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How do I take apart my SVT?

Discussion in 'Amps and Cabs [BG]' started by jacksonev94, Mar 30, 2015.


  1. jacksonev94

    jacksonev94

    May 12, 2012
    Lynchburg, VA
    I need to take my '71 SVT apart to replace the pre amp tubes and give her a thorough cleaning with Deoxit. How do I do this without a) shocking/killing myself and b) hurting my baby?
     
  2. tallboybass

    tallboybass Supporting Member

    Feb 25, 2003
    Tulsa, Oklahoma
    My thought is...if you have to ask that question, maybe it would be better to go to a professional.
     
  3. Tubes should be easy enough to get to with a screw driver. They are ''user service'' items.

    Ratting around in the guts, not a good idea.

    44 year old amp deserves a bit of professional tlc no?
     
    B-string likes this.
  4. I agree with the Tech solution. There can be lethal voltages in the chassis even with the power off.
     
    B-string and stigbeve like this.
  5. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Bah, just don't touch anything you shouldn't and don't have it plugged in while you reach inside and you'll be OK ;)

    You have to take the back screen off to get to the tubes, but you can get to all of them easily enough when you do.
     
  6. Rugmaster

    Rugmaster

    Dec 6, 2012
    Like everyone said, just take the back grill off using a Phillips head screwdriver and a socket wrench. If you need to take the power amp out, just unbolt the screws on the bottom of the amp and it should slide right out.
     
  7. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Once you have the back metal grille off...

    Unplug the fan.

    There is a cable assembly running from the pre to the power amp. It unplugs at the power amp. Remove the power amp. Big bolts on the bottom. Turn the cabinet on its side when doing this. It is very heavy so be careful when sliding out the power amp. You don't want to drop ot or smash the tubes. It helps to work on the floor if you don't have a workbench. The front grille frame pops off with a bit of force.

    Flip the amp over. Inside there is a row of screws holding the pre in place. Remove them the the pre slides out. You now have access to the inside of the pre.

    Note that electrolytic caps remain charged even when the amp is turned off. There is a way to discharge them. Here is a reference: Technical - Amplifier - TalkBass Wiki
     
    Last edited: Apr 1, 2015
  8. BurningSkies

    BurningSkies CRAZY BALDHEAD Supporting Member

    Feb 20, 2005
    Syracuse NY
    Endorsing artist: Dingwall Guitars
    Get in there with a screw driver and start poking at connections.
     
  9. rickdog

    rickdog Gold Supporting Member

    Mar 27, 2010
    If you really need to replace the preamp tubes (not the drivers in the power amp, visible in the back), I think removing the four screws on the top of the case will allow you to slide the preamp forward (carefully) far enough to change the tubes. Don't touch anything but the tubes and you should be safe! Note: I've done this on my SVT-CL, not a vintage SVT, so yours might actually not be like mine.

    But, as others have pointed out, a '71 SVT is probably long overdue for a checkup by a tech with appropriate skills and a good reputation. It will cost you a fraction of what repair or replacement would cost if something fails catastrophically. And those vintage preamp tubes might test just fine!
     
  10. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Rick, your CL is not at all like his ;) To get the preamp out of the old ones, you take the back off and unscrew the screws from the inside top of the headcase that hold the preamp in, then undo the molex connector for it and slide it out the back.
     
  11. waltdogg

    waltdogg

    May 24, 2014
    Not an expert or vintage SVT owner. But isn't the chassis for the preamp on a vintage SVT setup like a V-4? The preamp tubes hang down and are visible from the rear of the amp with the back grill taken off. There might not be enough room to reach in. But seriously, the least amount of disassembling means the less likely you are to goof something putting it back together.
     
  12. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    That is true, but the guy also said that he wanted to clean the knobs and switches with Deoxit while doing the tube changes, and that's the best way to get at them. It's not very difficult to do and has a very low risk rate, either with getting electrocuted or putting it back together the right way.
     
  13. waltdogg

    waltdogg

    May 24, 2014
    I'd spray the pots from the front (as it's easy to miss the little slots on the backside of the potentiometers and end up spraying DeoxIt all into the pre-amp chassis, then you're poking around in there trying to wipe it all up) until I was comfortable working on such a beastly amp, which I am. But for OP's sake. I'd hate for 'em to wreck the amp or injure themselves on a basic repair.
     
  14. rickdog

    rickdog Gold Supporting Member

    Mar 27, 2010
    OOOPS! :oops: Sorry for the bad advice, looks like I'm the April Fool this year! I'll slink back to my doghouse and just read and learn about amps I don't have!

    Thanks for the quick save, Jimmy!
     
    JimmyM likes this.
  15. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Quite alright...if I had a dollar for the things I said on here that I got corrected minutes later, I could own a bank ;)
     
    Electricblue likes this.
  16. Jim Carr

    Jim Carr Dr. Jim Gold Supporting Member

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
    Can't you just lower it into a boiling vat of trichlorethylene? That's what we used to do in the old days—and we liked it! :thumbsup: :thumbsup: :thumbsup:

    Oh wait, those were SBT (steel braider trolley) heads, not SVT heads, sorry for the mix-up. :whistle: :whistle: :whistle:
     
    Last edited: Apr 2, 2015
    johnpbass and JimmyM like this.
  17. jacksonev94

    jacksonev94

    May 12, 2012
    Lynchburg, VA
    Wow, thanks for all of the feedback, everyone! I think I'm going to go with the tech option, just to be on the safe side. I called a nearby one up, and he's going to let me watch/participate while he does his thing, that way I can learn some of the basics.
     
    B-string and S-Bigbottom like this.
  18. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Some techs will charge you more if you watch. Even more if you help. :laugh:
     
    agedhorse, johnpbass and JimmyM like this.
  19. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Nice of him to do that for you. You'll see it's not so mysterious and spooky after all.
     
  20. MR PC

    MR PC Banned

    Dec 1, 2007
    If you don't mind the possibility of being thrown across the room from the zap you'll get from touching the wrong part at the right time, by all means save a few dollars and start poking around..and be sure to have you affairs in order for the funeral...:)
     

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