Strange Phenomena

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Troy T. Blues, Jan 30, 2012.

  1. Troy T. Blues

    Troy T. Blues Comstock Station

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    I have two older 100W Marshall heads that I bring to rehearsal. Both of them experience the same issue. They cut out big time and/or don't work at rehearsal and then when I come home, they work fine. The only thing that is different is that I change from 8ohm at home (2x12) to 16ohm at reheasal becuase I use my friends 4x12 cab there.

    I've plugged straight in, tried different speaker cables, different speaker inputs, different cabs, different outlets, different guitar cables, different guitar, you name it! I've used my JMP 2203 most times and we eventually get it to work. Edit - (The 2203 had a seperate similar issue, but it has been resolved) Sorry about that.

    Yesterday I brought my 1975 Super Lead for the first time and it just kept cutting out or no sound at all. I even tried swapping 12AX7's. Yesterday it almost sounded like a blown transformer, but when I bring it home, it's fine! I was really bummin' yesterday thinking that the amp was cooked. WTF is going on? We even tried using my friends other 4 x12 cab, in a different outlet, etc and still the same results! This is the stangest thing I've ever encountered and it's really starting to piss me off now. I've wasted alot of time messing around with this too.

    Any ideas/help would be greatly appreciated. This is puzzling!!!! :FM :huh
     
    Last edited: Jan 31, 2012
  2. mcdes

    mcdes Member of no importance

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    I would look at the common denominator. What they are powered by, or plugged into, or maybe the guitar end, what's going into the amps..... Problem with guitar to pedal board, then to amp? Process of elimination.
     
  3. '58Bassman

    '58Bassman Member

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    Test the circuit. You can buy a circuit tester for less than $10 and it will tell you if the three wires are connected correctly, if something is crossed or open.

    The cabinet has nothing to do with this.
     
  4. TweeDLX

    TweeDLX Member

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    +1 on the circuit tester!
    Is this happening to anyone else at the rehearsal space, or just you? Can you describe your exact set-up, from the guitar/cable...down to whatever is between the amp and the wall socket. I had a similar problem with my rig cutting out that turned out to be a bad power supply (wall wart) to my pedal chain). This may not be your problem, but leaving "no stone unturned" is the only way to narrow it down.
     
  5. Troy T. Blues

    Troy T. Blues Comstock Station

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    That's true. After some more thought and speaking to some other people, it must be something in the circuit. What could it be about the circuit that would cause this though? Thanks
     
  6. ked

    ked Supporting Member

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    Take a look at the impedance selector, it may not be making a good contact, causing the amp to cut out.

    Ken
     
  7. schmidlin

    schmidlin Member

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    Does the indicator light stay on when it cuts out?
     
  8. Troy T. Blues

    Troy T. Blues Comstock Station

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    It's only happening to me and it's very hard to explain. I've done a lot of troubleshooting. I've got the 2203 to work, but it has happened in the past. The pedal board is out of the equasion at the moment.
     
  9. Troy T. Blues

    Troy T. Blues Comstock Station

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    Good point. It's the old style one - rotary where you pull out and then push in.

    Yes, the indicator light stays on.
     
  10. Peteyvee

    Peteyvee Premium Platinum Member

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    $100 says that's the culprit. Clean it with contact cleaner and make sure it seats well or you will mess up the amp(s).
     
  11. Troy T. Blues

    Troy T. Blues Comstock Station

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    I think so too...thanks. I will start by using some DeOxit. Hopefully that does the trick.
     
  12. QRSS

    QRSS brutalist

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    well, why then is it happening with the 2203 also?
     
  13. phsyconoodler

    phsyconoodler Member

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    "The only thing that is different is that I change from 8ohm at home (2x12) to 16ohm at rehearsal becuase I use my friends 4x12 cab there."

    That's the only thing different.Are you sure you are plugging into the '16 ohm only' speaker jack on the back of your head?

    And,did you test your friend's speaker cab to make sure it's actually 16 ohms?
    It seems to me you are totally overlooking something very obvious here.
     
  14. mc5nrg

    mc5nrg Supporting Member

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    get the impedance selector fixed before you blow the amps.
     
  15. Troy T. Blues

    Troy T. Blues Comstock Station

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    I'm sorry guys. I believe the 2203 was a different issue and has been rectified. There is no 16 ohm only jack on the '75 Super Lead head. I did not double check to see if my friends cabs are wired in 16 ohms, but I am assuming they are and I tried both of his cabs. He uses them with no issues. I'll spray DeOxit and try it one more time over there next week. I hope that the contact cleaner will fix the problem until I can get it fixed/upgraded.
     
  16. Troy T. Blues

    Troy T. Blues Comstock Station

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    After doing some research, I found this and also a friend basically told me the same thing. Hmmm....

    "I bend the legs on the adapter just a very little so they are hard to insert and thus never falls out. I have been playing my '75 super lead for about 10 years, switching between a 16 ohm cab and a 8 ohm cab and never had a problem".
     
    Last edited: Feb 3, 2012

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