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oh dear, whammy, what did i do?

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  • #16
    yea. i think that would help me understand better too. i cant find a schematic anywhere.

    so is that -3.3 or +3.3?

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    • #17
      LD33V

      LD33V is a positive 3.3V regulator
      Power33LD33V \ Learning \ Wiring ALPHA 1.0

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      • #18
        The 3.3V is probably to run the big custom chip that does the whammying. An IC designed for 3.3V will not like having 9V shoved up it at all.

        Still, the troubleshooting approach is to get another LD33V and replace the one in there. If the pedal starts working again, great. If not, you've most likely blown the custom chip and turned your pedal into a doorstop: you can't buy a replacement as far as I know.

        There is a third possibility, maybe some little 5V rated bypass capacitor in there shorted out, and gave its life to save the IC. Or, maybe there are several ICs running off the 3.3V rail, and the one that blew is a non-custom part that you can replace.

        But according to Murphy's law, I'd suspect the main chip first.
        "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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        • #19
          yea. i am gonna just get the part and see if it works.
          very expensive lesson if not.
          oh well.

          i have looked all over for the diagram and its not to be found.

          from what i can make out of the tiny and confusing circuit board, the out from the regulator has 3 big caps to ground before it gets anywhere then the power splits to several places on the same chip. some via a surface mount cap or resistor, other points go direct in.

          just fingers crossed i guess
          thanks for your help guys

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          • #20
            New Part

            I would check the resistance (on the PCB with the bad IC removed) from the Middle leg, Vout, to the Left leg, Ground, before I put a new IC in.
            High resistance is good. Low resistance is bad.(relatively)
            No sense ruining it further.

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            • #21
              ok, i just did that.
              looks like it might be worse going on what you advised
              there is only a 2.2r resistance.

              i have taken a picture to try and make it a little clearer but i dont think i will ever get a schem for it. dont think it will be that much help tho my camera doesnt seem to do well with stuff that small.
              <br><p>

              http://i109.photobucket.com/albums/n76/kepeb/wham2.jpg

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              • #22
                3.3V buss

                You could try to trace out the 3.3V buss.
                At each connection to an IC, lightly cut the copper trace at that part.
                When the 2 ohm resistance bounces up to something realistic, you have found the toasted IC.(s)
                I see surface mount parts. If any are ASIC's(application specific IC) you will not be able to find them "off the shelf".
                Sounds like a doorstop.
                TIE (technician induced error) Ain't it fun.

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                • #23
                  well i dont think i'm confident i could cut the tiny traces or put them back accurately afterwards.

                  what is the possibility that it will work with the new regulator before i try cutting traces etc? before i took the dead ic out that 3.3v buss was only getting 0.5v.

                  you mentioned earlier about causing more damage by installing it.. how would that work?

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                  • #24
                    also. before i removed the ic, some things i'm not sure i was clear on earlier which may give more indications...

                    when i initially turned the pedal on the Led's flashed briefly, they're supposed to stay lit when the pedal 'boots' but they didnt do that anymore, they did still flash tho. is that a good or bad sign?

                    when i hooked it up i still got clean signal going through the pedal... i just wasnt able to adjust anything because the led selector section was off. is indicative in any way?

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                    • #25
                      Shorted 3.3V buss

                      I do not have the unit in front of me.
                      My experience tells me that the 3.3V buss, shorted to ground (2 ohms from ground) is not good. A new IC will pop.
                      Pack it in. It's dead.

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                      • #26
                        ah ok, cheers man. that makes sense

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                        • #27
                          ah ok, cheers man. that makes sense

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                          • #28
                            Hi Kepeb, answer it yourself:
                            Multimeter on 20VDC scale, black probe to chassis or known ground, red probe successively tests all 3 regulator pins . If any measurement is positive, it supplies +3.3V (or at least it tries to) ; if any voltage is negative , it supplies -3.3V.
                            Post what you measure.
                            Juan Manuel Fahey

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                            • #29
                              what?

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                              • #30
                                i'm not quite sure where your going with that. or what i'm answering? i thought i had the answer.

                                if i understand what your asking for...
                                the regulator is a positive 3.3v regulator which has +9v on the input +0.5 to +0.9 on the output.

                                the out is shorted to ground somewhere possibly through an ic which is powered from the +3.3v buss.

                                as i dont want to risk further damage or 'TIE's' i wont attempt the micro surgery required to locate the exact fault. i'll leave that to someone else.

                                i figured i am better off to just get another one.

                                unless you have other ideas? i would be interested.

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