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1976 Fender Twin Reverb Overhaul

Discussion in 'Amp Tech Center' started by keithb7, Feb 13, 2017.

  1. keithb7

    keithb7 Friend of Leo's

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    Here's the final total of what I pulled from the amp. Yes, hose clamps, also known as tube retainers. LOL.

    [​IMG]
     
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  2. FenderLover

    FenderLover Poster Extraordinaire

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    ^^^^Yikes....!!!
     
  3. Snfoilhat

    Snfoilhat Tele-Afflicted

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    I'm curious how much variability in tone/EQ/noise you are getting across the sweep of a 1K NFB adjustment. My current amp has a different NFB injection point (because it's cathodyne PI not LTP) and different OT'', dropping resistor, etc., so maybe not a good basis of comparison. But I'm using a 100K and enjoying the variety.

    And I thought Wally suggested 10K, which is why I'm asking.

    Thanks!
     
  4. keithb7

    keithb7 Friend of Leo's

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    Wally suggested a 5K. That is actually what I put in there. I was shooting from the hip while recording the video and said 1K in error.
    With the 5K in there I am hearing little to no difference while adjusting the NFB resistance.
     
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  5. 24 track

    24 track Doctor of Teleocity Ad Free Member

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    Nice work!,Nice work!

    you should sell him back the parts you removed incase he wants to make it original......:D
     
  6. brogh

    brogh Moderator Staff Member

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    Oh Wow !

    besides repalced items did you get a clue on what was done on the amp ? i mean have you figured out what the attemp was in throwing all the extra stuff in ? kinda curious now...

    Great Work Keith ! the owner is gonna be pretty happy :)

    Cheers
     
  7. Paul G.

    Paul G. Friend of Leo's

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    I had forgotten just how fat a SFTR sounds. Lovely job on that bringing one of these treasures back to life.

    There was a rehearsal studio I used to use that had a MVSFTR with Celestions in it that I made a beeline for every time I was in there.

    P.
     
  8. Kev Reg

    Kev Reg Tele-Meister

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    Man that thing sounds beautiful! Great thread. Great effort.
     
  9. keithb7

    keithb7 Friend of Leo's

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    That's the one regret I have with this project. I never even plugged it in to hear it and try the mods before I dug into it. The owner told me the amp worked but I was disgusted with what had been done to a killer vintage Fender amp. I just got to work. I was on a mission right from the minute the owner walked out the door after dropping the amp off. It appeared to me that someone was sold a package of goods on how the TR could be made better. I had mentioned some of the mods in post 1. There was a DI line out. All vibrato removed. There was an additional small transformer that powered a relay. A pull pot was installed in channel 2 input 2. I believe this was a pull pot to engage a fuzz mod. I cannot be sure what was going on with the tone stack wiring. When I wired it to AA270 I had to move lots of wires. There were extra small pF caps in the circuit too. The pile of parts is not all mod parts, some were parts that just needed to be changed with a full service. Also in the pile were the 4 power tube sockets and the Canadian thermal breaker that I yanked out of the amp.

    I have been demoing the amp for the past 24 or so hours and its solid. It sounds just like my 1973 Twin (that I just sold) and other SF Twins I have serviced. The AA270 tone stack wiring is somewhat interactive. When all the EQ pots are on zero you get no sound, regardless of what the amp volume pot is set at. It's cool. You can roll up one pot at a time and hear exactly what is going on with that dial. In my opinion running the TR on 2 only power tubes is a tragedy. The amp sounds so much thicker and fuller, fatter with all 4 power tubes in it. A 4 tube TR is where it's at. To me its kind of like running a muscle car on only 4 cylinders to save fuel. Sure it looks good, but sounds and performs lousy. I elected to pull out the 5K variable NFB mod and stay with the 820 ohm stock fixed NFB resistor. The 5K mod was offering very little tonal differences. I put an old dead pot in the hole and left is unwired. So the sound guy and walk up and stage and adjust the MV as he sees fit. LOL.
     
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  10. 24 track

    24 track Doctor of Teleocity Ad Free Member

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    Looking at your post again i wonder if the same guy who did your mods was the same guy who did the mods on this 74 super reverb I did it looks like the same hack wiring and cheap parts.

    P1011217.JPG
    P1011219.JPG
    P1011220.JPG P1011221.JPG
    P1011224.JPG

    Really nice work you did, there
     
  11. FenderLover

    FenderLover Poster Extraordinaire

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    Keith, what if it was an Alexander Dumble modded amp, and you just defaced it to the tune of $5K ;)
     
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  12. jazzguitar

    jazzguitar Tele-Afflicted

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    If it had been a Dumble mod, the inside of the amp would have been full of black goo.
     
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  13. adjason

    adjason Poster Extraordinaire Silver Supporter

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    Well done - it sounds good to me
     
  14. SacDAve

    SacDAve Poster Extraordinaire

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    Nice job, You have to love that Fender reverb sounds great.
     
  15. brogh

    brogh Moderator Staff Member

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    24 track

    now we want to know more about your VSCH (variable size chassis holder) that's brilliant ;)
     
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  16. whiteop

    whiteop Tele-Afflicted

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    Sounds great and it says a lot about you to do that pro bono. Awhile back I helped a kid at my church get a Tele that I modded for him then later sold one of my guitars and used some of the proceeds to get him a Fender Hot Rod Deluxe III (the new ones without the problems). I could tell it boosted his confidence because he got a lot better all of a sudden. After that he went and tried out for the Voice and made it through several cuts but didn't quite make it onto the show. Still you could tell his confidence grew.

    So you can never tell what one act of random kindness can do. May it come back around to you later...:)
     
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  17. Bill Moore

    Bill Moore Tele-Afflicted

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    Thanks for the post, I just picked up a 79 MV Twin that I plan to put back in usable shape, (when I finish my current project). I think the only mod to it was disconnecting the export voltage selector.
     
  18. haggardfan1

    haggardfan1 Friend of Leo's

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    Great restoration and an entertaining narrative, as always. Thank you Keith.
     
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  19. BobbyZ

    BobbyZ Doctor of Teleocity

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    That's not a 74 ! Judging by the parts I'd date that about 1967ish. That's about the time they went to those cathode bypass caps and still had the blue Ajax caps.
    A 74 would have blue blobs like Keith's and white Mallory bypass caps.
    That's a late blackface/very early silverface.
     
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  20. 24 track

    24 track Doctor of Teleocity Ad Free Member

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    I knew it was one of the early silverface units basically a black face with silver front on it , As keith and I live close to each other and the MO seamed much the same it struck me that the soldering monkey that had its way with the unit I fixed could be the same as the one that made a mess out of the unit keith fixed, thanks for the confirmation!
     
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