SVT problem

Discussion in 'Amps and Cabs [BG]' started by Paddy515, Sep 10, 2018.


  1. Paddy515

    Paddy515

    Sep 10, 2018
    Hi all - 1992 svt 2 non pro developed a cut out fault after being played for about 5 minutes - sound fades and head makes a shrill sound. Anyone any thoughts as to the possible problem? Cheers all.
     
  2. Double E

    Double E I ain't got no time to play... Supporting Member

    Dec 24, 2005
    Cleveland, OH
    Some connection is failing as the amp warms up... loose solder joint or bad part. Take it to an amp tech. You ought not be attempting to use it in the meantime in case there's potential for making it worse.
     
    cerrem and Paddy515 like this.
  3. Paddy515

    Paddy515

    Sep 10, 2018
    Thanks chief - am going to do so, cheers.
     
  4. Paddy515

    Paddy515

    Sep 10, 2018
    Anyone any other thoughts?
     
  5. JACink

    JACink

    Mar 9, 2011
    Spain
    You mean you want a second opinion on whether to take it to a tech?

    Yes, take it to a tech ;)
     
    Munjibunga likes this.
  6. BogeyBass

    BogeyBass Inactive

    Sep 14, 2010
    It's a SVT

    You'll get use to it lol
     
    Paddy515 and JimmyM like this.
  7. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    Shrill sound makes me think there's a bad tube. You could try tapping each tube lightly with a light wooden (for obvious reasons) stick while it's turned on and plugged in to see if you can spot a bad tube. The only other problem you could check out on your own is corrosion in the preamp in/out jacks. I had a rental SVT a couple nights ago that had this problem and the volume was cutting out. I fixed it by running a plug in and out of the jacks several times fast. However, there could also be other reasons, and if these things don't work out, taking it to a tech is of course the sensible thing.
     
    Paddy515 likes this.
  8. neckdive

    neckdive

    Oct 11, 2013
    I have an 89 SVT II that was experiencing some intermittent cutout issues. Similar to Jimmy's advice, try this first before you take it to a tech.

    Plug one short 1/4 inch cable into the preamp in and out jacks on the back of the head (Left side, next to XLR out). This simple thing eliminated the problem completely and now I just keep the cable plugged in all the time just to avoid any problems that may crop up during a show.

    It hasn't cutout since.

    IMG_4109.PNG
     
    basscapes likes this.
  9. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    Clean the jacks with Deoxit or by the plug method I posted and you can skip the cable. Just a matter of getting that corrosion out of there so you get good contact.
     
    basscapes likes this.
  10. neckdive

    neckdive

    Oct 11, 2013
    All true. The cable is good for troubleshooting as it isolates the issue and positively identifies it as corrosion in the jacks.
     
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  11. I have never heard of a shrill sound coming from a bad jack connection. That sounds more like something a tech should investigate.
     
  12. callofcthulhu

    callofcthulhu

    Oct 16, 2012
    When my SVT-CL wailed like a digital banshee it was a dying preamp tube.
     
    basscapes likes this.
  13. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    I think it's most likely going to be a microphonic tube, and I think callofcthulhu is right about it being a bad preamp tube. I've heard plenty of shrill sounds from them. They would be the first ones I check. However, the sound fading could be dirty preamp jacks, and that's why I suggested taking a look at them while he's at it, especially since they and the tubes are pretty much the only user-serviceable parts.
     
    basscapes likes this.
  14. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    What you are describing, fading and high pitched sound, is often an issue with a pramp tube. Here is a guideline as to when to change tubes, note the symproms:

    Tubes | TalkBass.com

    It never hurts to have all the metal-on-metal contacts, including jacks, tube pins and sockets, cleaned with Deoxit.
     
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  15. Paddy515

    Paddy515

    Sep 10, 2018
    Guys - head back from the tec. Diode was to blame. Swapped out - full check over and long run. £30 GB pounds. Thanks for all your advice. Back to its earthquaking best.
     
  16. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    Interesting...I will have to remember that if someone else has a similar problem.
     
    Paddy515 likes this.
  17. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Excellent, and the repair cost was reasonable.

    Often the sign of a bad diode is distortion.
     
    Paddy515 likes this.
  18. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Jun 15, 2021

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