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marshall tsl60 switching problems

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  • #1

    marshall tsl60 switching problems

    Hi
    I dont have a tech I can go to for miles so hopefully someone can point me in the right direction
    I have a tsl60 and it wont switch between od1 and od2. When switching between clean and the od channels it will go to od1 and then wont change to od2 with either the front panel switch or the footswitch. The red LED doesnt light up at any time and the relay doesnt click.
    Im assuming something in the switching circuit has failed but I dont really know where to start with the circuit. I can test the relay coil and contacts to make sure its actually working but other than that Im a bit stuck. Im capable of using a multimeter etc.
    Any help?

    Thanks
    Tags: None
  • #2
    TSL footswitch switching problems

    I had a similar problem with my TSL 100 footswitch. I debugged it to be a bad transistor on the footswitch circuit board. Also had a bad switch that I replaced.

    I actually created a full schematic to figure out what was going on if you want ht, I can email.

    Also - I am not trying to replace a bad cable and having trouble finding parts. I f someone can help on that, great!

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    • #3
      Ive tested the relay out and thats working fine. I also noted that the lead gain and volume controls also arent switching in so the fault is before the relay coil in the schematic. Any ideas?

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      • #4
        Check the foot switch...

        If the LED's on the switch aren't correct, the problem has to be in the footswitch
        If you open in up, you should probe pins 4 and 5 coming off the cable.
        Here's the map
        Pin 1 - Ground
        Pin 2 - Can't remember whether this is for Reverb or Effects Loop
        Pin 3 - Can't remember whether this is for Reverb or Effects Loop
        Pin 4 - If Logic 0 (<1 v), Crunch Should be Active, if Logic 1 (>5V) Lead should be active
        Pin 5 - If Logic 0 (<1 v), Clean Should be Active, if Logic 1 (>5V) check pin 4
        Pin 6 - Power - should be around 20 volts

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        • #5
          Thats useful for knowing what the pins do but its not the footswitch alone causing it as I cant switch to OD2 regardless of if Im using the footswitch or the front panel buttons.
          Ill check how far thew switching goes before it stops working. It must be T5 or before as the relay isnt switching on

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          • #6
            Oh - yeah than you probably have to keep tracing back inside the amp.

            Is the footswitch completely unplugged?

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            • #7
              I'd be looking for a bad little transistor in the switching circuit inside the amp. Without me looking it up, if there is a 2N7000 in yours, it is the first suspect.
              Education is what you're left with after you have forgotten what you have learned.

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              • #8
                Ive done a bit more investigation on this now. AS far as I can tell all the transistors are working (there are no 2n7000s present) but there seems to be a lack of base current to actually make them switch. Ive had a look at the joints and the traces and as far as I can tell they are ok. Im thinking the front plate switch may be shorting to ground all the time as that would explain its problem
                any thoughts?

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                • #9
                  Originally posted by whalenlg View Post
                  Oh - yeah than you probably have to keep tracing back inside the amp.

                  Is the footswitch completely unplugged?
                  the operation is identical with the footswitch plugged in or plugged out

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