Stupid Question About Installing SVT in Head Box

Discussion in 'Amps and Cabs [BG]' started by Top_Ten, Jul 22, 2018.

  1. Top_Ten

    Top_Ten Supporting Member

    Jun 14, 2008
    San Francisco Bay Area
    OK, I know I should be able to figure this out on my own, but can anyone give me the lowdown on how an SVT screws into the head box?

    Here is my situation:

    I have a mid-70s SVT that is in good working shape but has a really thrashed head box -- like the wood is disintegrating in places. I bought a new head box from Fliptops, but it is not obvious from looking at the amp exactly how the head screws into the head box.

    I know the power amp section and the preamp section of SVTs are in two separate pieces, and I can see that the power amp section appears to just screw in from the bottom of the head case. But I can't tell from the outside how the preamp section attaches and I don't want to start taking it apart until I understand better how to put it back together.

    Any help? Thanks!
    pglaser01 and Rumbledore like this.
  2. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    Is your current preamp not screwed into/attached to the original case? I would think disassembling the original would require removing a few screws (and by assume I mean it will) which should make it pretty clear how it’s attached.

    Look inside the case with a flashlight if necessary. The screws are along the edge of the preamp section.
    Savage_Dreams likes this.
  3. BadExample


    Jan 21, 2016
    Now that's good thinking!

    Can you make a pattern off the old head case? My old head case is sitting beside me eating ice cream, so I have to be careful how i word this :D

    Maybe do something like: get a large piece of heavy paper and tape it to the old head case, aligned evenly with the front. Maybe an unfolded grocery bag. Mark or cut evenly with the sides and back. Use a dull pencil to trace the screws onto the paper. Once you get the guts out of the old case, you can use those to verify the accuracy of your tracings. Then you have a pattern you can line up on the new case and gently center punch the traced screw points.
  4. Top_Ten

    Top_Ten Supporting Member

    Jun 14, 2008
    San Francisco Bay Area
    Thanks for the replies. The part that is throwing me is the preamp section. It is not obvious from looking at it where the screws are that secure it to the headcase. I don't think my amp is any different from any other SVT of that vintage, so I am hoping that someone who has dealt with this before can provide a brief description of how the preamp screws into the headcase.
  5. bobyoung53

    bobyoung53 Supporting Member

    The pre-amp section slides in from the front (I think, it's been a while, maybe from the back) and then when you get it in position there are 4 or 5 screws that screw into the top of the box, maybe there are no holes since yours is new.
    Wasnex, Top_Ten and JMacBass65 like this.
  6. I own a 76 SVT, and have pulled it apart a couple of times. Do you have the back panel off?? If you don't, unscrewing it and pulling it off should make it all clear as day. The preamp section, IIRC, sits on a couple of wooden rails mounted on the sides of the interior, and then there are smallish screws, maybe 6 or 8 of them, that screw the back edge of it (it's wedge shaped) into the top.

    I think for disassembling you will want to take the power amp out first. Warning, it's heavy AF, then turn the thing upside down to take the pre amp mounting screws out.

    By the way - if you are doing a restore job, and have a tattered grill cloth that you are considering replacing, I'd happily take the cloth off your hands. I know it can be bought new - but my SVT and cab are so ragged out, I'd rather have old cloth. My was lost back in the day when I painted the whole thing neon green (since undone).....don't ask. :rollno:
    Top_Ten, bobyoung53 and BadExample like this.
  7. beans-on-toast


    Aug 7, 2008
    Remove the power amp from the bottom. Now it’s a lot easier to see the pre. It will be obvious how the pre is screwed down.
    Top_Ten, JMacBass65 and bobyoung53 like this.

    You can see the rails just above and to the far right and left of the grill. They are short.

    And in this next picture you can see, above the writing the six screws that hold it in place. Those screws also serve to hold the preamp casing together along that edge as well, so be aware when you pull it out.

    bobyoung53 and Top_Ten like this.
  9. Top_Ten

    Top_Ten Supporting Member

    Jun 14, 2008
    San Francisco Bay Area
    Thanks so much everyone -- that is exactly the info I needed. Much appreciated!
    JMacBass65, bobyoung53 and BadExample like this.
  10. BassmanPaul

    BassmanPaul Inactive

    Take a few photos with your phone during the disassembly so you have a pictorial reference.
  11. I’d do a quick search on YouTube. Almost guaranteed, somebody has a video showing you just how to get an Ampeg apart.
    JMacBass65, Aqualung60 and BadExample like this.
  12. elgranluis


    Feb 14, 2003
    Vail, CO
    I had the same issue with my svt. I can’t exactly rememberer how I took it apart , but when putting the preamp back into the box , the six screws simply will hold the pre from the rear and the front will basically drop. The mesh plate on mine wasn’t enough to keep it in position (still sagged somehow ).

    I ended up cutting a small piece of pine that would fit from bottom of cab to preamp, been happy ever since.
  13. anderbass


    Dec 20, 2005
    Phoenix. Az.
    I've been searching for the key to happiness for a long time,
    who woulda thought it was just a small piece of pine ~ ;)