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Blown Boss DD3 - help!

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  • Blown Boss DD3 - help!

    So a while back at a time when I was less wise on electronics I got my hands on a Boss DD3 delay pedal, and stupidly plugged it into an incorrect power supply (positive polarity I believe). I've just started the task of fixing this pedal but have run into some problems.

    First of all, I cannot seem to trace the +9V supply to anywhere on the board, it seems as if the line from the DC board to the main board (wire 2) is completely dead, so I'm wondering if maybe the transformer (at least thats what I think it is, it looks like an inductor joined with a capacitor on the schematic) on the DC board is bust. I can pick up 9V across the DC input socket and from wire 3 to one of the jacks, but not to the board itself. I'm really confused here unless theres some differences between this model and the schematic I've been referencing (

    I can clearly see that D6 on the board has blown and tried replacing it with a standard signal diode. Whilst this meant that the LED then turned on with the switch, there was no delay output (just a clean signal). I then realised that D6 is actually a zener diode, so have ordered an 11V replacement. I also believe that IC10 (5V reference) may be the problem as it is in close proximity to the diode and would be the reason for the lack of 5V reference voltage for IC7 and hence no delayed signal. Weirdly it now seems that I cannot actually trace any signal on the board after removing the incorrect diode, so am starting to think that the board is possibly gone beyond repair. Any pointers in the right direction would be greatly appreciated!

  • #2
    So, if I read this correctly, you have 9V or so into the 5v regulator, but no output? If so, try changing the regulator. It's also quite possible that Q1 FET was damaged when the wrong polarity power was applied. Trace the signal through Q1 and Q2 and make sure it is getting to the input of IC1.
    "Yeah, well, you know, that's just, like, your opinion, man."


    • #3
      Originally posted by welhamc View Post
      so am starting to think that the board is possibly gone beyond repair.
      Beyond repair???

      Not really, nothing is beyond repair.

      Relax, study the circuit more, and learn more.

      I've repaired quite a few DD2/DD3 pedals. All had the D6 burned, some of them had a hole in the pcb in the place D6 burned.

      There's a lot of info on the web on repairing these pedals, there's even a List somewhere of the most common problems and how to proceed in repair them.

      First of all,
      whats the model you have? long chip version?
      if a it's a newer unit whats the model?

      you have to post pictures of your pedal and the pcb, and of the parts you are talking about, otherwise it will be hard for someone to give you some guidance