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Thomas Organ cry-baby like a volume pedal

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  • Thomas Organ cry-baby like a volume pedal

    I found my old '70s Thomas Organ cry baby, tested it out and found that it was acting like a muffled volume pedal.
    Then did the following:
    - setup true-bypass
    - replaced all capacitors
    - replaced some resistors per tone recommendations..
    - replaced jacks
    - replaced pot
    That's all I can think of.. Result: same muffled volume pedal, except tone is thicker and louder.
    I understand that if there is no "wahh", then the electrolytic cap negative may not be connected to ground.. but .. it is, measured w/ ohm meter.
    The inductor seems OK - was measured as well... and had some resistance - didn't note the value.
    The layout is like this, http://fulltone.com/ThomasCrybaby.jpg except the 3.9uF cap is now 4.7uF, and some resistors values changed.
    I also measured resistance on the old cables.. All seems OK..
    Overall the result is pretty much the same as when I started though.
    I have the original parts if I want to go backwards to the original caps..
    Any ideas? tips on what to test next?
    Thanks in advance

  • #2
    Originally posted by pbiagi View Post
    The inductor seems OK - was measured as well... and had some resistance - didn't note the value.
    Did you measure in or out of circuit?

    Regardless of the type of choke, a dc resistance reading should be less than 1K.

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    • #3
      Stands to reason that if you changed everything out except the inductor, it's probably the inductor.

      Comment


      • #4
        Well... what if I want to keep the stack of dimes "03" inductor and live in denial?.. I pulled it from the circuit and ... it's dead. (Thanks for making me face reality.)
        Now.. a long time ago I had a pickup go bad on a vintage guitar and I was able to find the tiny wire and resolder and voila the thing worked again, and still does. Any chance I could pull that off on this inductor?
        Or is it worth sending to an expert to get fixed?
        What are other choices for a good inductor?
        The whipple? Where to buy? ebay?
        I'd like a warmer sound, clean bass.. My memory is this 70's crybaby was a little harsh on the high end. Maybe the wipple is better than the stack of dimes.?

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        • #5
          I've used a few Whipples in some of the wahs I've built. It's a nice inductor.
          Ebay seems to be the place to get them. Here's a thought! Try contacting the Whipple guy and see what he thinks about rewinding/repairing the inductor for you. Might be worth a shot.The cost of fixing it might just be too much though. Couldn't hurt to ask though.

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          • #6
            Cry Baby

            jusdt get a whip.it will sound good you can not sound like the 1970s C-B you changed all the values

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            • #7
              Ok, installed the whipple .. and it still operates as a volume pedal..
              I measured the whipple before installing it and had 10 ohms resistance.

              All the resistors were not changed, just some.
              The two transistors were not changed either.
              I've checked the wiring continuity and all seems good..

              I'm going to try changing out the two transistors..
              Any other ideas?

              Thanks in advance

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              • #8
                Wait! Now you are saying you didn't change everything out?
                Take another look at your 4.7uf cap. Make sure it's got the negative to ground and that it's not bad. That will make you have a volume pedal. Other than that, there shouldn't be too many more parts for you to swap out so I would just go all the way and finish swapping everything out. If it still doesn't work after that, you have a bad part or you have the wrong component value somewhere.

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                • #9
                  Hi BB,

                  Yes, I already switched out the 3.9uF cap with a 4.7uF electrolytic, and the polarity is good.. I was convinced that was the issue..
                  Question: does it make a difference what voltage the other caps are?
                  Currently the two 0.01uF are 600V, and the two 0.22uF 250 V.
                  (Big, but couldn't find smaller voltages handy.)

                  The new transistors have inverted c-b pins compared to the existing..

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                  • #10
                    Oh, and the 4.7uF cap negative to ground has continuity..
                    (I figure I'm learning a lot on this.)

                    Comment


                    • #11
                      No, voltage doesn't make a difference unless the voltage is too low for the voltage of the pedal. You are well above that!
                      Yes, make sure the pin configuration is right when you insert them. Using sockets for the transistors is a good idea.
                      Also, double check you have the right resistance values for the resistors. If you post pictures, I'll take a look.

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                      • #12
                        Replacing the transistors didn't help.

                        Sorry, the pictures aren't great - taken from phone which is all I have handy.

                        The diagram may be helpful. I did a number of popular mods, including true-bypass. My thinking was by doing the mods, I'd probably fix the problem.
                        The switch, jacks and pot are replaced. Pot is a 350K (or something like that). I think the original is 100K, haven't measured.
                        Everything outlined in blue has been replaced, and blue values are those different from original values, which are indicated in black to the side.
                        The values are changed per mod recommendations. I measured resistor values before installing.
                        The wiring is kind of old and brittle. One to the post simply broke off. However continuity is testing out. Maybe I should re-solder them all to the posts.

                        Let me know if you want better photos and I'll try to post tomorrow.
                        Attached Files

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                        • #13
                          Oh and don't laugh about the giant 0.22 caps and how they are hooked up!
                          ... well ok.. you can laugh, I can take it.

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                          • #14
                            It's too hard to tell with those pictures. They are just too blurry. I was going to make sure all the resistors were the correct values and in the right places but I just can't tell. Are you sure you connected the right pins of the Whipple? I'm going on vacation in the morning until the 12th so I won't be able to take a look at any pictures until I get back.

                            Comment


                            • #15
                              I feel bad for you.You will have to start over and track what you did.Maybe that Pot is too high.Its just one thing, but finding it is the problem, Go to DIYstompbox.com

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