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Colorsound Power Boost - Another issue!!!

Andy Betts

Hi guys,

 

Been a long time since I posted here and i have another issue for you that hopefully you might be able to help with.

 

I've just recently built another Power boost pedal for a client. I etched the board myself using the photo resist method, it came out not too bad save for a couple of areas where the tracks were broke. i patched them up with copper tape that has conductive adhesive. I've checked for continuity and all is fine where the patches are. Here are the pictures of the board and also for reference the schematic.

 

 

image

 

image

 

I've built a few of these now and have had no issues with the circuit or builds until now. I built this one, wired it to my test rig and there is no sound at all.... it's totally dead as if it's not in the circuit at all. I've checked for voltage on input and it's ok. I've checked for continuity in the circuit and it seems ok. i don't know what the voltages should be in the various sections of the circuit so haven't checked them. I've gone basic and checked the input and output wires for breaks and they're ok. I've also checked the test rig with a known good circuit and it's OK.

 

i think there might be a duff component but not sure on first steps to troubleshoot.... Any help will be greatly received.

Parents

  • Hi Mike et al

     

    Voltages are as follows... I think Q3 is duff

     

    Q1 E = 5.83, C = 5.825, B = 5.83

    Q2 E = 5.15, C = 5.79, B = 5.79

    Q3 E = 0, C = 0, B = 0.58

  • in reply to Andy Betts

    Not necessarily:

    You have base emitter voltage on Q3 that looks about right - if the emitter resistor or cap was shorted the transistor would be turned hard on

    and the collector voltage would be low (although not quite zero).

    If Q3 was collector/emitter short there would be a voltage across the 1k emitter resistor.

     

    If your DMM is up to it try measuring the resistance Q3 emitter to ground - should be 1k but only if the DMM uses a low voltage.

     

    Otherwise remove the cap and see what happens to the Q3 voltages. (I reckon duff cap more likely than duff resistor).

     

    MK

Reply
  • in reply to Andy Betts

    Not necessarily:

    You have base emitter voltage on Q3 that looks about right - if the emitter resistor or cap was shorted the transistor would be turned hard on

    and the collector voltage would be low (although not quite zero).

    If Q3 was collector/emitter short there would be a voltage across the 1k emitter resistor.

     

    If your DMM is up to it try measuring the resistance Q3 emitter to ground - should be 1k but only if the DMM uses a low voltage.

     

    Otherwise remove the cap and see what happens to the Q3 voltages. (I reckon duff cap more likely than duff resistor).

     

    MK

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