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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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    Thanks for the kind responses folks. The owner came and picked up his amp last night. He was very, very happy with its tone. He claimed that the amp was dark, and broke up very early. He writes music and performs in an original band. He uses no effects, only a clean Tele, straight in. So the end result of this restoration met his hopes. Of course after we demo'd his amp I invited him to try whatever of my vintage amps that he wanted. 2 hours later, we had been though most of them. He asked lots of questions. I poured on the info. I educated him in Fender amps and the heritage of Leo Fender and Co. He was particularly interested in his new and exciting vibrato, now present in his Twin. I pulled his chassis and showed him the roach. I answered lots of his questions about the guts of his Twin. I went as far as making him try all 3 types of Fender vibrato in various amps of mine. Harmonic, Bias Wiggle and LED Roach style. He had no idea, and said he loved them all. In the end the mighty HPTT was turned on and we both shook our head in wonder. He left happy with his amp...I think. I may have wrecked another young aspiring guitar player. It happens.

    24 Track we are close, you're right. Could be the same hack in both these amps. We might have a serial amp killer running amok in town. See the black cathode caps? Those are Whale brand. From my experience, I have only found these Whale caps used in Fender amps after CBS took over Fender, early in the game. I believe by 1969 they had switched to White Mallory cathode caps as BobbyZ pointed out. I have read bad reviews about Whale caps, but can't speak from my own experience. I remember reading a story where CBS purchasers saved the company a bunch of money by sourcing cheaper caps from Jamaica. For use in amp assembly at the factory. The story went on to say the quality was poor, but did not name the brand. I often wonder if it were these Whale caps? Mallory makes a good cap and is still around today. Whale? Gone I think.
     
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  2. 24 track

    24 track Doctor of Teleocity Ad Free Member

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    Thank you!
    I saw some thing like it on Ebay for a ton of dollars so I bought a shelf glide and built 2 of these , the top where the chassis sits has a pin that sits in the holes where the screws mount for fender amps and holds it so it will not expand while the amp is being held .
    Matereials: 3/4" pressboard
    specs:
    6" wide 9" tall 17.5" folded (outside) (16' inside ) opens to 32" (inside) 33.5" (outside)

    Parts
    (I used scrap pressboard )
    2X 6"X9" sides
    2X 6"X16" (split bottom)
    2X 6"X1.5" (top lip to hold the amp)
    1X 16"x32" shelf glide
    glue , screws, 2 metal pins, and padding to prevent scratching to the amp.

    total build time 1.5 hrs even less i was designing as i went, no drawings
     
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  3. 24 track

    24 track Doctor of Teleocity Ad Free Member

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    I have a caveat to the repairs i did to the Super, the owner gave me a ton of equipt including a late 60's-early 70's Sunn Sonaro amp and cabnet , 2 mixers and a bunch of other stuff ( he was moving and had no room for it) If he were to ever part with the Super I get first kick at it! supers are my first choice in amps I love them! especially the early ones
     
  4. 24 track

    24 track Doctor of Teleocity Ad Free Member

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    Cool stuff Keith, great post , thanks for sharing , I learn crap loads from these types of posts
    Well done!
     
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  5. moosie

    moosie Doctor of Teleocity Silver Supporter

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    Keith, I just read the whole thread. I had seen the initial post with the pile of garbage yanked out, but I didn't subscribe, and it fell off into the ether...

    I might have made that same rookie call, to rewire the whole darn thing. I HATE that plastic wire. My '69 Twin has cloth, and the '71 Super I'm servicing now (slowly) has crap, er plastic. I won't say I didn't consider it! :rolleyes:

    What I'd like to know is how the kid was playing this amp with no filaments in his power tubes...

    Very nice thread, nice job on the amp, and glorious tone!

    Did you track time spent?
     
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  6. keithb7

    keithb7 Friend of Leo's

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    There he is! My friend Moosie finally checked in. So glad. I wondered what happened? Was he sick of my vintage amp gloating? LOL?

    I did not keep track of my time Moosie. I went pretty slow though. I enjoyed the rebuild process as much as I could. I wanted to inhale all that solder smoke slowly like an after dinner cigarette. I was diligent at times re-doing things. It still could have turned out better. Like the guitar player in me always thinking after a solo, I could have done it better. I estimate I spent 15-20 hours tinkering away in the amp over a 2 week period. I must admit my time was not entirely spent efficiently. Gotta check in on Tdpri every so often you know. ;) I did a fair amount of research and backed up my thought process by searching the internet as I moved though some areas of the amp. Due to the fact that I was converting a later 1976 circuit back to an AA270 mainly. I took a ton of close up circuit photos, from several angles of my 1973 Twin Reverb right before I sold it. That was about a week before I took on this 1976 amp restoration project. I used those 1973 TR photos as a reference many times through the restoration. I was not starting with a good specimen with the 1976 TR. As you saw, I gutted a lot from it. Stuff was long gone before it got to me. Like the entire vibrato circuit for example.

    The bad power tubes, the filaments thing still stumps me too. I turned the amp on for the first time and I had no filament glow and no sound of course. I pulled the pair of 6L6's and tested them in my thermionic tube tester. No filament glow either. I put in a spare pair that I had and they lit right up and the amp made sound right away. Later during testing and tweaking, I put the dead 6L6 tubes back in to try them again for some reason... They worked. WTH? I then proceeded to test the amp for a few hours, over a few days and the original tubes were fine. I can't explain it. So I shared the experience with the owner and told him he should consider running the amp with 4 tubes, as I felt it sounded better. The reliabilty of the original tubes was questionable. The age of the original tubes was unknown. I suggested he buy a matched quad or two matched pairs, and keep the originals as spares. I would install and balance the new tubes if need, for free.
     
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  7. Blue Bill

    Blue Bill Poster Extraordinaire Ad Free Member

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    Sounds great, nice job!
     
  8. moosie

    moosie Doctor of Teleocity Silver Supporter

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    You should have used something indelible to write on the inside of the chassis.

    DON'T EVEN THINK ABOUT IT - KEITHB7
     
  9. keithb7

    keithb7 Friend of Leo's

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    Time to put the final ribbon and bow on this thread. I drove up to our local ski resort to the village tonight to hear this '76 TR in action. The owner and his band were playing live at a pub. The place was packed. It was a double header gig. 2 bands. The other band, also playing original material, their 20-something guitarist just bought my 1973 TR about 3 weeks ago. So both amps were on stage and in use at the gig. Both sounded great. I don't think I can ever recall being in the audience and enjoying an un-mic'd Twin Reverb. They sound wonderful. The artists did a great job pulling great tone from the amps. There's hope folks, for the next generation with tube amps. These kids are over the moon with their Twins. Big smiles and great tone. Here are both amps are in action. My old '73 on top. The '76 that I rebuilt to 1970 specs on the bottom. I'm proud of these kids. They respect and love their big old Twins.

    I'm kind of regretting selling the 1973 a little, but the kid wanted one so bad. It went to a great home. I'll find another.

    [​IMG]
     
    Last edited: Mar 5, 2017
  10. moosie

    moosie Doctor of Teleocity Silver Supporter

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    Great pic, Keith! That's a happy player, right there...

    B...b..but is that a BEER I see, perched on your baby? :eek: Looks pretty full, wish he'd take a sip already... :D

    Tell 'em we say hi...
     
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  11. brogh

    brogh Moderator Staff Member

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    Admin Post
    Indeed !
     
  12. Blue Bill

    Blue Bill Poster Extraordinaire Ad Free Member

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    That is awesome! A happy ending for all.
     
  13. CoyotesGator

    CoyotesGator Tele-Holic

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    A big smile, hot amps and cold beer!

    Well done sir, well done!
     
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