SF Twin Reverb

Discussion in 'Amps and Cabs' started by bgutschow, May 6, 2016.

  1. bgutschow

    bgutschow Member

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    I was feeling exceptionally muscular the other night and decided to take the Twin Reverb to rehearsal. I don't know the exact year but it is mid 70's with JBL D120's in it. Push/Pull MV, not the ultra-linear.

    Everything sounded as clean and bright as ever, however the low-end sounded kind of "farty". It was re-tubed a couple years ago, the caps have never been changed. Any ideas what to look for before I take it to a tech?

    Thanks!
     
  2. Stratonator

    Stratonator Member

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    Possible speaker problem? Try it in another cab.

    Could be a tube issue. Try other tubes in V1 and V2.
     
  3. Steppin' Wolfe

    Steppin' Wolfe Member

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    Ime, that amp needs to be recapped. then, you decide what else to do...tubes? One sonic indicator of weakening caps is a farty, out of tune low end.
     
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  4. pbmw

    pbmw Member

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    If it has a pull boost, it's at least a 77. If it hasn't been cap'd, I'd suspect the power supply caps first.
     
  5. bgutschow

    bgutschow Member

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    Thanks for the info guys.
     
  6. custom53

    custom53 Member

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    Yes, take it to a tech.. My '74 SF Twin Reverb sounded great after I had a tech go thru it.. Not that it sounded that bad before..

    [​IMG]

    [​IMG]
     
  7. zebuloncamp

    zebuloncamp Member

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    I could be wrong, but I think 73 was the first year with push pull master volume. 77 is the year they went 130 watt ultra linear though.

    Could be a lot of things, but, if you're going to keep the amp might as well go ahead and get a cap job done when time and money permits. Then it will be ready to roll for a while!
     
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  8. zebuloncamp

    zebuloncamp Member

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  9. TheWayfarer84

    TheWayfarer84 Silver Supporting Member

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    definitely needs fresh caps.
     
  10. pbmw

    pbmw Member

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    You may be right I know 77 was the first pull boost for SFPR's and they were some of the last to be changed by CBS, but I thought the PB's were a little later.
    You learn something new every day...
     
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  11. bgutschow

    bgutschow Member

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    Thanks again guys, I'll call a tech. Not sure of the year, all I know for sure is I purchased it used in 1977 for $350.
     
  12. dcbc

    dcbc Member

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    72 was when they went master volume. 76 for pull boost. Late 76/77 for Ultra Linear 135 watt ouput transformer. But with all things Fender, they used up the old stuff before starting the new stuff. So I suppose it's possible that he has a 77 with the old style output transformer, but with a pull boost.
     
    Last edited: May 11, 2016
  13. zenas

    zenas Member

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    They had the pull boost for several years before they went ultra linier.
    I've got a very late non UL SFTR I bought from the original owner. He said it's a 77 but I've never bothered to try and date it.
    It's one with the higher blackface type plate voltage and not the lower ones they made during the silverface years. I've never cared for those.
     
  14. dcbc

    dcbc Member

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    From all I have read and seen, pull boost and the UL/135 watt Twins were within a year or so 76/77. But it's not uncommon to have mix and match transformers, i.e., a 100 watt non-UL transformer in a 77.
     
  15. zenas

    zenas Member

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    Schematics are pretty hard to come by for all the different silverface Twin Reverbs. I didn't find one for mine. It has the hum balance pot.
    Dammed near every master volume one I've ever seen had the pull boost. Which leads me to believe it was used for several years.
    The other pull boost SFTR I had was supposed to be a 75 but again I never bothered to date it exactly. It didn't have the hum pot.
     
  16. zenas

    zenas Member

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    zebuloncamp likes this.

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