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Boss Metal Zone MT-2 Help Needed to fix.

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  • Boss Metal Zone MT-2 Help Needed to fix.

    Hi, wonder if someone can help me with this pedal that is not working correctly.
    When hooked up between the guitar and amp, with no other pedals between; with the battery (New) or a 9vdc (Tip negative) 300ma power supply. In bypass sounds pass right through to clean channel on amp. Step on pedal, red led lights, same sound comes through on amp. Now the strange thing is, when the level control is at 12 o'clock sound is at the correct level. If I turn from 12 down towards 9 o'clock the level drops lower. This also happens when I turn the level up from 12 towards 3 o'clock. Odd eh?
    There is absolutely no distortion or any tone difference when any of the eq knobs are turned or the Distortion knob.

    I've opened up the pedal and everything looks and smells brand new. No solder bridges, burn marks, overheated IC's or Transistors or Fet's.

    I have the schematic for it and have checked all the components to it, and maybe someone can help here; is the following right?
    All 4 Fet's seem correct (1 - 2sk184 at Q11 and 3 - 2sk118 at Q2,Q3,Q9)
    I have 5 - Transistors 2sc3378 (As shown on schematic, Q1,Q4,Q7,Q8, Q10)
    But the other 2 are 2sc2458 (Schematic shows other transistors as 2sc945 for Q5, Q6)
    The IC's I have are NJM 14558L for IC's 1, 2, and 4.
    IC 3 is NJM 4558LD Is this correct? or did Boss put the wrong IC into posistion 3?

    The unit looks and smells brand new with no signs of use or abuse. It came from a music store that was going out of business, so I have no history on it. Maybe it never ever worked. I'd sure like to fix it if I can. I can solder and have built my own pedals and amps etc before.
    Any help would be greatly appreciated by this old rocker.
    Thanks .
    John (61 year young, disabled Rocker)
    John (61 year young disabled Rocker)

  • #2
    Update

    Well, not having heard from anyone, I went ahead assuming all the components were correct.
    I checked the power supply and found that the pedal has the full +DC but the 1/2 +DC is only 1.25VDC.
    Now I just have to find the component(s) that are dropping the voltage down.

    Anyone ever experienced this before?
    Any advise as to what may be wrong?

    Regards
    John (61 year young disabled Rocker)
    John (61 year young disabled Rocker)

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    • #3
      Finally Finished

      Well after having to put this project on the back burner while I got certain things done around the house. I am pleased to say that I came back to it yesterday and was able to get it up and running.
      The problem with the voltage being low was due to the opamps being no good. I had signal getting through to IC 3pin 5 but nothing coming out pin 7.
      So I removed each IC and tested the voltage and nothing changed until all IC's were removed. So I think this poor pedal got and adaptor plugged into it that either had the wrong voltage or wrong polarity voltage. I replaced all the IC's with M4218AL's and its running great.
      So I hope this may help someone out if they have the same problem.
      Well, got to go and make some noise!
      Cheers!
      John (61 year young disabled Rocker)

      Comment


      • #4
        John, if you have more questions about Boss pedals you might visit the Bossarea forum, there's lot of info to find there.

        http://www.bossarea.com/forum/

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        • #5
          Thanks for the information

          Thank you for the information and the link Mesjoggah.
          John (61 year young disabled Rocker)

          Comment


          • #6
            Originally posted by JohnR242 View Post
            Well after having to put this project on the back burner while I got certain things done around the house. I am pleased to say that I came back to it yesterday and was able to get it up and running.
            The problem with the voltage being low was due to the opamps being no good. I had signal getting through to IC 3pin 5 but nothing coming out pin 7.
            So I removed each IC and tested the voltage and nothing changed until all IC's were removed. So I think this poor pedal got and adaptor plugged into it that either had the wrong voltage or wrong polarity voltage. I replaced all the IC's with M4218AL's and its running great.
            So I hope this may help someone out if they have the same problem.
            Well, got to go and make some noise!
            Cheers!
            This is confirmed working. After measuring the voltage drop on ICs 1-4 and no to avail. I did the same thing as John. 100 % working. Kudos mate!

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