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new Princeton sudden volume drop

Discussion in 'Amp Central Station' started by davidP7, Nov 23, 2020.

  1. davidP7

    davidP7 TDPRI Member

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    I hope one of you amp gurus out there can help me with this. I recently bought a new Princeton with a Celestion G12-65 speaker. After about 45 minutes of playing, the volume of the amp suddenly drops and it seems to me the tone gets thinner. What would cause this?

    I should add that I accidentally left the amp running for 24 hours shortly after I got it. Did I damage something? I've had the amp for about 3 months.

    Thanks.
     
  2. J. Bonkosky

    J. Bonkosky Tele-Meister Silver Supporter

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    One of your preamp tubes is bad. Probably the first position.
     
  3. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    Another vote for "most likely a preamp tube"

    Running the amp for any number of hours won't hurt anything. It's not like it's going to be hotter after 24 hours than it would be after a 4-5 hour set some night.
     
  4. schmee

    schmee Doctor of Teleocity

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    Yeah, check or just replace tubes until you find the culprit first. Try swapping one of the reverb tubes into V1 or V4 if you dont have other tubes.
     
  5. Wally

    Wally Telefied Ad Free Member

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    You could pull V2, the 12AT7, and use it to sub in for V1, V3, and V4 to see if any of those 12AX7s is bad. It would be good to have a new 12AX7 on hand...you will need it eventually anyway. V2 is the reverb driver. V3 has one triode returning the reverb and one triode processing the basic signal. V3 has one triode for the tremolo and one triode is the cathodyne phase inverter.
    You have a warranty, do you not? Although leaving that amp running for 24 hours will not harm it, I would suggest that you not mention this if you try to enforce the warranty.
     
  6. davidP7

    davidP7 TDPRI Member

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    thank for the reply guys,..
    it helped me allot.
     
  7. Dacious

    Dacious Poster Extraordinaire

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    Back in the old days before solid-state gear telephone exchanges were full of tubes that were on 7 X 24 X 365 - used to get changed after tens of dozens of hours. The techs used to drop off crates at the tip - break your heart. :mad:

    I've still got some Siemens EL34s that were pulls from an exchange swapped out on schedule, they test new.
     
  8. Wally

    Wally Telefied Ad Free Member

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    so...what did you find that was a problem. Enquiring minds and all that, right?
     
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