Heat and germanium transistors

Discussion in 'Effects, Pedals, Strings & Things' started by zygoat, Jun 7, 2008.

  1. zygoat

    zygoat Supporting Member

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    Last week I got a Proanalog MKIII in the mail, and I absolutely love the way it sounds. I remember a few threads about germanium transistors and the way temperature affects them, I tried a search but didn't get an answer to this question.

    I live in Florida and it's hot. Miserably hot. Mailman delivered the pedal to my door and I plug it in about 5 minutes later. The pedal itself is hot to the touch. Anyway, it turned on and off OK but when I adjusted the gain knob while it was on, it cut in and out. I took the pedal an inch or two off of the floor and tapped it back down to the floor and it came back on.

    After being in the air conditioning for 30 minutes it worked fine, and I haven't had any issues since then.

    Normal?
     
  2. gururyan

    gururyan Member

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    I haven't had that issue before (cutting in and out), and I live in a very hot and humid climate (tulsa, ok). Getting a bias added to my London helped though. Go toss it in the fridge and cool it down, you'll feel/hear a difference.
     
  3. ZMC

    ZMC Member

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    I have had the same expierience with my fuzz face and I think it is fairly common when the transistors get pretty warm. But I may wrong.
     
  4. analogmike

    analogmike Gold Supporting Member

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    I think you have a bad solder joint there, high or low temps will make it sound bad but still work ok.
     
  5. amz-fx

    amz-fx Supporting Member

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  6. fatback

    fatback Member

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    wow, those results were pretty substantial. thanks Jack.
     
  7. e-flat

    e-flat Supporting Member

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    While testing batches of transistors, I'm always amazed to see the Hfe rise and then drop after just a moment of handling.... I try to pick them up by the leads now : )
    Also, after making any mods to a pedal I always let it go through the "cool down" period (though i use heat sinks on trannie leads) so that I don't get a false (negative) impression of a steamy circuit : )

    Jack- I rmemeber seeing an article that you had posted about building a simple device to test leakage but I can't seem to locate my link. Can you point me in the right direction? Much appreciated.
     
  8. meterman

    meterman Member

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    I've noticed a bit of temperature effect on a Fulltone Soulbender...I wonder if the MkIII with its 3 germ trannies could be particularly susceptible? It was a fairly subtle thing though, still worked fine just maybe sounded flabby or weaker, maybe you've got a bad tone pot or solder joint like Mike said. I've heard of people keeping their germ fuzzes in a cooler before a hot outdoor gig but I've never tried that! Keep it out of the sun for sure, and take a silicon fuzz along as a backup....
     
  9. amz-fx

    amz-fx Supporting Member

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    Try this link:

    http://geofex.com/Article_Folders/ffselect.htm

    regards, Jack
     
  10. e-flat

    e-flat Supporting Member

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  11. QOTSA

    QOTSA Senior Member

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    The sunface bias dial does help, but that's a fuzzface circuit. Maybe something like that could be done?

    One thing I've always wondered is why there isn't a separate bias control for each transistor - would that be redundant? Mike?
     
  12. StompboxMan

    StompboxMan Member

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    Who plays in direct sunlight? Maybe all outdoor stages should always face east so if you go on after noon or later there's no sun falling on your pedals. :)
     
  13. amz-fx

    amz-fx Supporting Member

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    A way to deal with the temperature change is to add a servo circuit that controls the bias voltages. I played with this years ago but it removes some of the character of the pedal in the process so I dropped the idea.

    regards, Jack
     
  14. analogmike

    analogmike Gold Supporting Member

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    Our Peppermint fuzz has the external BUZZ knob for biasing the 2nd tranny and an internal trim pot for the other one, which you can easily bias by ear. The Sunface does not need that, the trans we use are stable enough.
     
  15. pipedwho

    pipedwho Member

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    Obviously not very battery friendly, but has anyone tried using an 'oven' heating element to keep the Ge trannies at a constant temperature? This, of course, assumes that the Ge still sounds good at the elevated temperature.
     
  16. amz-fx

    amz-fx Supporting Member

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    As the temperature goes up, so does the leakage...

    http://www.muzique.com/news/?p=97

    regards, Jack
     
  17. gang twanger

    gang twanger Member

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    Has anyone tried making a pedal cozy? You could use yarn or spin some wool. How about a fur-lined leather one?
     
  18. Lance

    Lance Member

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    Germanium likes 70 degrees or cooler. What I've done, and I got this idea from Kimock, is to keep a cooler handy, and a big Ziploc bag. Try to leave it in the cooler, until just before you play, and try to place your fuzz songs early in the set. It's about the only way to get it to sound good on an outdoor summer stage.
     
  19. gang twanger

    gang twanger Member

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    Does the cold affect Ge transistors in a bad way? I thought it did.
     
  20. Structo

    Structo Member

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    Hehehheh, that's kind of why they went to silicon transistors.
    Ge trannies are just too unstable.
    But I have the Sunface with Sundial and although sometimes I have to futz with it, it always works good.
     

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