Home › Forums › Vintage EHX › 1970’s MUFF FUZZ TRANSISTORS

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  • January 26, 2020 at 9:49 pm #86119
    Paulh
    Participant

    Hello:
    I am back, last post was around 9/14/16.
    Topic is my 1978 Muff Fuzz lost it’s Fuzz. After a long delay I started on this project again.
    I am writing this to let you know how I solved the problem.
    Using a bread board I duplicated General Guitar Gadgets schematic using 5088 and 914.
    Did not work (only had gain) UNTIL I replaced the 10K resistor with a 68K resistor. Then it sounded great!
    So I did the same with the Muff Fuzz unit which has a similar circuit (polarity is reversed) and some connections are different, plus BC239 and 239c are original.
    And IT is finally FUZZING once again.
    Now it has all the 1978 original components except for that 68K resistor.
    Switch and pot work great.
    Thanks again for your help (a few years ago).
    Regards
    Paul

    January 31, 2020 at 4:43 pm #125788
    Paulh
    Participant

    Paul here again:
    Well looking for clues on Muff Fuzz circuits I noticed that what I thought was a 27K resistor on paper is actually a 2point7K resistor (2K7). In the original 1978 Muff Fuzz enclosure resides a 27K resistor and that 10K resistor (that I changed). Yup Red Purple ORANGE (and I measured it out of circuit). So I am wondering if a mistake was made during the original assembly way back in 1978. Should be Red Purple RED. Went back to the breadboard and changed out the 27K and 68K (fix) with a 2K7 and 10K……..FUZZ (instead of just some gain which was the original problem).
    Mystery solved. Anyway the original Muff Fuzzes with that 27K and 68K (fix) so I am happy.
    It is still positive ground with BC239 transistors and sounds good. Just can’t plug it into another neg grnd box.
    Regards
    Paul

    February 3, 2020 at 8:54 pm #125792
    j_flanders
    Participant

    Are any of the online schematics correct when compared to your Muff Fuzz (apart from the resistor mistake)?
    If so could you please post a link.

    I love my Double Muff btw but the circuit is slightly different from being just two Muff Fuzzes cascaded as it is being advertised. Well, at least if I go by the Muff Fuzz schematics I find online.

    February 3, 2020 at 10:34 pm #125793
    Paulh
    Participant

    General Guitar Gadgets website has the transistor version schematic. It does not show a dpdt switch. But the circuit is much the same as my small box muff fuzz EXCEPT for the polarity. Npn transistors are BC239. I would not duplicate it because of the positive ground unless if that is what you want. I have not found the circuit of my muff fuzz on the web, but I have drawn it.

    February 3, 2020 at 10:53 pm #125794
    j_flanders
    Participant
    Quote:
    I have not found the circuit of my muff fuzz on the web, but I have drawn it.

    I’d love to see (and build) it. If you cannot post schematics here maybe you can send it in a private message?

    February 4, 2020 at 3:30 pm #125795
    Paulh
    Participant

    Here is the circuit for my 1978 (when I bought it) Muff Fuzz.
    I changed the 10K resistor to 68K to make it work.
    It has a Positive ground so, I guess you are not supposed to use it at the same time with other Negative ground devices.
    The elec cap is 33uf and I have seen 47 and 50 used….whats the difference???
    Also try 2N3904 and 2N4401, they make a different sound.
    Have fun, make sure all grounds are made….
    The voltages are way different plus depends on the actual v of the battery during the test:

    Nearest amp
    E 8.25
    B 7.69
    C 2.99

    Other
    E 9.39
    B 8.83
    C 7.69

    February 4, 2020 at 4:30 pm #125796
    j_flanders
    Participant

    Thanks a lot for the schematic!
    Any idea what the original diodes were? (silicon or germanium?)

    Quote:
    It has a Positive ground so, I guess you are not supposed to use it at the same time with other Negative ground devices.

    You can use it together with negative ground devices but you cannot daisychain them from the same power supply. It needs its own, battery or adapter.

    Apart from the transistors, and diodes perhaps, most schematics online look to be accurate.

    It’s a silicon Fuzz Face variant btw (but it has no bypass cap on the emitter of Q2 and therefor a lot less gain, but it has (clipping?) diodes on the output.

    February 4, 2020 at 4:50 pm #125797
    Paulh
    Participant

    The diodes in that old Muff Fuzz are very small like 1N914, so I guess they are germanium.
    The circuit in that little box was made very tight, the diodes were soldered with the leads “nonexistent”.
    Surprised they did not fail.

    February 4, 2020 at 5:15 pm #125798
    j_flanders
    Participant
    Quote:
    The diodes in that old Muff Fuzz are very small like 1N914, so I guess they are germanium.
    The circuit in that little box was made very tight, the diodes were soldered with the leads “nonexistent”.
    Surprised they did not fail.

    Hehe ok.
    Yeah on most photos I find online they look like 1N4148 or 1N914 but just wanted to check with yours.
    1N914 is silicon though, but that’s ok.

    February 4, 2020 at 8:04 pm #125799
    Paulh
    Participant

    Yes like I said 1N914 is silicon ! Bought them on Prime, free shipping…RS is long gone, like who is next.
    Got the positive ground version on a bread board and have tried 1N34A Germanium without much change, I like the 914’s.
    Also just tried to put a 100pf cap between base and collector on Q2. No results.
    How about the ele cap, what might that change ?
    Thanks for the thread..
    Paul

    February 4, 2020 at 9:32 pm #125800
    j_flanders
    Participant
    Quote:
    Also just tried to put a 100pf cap between base and collector on Q2. No results.
    How about the ele cap, what might that change ?
    Paul

    A small cap between collector and base reduces gain for (very) high frequencies. In general it will prevent fizzy top end distortion. But if the cap is (too) small or the gain rather low the effect is very subtle or inaudible.
    Sometimes people use it to simulate germanium transistors when using silicon transistors. Germanium transistors have this extra capacitance internally. You can replicate it on silicons by adding it externally.

    Normally that big electro cap across the power rails is used for power filtering (removing ripple) but in battery operated pedals there’s no ripple to remove, so I guess the only reasonable explanation is this one by PRR:
    https://www.diystompboxes.com/smfforum/index.php?topic=113734.msg1053703#msg1053703
    and this one by Teemuk:
    https://www.diystompboxes.com/smfforum/index.php?topic=113734.msg1054057#msg1054057

    February 6, 2020 at 8:24 pm #125804
    Paulh
    Participant

    Well here it is.
    The Fish Fuzz.
    Has an IC socket to change to different transistors (I have 4).
    The box cost 3 clams at an antique shop down the road.
    My laser cut and etched on this project.

    February 6, 2020 at 11:31 pm #125805
    j_flanders
    Participant

    I think it looks great but can’t tell for sure as the pictures are so tiny (about an inch wide) :)
    The thumbnails are even bigger than the image when clicked.

    Edit: I see there’s a limit of 75kb per attachment. Seems like a limit from 1975. :)
    The smileys are from that era as well. lol

    February 7, 2020 at 3:38 pm #125807
    Paulh
    Participant

    Bigger pics.

    February 7, 2020 at 3:39 pm #125808
    Paulh
    Participant

    Next.

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