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Thread: Tube screamer TS808 failing

  1. #1
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    Tube screamer TS808 failing

    TS808 failing ,,Replaced with new original stomp button ,,, also tried Standard momentary ,,Pedal will work 30 times with no problems ,,then when stomped it will fail no sound ..Will stomp again and will work ,,all solder joints have been re-soldered and power connections have been checked ,,In and output jacks are good ,, Thinking transistors or Ic are having problems ? This is an Intermittent problem

  2. #2
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    Welcome to the forum.

    These pedals are sensitive to switch type. The circuit has a couple of components to 'debounce' the switching noise, but this only works well if the switch has a sharp transition to on/off. If the switch is of an incorrect type it will not switch cleanly and can occasionally flip the pedal to a random state and not appear to switch and you need to stomp again to switch the pedal You say you fitted an original stomp button - was this directly from Roland (Boss)? or a part bought off Ebay claiming to be original? So, the starting point is to make sure the switch is original, otherwise you can have two problems together.

    The actual switching flip-flop is a pair of transistors and does not involve the IC.

    You say your pedal is completely dead when it fails - is there any background sound at all?

    I find the best way to troubleshoot these pedals is to use an 'audio probe' along with the schematic. You need to establish how far the signal is getting - it may not be a switching problem at all as there are quite a few points where a component failure could result in signal loss.
    Last edited by Mick Bailey; 08-14-2017 at 05:36 PM. Reason: clarification

  3. #3
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    Quote Originally Posted by Mick Bailey View Post
    Welcome to the forum.

    These pedals are sensitive to switch type. The circuit has a couple of components to 'debounce' the switching noise, but this only works well if the switch has a sharp transition to on/off. If the switch is of an incorrect type it will not switch cleanly and can occasionally flip the pedal to a random state and not appear to switch and you need to stomp again to switch the pedal You say you fitted an original stomp button - was this directly from Roland (Boss)? or a part bought off Ebay claiming to be original? So, the starting point is to make sure the switch is original, otherwise you can have two problems together.

    The actual switching flip-flop is a pair of transistors and does not involve the IC.

    You say your pedal is completely dead when it fails - is there any background sound at all?

    I find the best way to troubleshoot these pedals is to use an 'audio probe' along with the schematic. You need to establish how far the signal is getting - it may not be a switching problem at all as there are quite a few points where a component failure could result in signal loss.
    Thanks for your reply . I am repairing this for the guitar player in one of the bands i run sound for , I did get the switch from mike ~^v^~ aNaLoG.MaN ~^v^~ guitar effects ,No matter what switch was used it did the same just quit and no sound . I asked analog man through emails and it went no where quick. I asked about the flip flop circuit got no answer so here I am .The switch is from Analog so Im hoping it's original

  4. #4
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    If you haven't got one already, I recommend putting together an audio probe. Just a regular 1/4" plug on a length of screened cable. Strip back the other end and attach a small non-polarized cap to the centre conductor. 0.22uf or 0.1uf or whatever - doesn't matter too much. The screen goes to a short length of wire to a crocodile clip. You can do this as fancy as you like and a quick search will give you some pics. Then you can set the pedal up with a signal going into the guitar input and use your audio probe through an amp to listen at various points in the pedal.

    Let us know if you've got set up with this and we can guide you through the process.

    Edit; Schematic here;

    ts808.jpg
    Last edited by Mick Bailey; 08-15-2017 at 09:21 AM.

  5. #5
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    Quote Originally Posted by Mick Bailey View Post
    If you haven't got one already, I recommend putting together an audio probe. Just a regular 1/4" plug on a length of screened cable. Strip back the other end and attach a small non-polarized cap to the centre conductor. 0.22uf or 0.1uf or whatever - doesn't matter too much. The screen goes to a short length of wire to a crocodile clip. You can do this as fancy as you like and a quick search will give you some pics. Then you can set the pedal up with a signal going into the guitar input and use your audio probe through an amp to listen at various points in the pedal.

    Let us know if you've got set up with this and we can guide you through the process.

    Edit; Schematic here;

    Click image for larger version. 

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    Thank you for the great reply ,Ill put a probe together today and test , Now hopefully I can get it to fail I am thinking if it is the flip flop circuit this will be a pain it the butt to find Hoping not I will let you know asap what i find

  6. #6
    Senior Member Enzo's Avatar
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    It quit with no sound, but you are suspecting the flipflop.

    Does the red light go on and off when you stomp the switch? If so the flip flop is flipping.
    Education is what you're left with after you have forgotten what you have learned.

  7. #7
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    Just thinking - does the LED turn on/off when the fault occurs, or does it stick?

    Edit; Enzo beat me to it!

  8. #8
    Old Timer J M Fahey's Avatar
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    Quote Originally Posted by kendrums1 View Post
    TS808 failing ,,Replaced with new original stomp button ,,, also tried Standard momentary ,,Pedal will work 30 times with no problems ,,then when stomped it will fail no sound ..Will stomp again and will work ,
    What does this exactly mean?

    1) you lose *all* sound, you get silence, neither clean nor distorted sound, even after repeated stomping?

    2) you have 2 sounds available, clean and distorted, you lose *one* of them, clean OR distorted.
    So stomping gives you either
    a) clean - click - silence - click - clean OR
    b distorted - ckick - silence - click - distorted

    As a side note: does the LED switch ON-OFF?

    Please answer which one applies.
    Juan Manuel Fahey

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