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Damaged tube In SVT-2PRO Question

Discussion in 'Amps and Cabs [BG]' started by ProffesB, Apr 24, 2009.


  1. ProffesB

    ProffesB

    Oct 7, 2008
    Maryland
    Hello all,
    I took a look around and couldn't find my exact situation, so please help if you are in the know.

    Background:
    I recently bought a SVT-2PRO and after 2 months of trying to get it sent to Guam it finally showed up. I'm sure you can Imagine my excitement to get it plugged in. However when plugged in and powered up I got nothing but a fault light. I would've taken it to a service center but the nearest one is in Hawaii. So I pull off the cover and discover that one of th 12AU7 preamp tube is cracked so I try and wiggle it out and the bulb comes off. I was able to get the rest of the tube out with pliers.

    Question(s):
    Is it fine to replace this tube by itself?

    This sounds like a shipping or manufacturing issue to me. What do you think?


    Thanks for your help-dave
     
  2. johnk_10

    johnk_10 vintage bass nut Supporting Member Commercial User

    Feb 16, 2008
    Thousand Oaks, CA
    John K Custom Basses
    since there is no bias or calibration procedure for a 12AU7 preamp tube, i would just replace it and see if that solves the problem.
     
  3. ProffesB

    ProffesB

    Oct 7, 2008
    Maryland
    Cool, thanks. Now lets see if I can find one on Guam.
     
  4. I'm always a bit weary of how to answer these ones.

    Sure, you could try and plug a 12AU7 in and see if it works. But chances are there has been more damage done. Either from the shipping (if it took a heavy enough hit to cause that damage), or from you turning it on when it had a broken tube. (Good reason to always give the amp a once over to make sure everything at least looks OK to start with).

    You don't need to use an Ampeg tech, any decent amp-tech should be able to give it a once over.
     
  5. ProffesB

    ProffesB

    Oct 7, 2008
    Maryland
    From the manual:

    if the tubes are bad enough to cause damage to the unit, the Fault Indicator will signal and the unit will shut down

    Since this already happened I'll try a new tube if i can find one. I'll post th results later.
     
  6. johnk_10

    johnk_10 vintage bass nut Supporting Member Commercial User

    Feb 16, 2008
    Thousand Oaks, CA
    John K Custom Basses
    while you're in there, i would inspect all of the tubes to see if any others (pre and power tubes) suffered a similar fate.
     
  7. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    If it showed a fault, that was not a preamp tube, but a driver, most likely.

    Same fix.... I support the "replace tube and check" idea.
     
  8. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    That's one nice thing about the 80's tube update in SVT's...it's got to be much easier to find 12AX7's and 12AU7's in Guam than 12DW7's and 12BH7's ;)
     
  9. ProffesB

    ProffesB

    Oct 7, 2008
    Maryland
    Unfortunately I can only find 12AX7's on island so I'll have to wait for the interweb to send me one. Hopefully I'll get it within the week.
     
  10. ProffesB

    ProffesB

    Oct 7, 2008
    Maryland
    Just an update on getting things shipped to Guam 14 days and no tube. I will go to the post office and probably be disappointed.
     
  11. ProffesB

    ProffesB

    Oct 7, 2008
    Maryland
    I'm disappointed
     
  12. johnk_10

    johnk_10 vintage bass nut Supporting Member Commercial User

    Feb 16, 2008
    Thousand Oaks, CA
    John K Custom Basses
    if you PM me with your address and i'll send you an RCA 12AU7 if you pay for the shipping (should be cheap for priority mail international-small package).

    regards,
     
  13. You are a gentleman johnk 10 !
     
  14. ProffesB

    ProffesB

    Oct 7, 2008
    Maryland
    Johnk-10. Thank you for the offer. I ordered though a second company and paid for the good shipping, according to fedex this second order should be out here wendsday at the latest. I will agree with B-string, you are too nice for the offer. Cheers-dave
     
  15. ProffesB

    ProffesB

    Oct 7, 2008
    Maryland
    So the tubes came today, I replaced the cracked one and checked all the others turned it on and nothing. However upon reading the back of the amp looking for something I noticed a sticker next to the plug that says U Export 240V. Does this mean what I think it means? Do I have to convert the amp to 120 or get a step up transformer in order to use it?
     
  16. johnk_10

    johnk_10 vintage bass nut Supporting Member Commercial User

    Feb 16, 2008
    Thousand Oaks, CA
    John K Custom Basses
    it looks that way to me.

    boy, what a string of luck you're having....!
     
  17. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    It will convert to 120V if that is what you have.......... no problem, just a hassle for you.
     
  18. ProffesB

    ProffesB

    Oct 7, 2008
    Maryland
    Well I am almost there....... I hope

    I was able to find a step up transformer on Island. Only Issue is it's only rated to 100W The good news is the amp turns on and plays.

    The bad news is the small transformer blows a fuse anytime the volume gets usable, I will have to check some other places then off to the internet I go. Also one of the green bias LED's will not light, goes from none to red, The book says one or more tubes may not be working so I'm a gonna make sure they are all seated well.
     
  19. just swap the power tranny's taps over to 120.....I did the opposite w/ an SVTII from USA to Australia. Pretty EASY IF U know elecs a bit (more than I)
    :)
     
  20. ProffesB

    ProffesB

    Oct 7, 2008
    Maryland
    I'll check that out. I am an electronics technician after all, I just had no idea where to start with a tube circuit.
     

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