps its threshold levels cannot cope with the LED forward voltage drop.

    One thing I did wonder is whether the sensing voltage polarity may be reversed. If the amp switches by grounding or leaving open a negative line voltage then the LED would be reverse biased when the switch was closed. Does anyone have any experience of how Fryette wires their own FC-3B footswitch?

    Incidentally that would be the easy option to solve this issue, (a 1000+ pound unit is NOT supplied with one - eh?). Try getting one on the right hand side of the water! Hen's teeth and unicorn droppings are easier to source.

    Thanks in advance for any info you can offer.
    Last edited by Bordonbert; 2 Weeks Ago at 11:27 AM.

  2. #2
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    Default The Question is answered!

    I have now looked into this with the live unit back at home and the answer is ridiculously simple. The PS-100 switches a NEGATIVE voltage on its control lines for Channel selection and Fx Loop switching. This means the LED must be fitted in reverse to the normal way round.

    Simply put it in series with the switch but with its cathode towards the socket tip or ring terminal and its anode to the switch, through it and on to the socket sleeve terminal. The Channel selection is connected to the tip and the Fx Loop to the ring, and they both share the sleeve ground connection of course.

    It wasn't rocket science and I don't understand the element of secrecy at all. It took 5seconds to spot where the problem was, I suspected that might be the case in the first place but didn't have the unit at hand to test. So there you go. It only takes any old PS2 footswitch type, just as Fryette advised. The thing to spot was the direction of the LED.

    (I've tried attaching a correctly size limited bitmap of the schematic for that but the Attachment Manager doesn't seem to like me. It just selects the file, briefly whirs around, then displays nothing in my list. Am I allowed to upload graphics at my newbie stage?)

  3. #3
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    Default

    thanks for following up! I'm sure somebody else will find this very very useful at some point

    I don't know if attachment upload is currently working, but you can always upload the picture to an image website like imgur.com and copy the link here

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