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Vintage Morley Power Wah Doesn't Always "Wah"

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  • Vintage Morley Power Wah Doesn't Always "Wah"

    I have a vintage Morley Power Wah. It is the big chrome unit with hardwired 2 prong plug, likely from the 1970s.

    Recently, the "wah" effect itself has become intermittent. Sometimes it works and sounds absotuely perfect, other times the "wah" effect is gone and in its place is almost like a "limited-throw/very limited effect volume pedal"-like functionality when rocking the treadle.

    I have a brand new bulb installed and it lights up and I can see it via the power lamp, which is illuminated.

    Where should I be looking inside on the circuitboard to troubleshoot this issue? One or more components which I need to replace? If so, which ones?

    I have replaced components on circuitboards before so I have good soldering skills, etc. I just don't know what is causing this problem inside this pedal.

    Thanks in advance.
    LL
    Last edited by louloomis; 02-25-2020, 05:29 AM. Reason: Left out detail

  • #2
    The bulb shines on a photcell, and the pedal works a shield to vary the light. Try cleaning the photocell.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      Originally posted by Enzo View Post
      The bulb shines on a photcell, and the pedal works a shield to vary the light. Try cleaning the photocell.
      Good idea. I see where the photocell is. Do I clean the photocell with De-Oxit or? What do you recommend?

      Thanks.
      LL

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      • #4
        Originally posted by louloomis View Post
        Good idea. I see where the photocell is. Do I clean the photocell with De-Oxit or? What do you recommend?

        Thanks.
        LL
        No De-Oxit , just gently wipe it off with a clean soft cloth.

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        • #5
          Do I clean the photocell with De-Oxit or? What do you recommend?
          No reason for DeoxIt, as its no metal or electrical contact. A little warm soapy water applied on a Q-Tip should do. Dry with a tissue. Or use isopropanol.
          Use DeoxIt on the jacks, though.

          But as your problem is intermittent, there might be something else.
          Last edited by Helmholtz; 02-25-2020, 04:52 PM.
          - Own Opinions Only -

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          • #6
            Originally posted by Helmholtz View Post
            No reason for DeoxIt, as its no metal or electrical contact. A little warm soapy water applied on a Q-Tip should do. Dry with a tissue. Or use isopropanol.
            Use DeoxIt on the jacks, though.

            But as your problem is intermittent, there might be something else.
            I just cleaned the photocell. It didn't fix the issue.

            I realize now that what I am hearing is actually a very, very weak "wah" effect, not a weak volume pedal effect as I originally described. I think I perceived the volume as changing simply because there was more treble in the "toe down" position on the treadle. It's actually a faint "wah" effect, but so faint that I really didn't hear it. However, the full "wah" effect is no longer intermittent, it appears to be gone, so I guess the issue is worse.

            Any ideas about what I should look at next in terms of a solution?

            One thing I noticed is that, in the "toe down" position on the treadle, the top of the photocell is pretty much even with the top of the "curtain". Is this correct? I assume it is because when the issue was intermittent, the "wah" effect sounded great and the position of the "curtain" was the same as it is now.

            Thanks.
            LL

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            • #7
              can you provide any pics ??? Have you double checked for loose components, bad solder joints ??

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              • #8
                Here is a sample of photos of the interior of the pedal. Hope this helps. I have not checked for loose components and bad solder joints yet.

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                • #9
                  thanks for the pics , but these are generic pics not the actual pics of your device ?? actual pics might be of more help.

                  do you have a multi-meter?? If yes ,
                  Turn the multimeter on, and place it on the setting for resistance. If the multimeter is not auto-ranging, change the knob to a very high level, such as megaohms.
                  Place the red probe of the multimeter on one leg of the photocell, and the black probe on the other. The direction does not matter. You may need to use alligator clips to make sure that the probes do not slip from the photocell’s leads.
                  Shield the photocell so that no light falls on it. Do this by placing your hand over it or by covering it, for example. The resistance should be very high. Uncover the photocell and shine a bright light on the photocell the resistance should drop. That should at least tell you if the photocell is functioning. If you can do this, please write down your ohms readings.
                  Last edited by shortcircuit; 02-25-2020, 09:42 PM.

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                  • #10
                    No, these are not generic pictures. They are pictures I just took of the pedal I actually own so that I could upload them to this thread.

                    Yes, I have a multimeter and I also have alligator clips. I just did the test you requested. Here are the results:
                    1. With my light off and my hand almost entirely covering the photocell, the multimeter read like 1.5M ohms (if I shielded the photocell entirely with my hand it went to "0F".
                    2. With my light on the photocell, the multimeter read 257 ohms (not M or K).

                    I assume this means that my photocell works, true?

                    Thanks again.
                    LL

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                    • #11
                      My best guess is that one or more of the small yellow electrolytic caps is bad.

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                      • #12
                        My vote would be that some/all of those electrolytic caps are well past their prime.

                        How "vintage" is it? Any idea what year it was made?
                        The world is full of people that are right.

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                        • #13
                          OK great on the pics, my apologies . Yes I'd say P-cell is good, those readings seem about right. No insult intended the bulb is good correct ?? I would plug it all in, get someone to run the treadle and strum while you poke around with a chopstick, see if you get any results , again checking for loose connections. Can you get the exact model of pedal ?? a schematic ?

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                          • #14
                            dmeek - Ok. I only see 1 yellow disc capacitor. Did you mean that or the whitish cylindrical capacitors standing upright at angle?

                            galaxiex - Ok. The capactors are bad you think. In terms of its vintage, it is "Morley" but has the "Tel-Ray" name and address also on the metal Morley nameplate. Maybe it's late 1970s or very early 1980s?

                            shortcircuit - Thanks. NP at all about the pics. No impoliteness was intended in my wording, sorry if it came off that way. Thank you for your input. Ok, photocell is good. Yes, the bulb is good - just purchased it and it shines brightly. No insult taken, of course. Always good to ask. I think the exact model is "PWO". I plan to do the chopstik test, but I haven't gotten around to it yet.

                            Thanks.
                            LL

                            Comment


                            • #15
                              Originally posted by louloomis View Post
                              dmeek - Ok. I only see 1 yellow disc capacitor. Did you mean that or the whitish cylindrical capacitors standing upright at angle?

                              galaxiex - Ok. The capactors are bad you think. In terms of its vintage, it is "Morley" but has the "Tel-Ray" name and address also on the metal Morley nameplate. Maybe it's late 1970s or very early 1980s?

                              shortcircuit - Thanks. NP at all about the pics. No impoliteness was intended in my wording, sorry if it came off that way. Thank you for your input. Ok, photocell is good. Yes, the bulb is good - just purchased it and it shines brightly. No insult taken, of course. Always good to ask. I think the exact model is "PWO". I plan to do the chopstik test, but I haven't gotten around to it yet.

                              Thanks.
                              LL
                              At that age, late 70's early 80's, I would wholesale replace all electro's and trouble shoot from there.

                              My guess is those small CSA electro caps are the most likely culprit.
                              The world is full of people that are right.

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