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Restoring an old Twin reverb

Discussion in 'Amp Tech Center' started by Blue Bill, Oct 25, 2020.

  1. Blue Bill

    Blue Bill Poster Extraordinaire Ad Free Member

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    TenOver and Wildman are making me think I should just clean it off and plug it in. I've heard many warnings about old caps failing catastrophically and wrecking everything. Should I rig up one of those light-bulb protection test-rigs? I think I have one kicking around from years ago.

    I'll bet that if I spend the time and money to bring it to gigging condition, I'll never sell it. That wouldn't really suck, though, would it?

    Indecision sucks.
     
  2. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    Do not turn the amp *on* in it's current condition. A cap may blow taking out other parts of the amp with it. If you will be selling the amp without changing anything, I would suggest you re-form the caps. Once the caps have been re-formed, the amp might be able to be demonstrated to show the prospective buyer that it functions.
     
    Last edited: Oct 26, 2020
  3. Ten Over

    Ten Over Tele-Holic

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    I didn't say anything about plugging it in.
     
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  4. Blue Bill

    Blue Bill Poster Extraordinaire Ad Free Member

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    More Pictures: The reverb transformer wires look kinda new compared with everything else.

    123_0441.JPG 123_0453.JPG 123_0498.JPG 123_0446.JPG
     
  5. Milspec

    Milspec Poster Extraordinaire Silver Supporter

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    Depending on your final intentions for this amp, I strongly suggest 2 other things not mentioned.

    1. Replace the rectifier diodes. They seem to be a real weak spot on Fender Twins and I have even found some that left the factory with specs not matching the schematic like they just grabbed what they had and decided "close enough".
    2. Put some NOS Jan-Phillips 12AT7 in those 2 slots. I have never found any modern AT7 tube sound near as lively.
     
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  6. Blue Bill

    Blue Bill Poster Extraordinaire Ad Free Member

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    Hi Milspec, Not a bad idea, replacing the rectifier components. I'll also look around for those tubes. My final intentions appear to be equivocal at the moment; it's after midnight and I need to sleep on it. Thanks guys!
     
  7. 24 track

    24 track Doctor of Teleocity Silver Supporter

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    if you recap it then its been altered , a collector may want it stock untouched

    Jmho if you recap the unit , use high quality caps like F&T's made in germany ( the best I have found so far ) save all the old caps and sell them with the unit for authenticity,

    contact Fenderjunkie and get the full kit , I use him exclusively ( check out his store ) or contact him directly , not only does he have the full kit but also a full set of instructions to do the repair. he will have or make the kit up for you .

    https://www.ebay.ca/itm/RECAP-KIT-for-Fender-Super-Pro-Bandmaster-Reverb-amp/190495801799?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

    think of it this way , would you want a fully running 65'mustang fastback or one that needs a new engine? plus you get the original parts in the deal
     
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  8. Ten Over

    Ten Over Tele-Holic

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    Well then, turn it over and post some pictures of the transformers.
     
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  9. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

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    They were stock. Same caps were in my '67 Super Reverb.
     
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  10. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

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    I don't understand why you would suggest those caps are not stock. I have seen them in a few amps from that era. And, it would make zero since at all to leave the two series main filter and replace the others. So, I believe you are wrong.

    The amp probably had an output tube failure which burned up a screen resistor. The tech just replaced the screen resistors and left most everything else stock because it was working.
     
    Last edited: Oct 26, 2020
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  11. Wally

    Wally Telefied Ad Free Member

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    The tube chart date stands....the amp is from 1966 and was built with a chassis that was stamped in 1965. If the amp is to be sold, sell it as is. For my money, I would rather buy the amp as it is. If you want to assure a buyer that it works, the amp needs to be brought up on a Variac over a considerable period of time in stages...20 volts, 30 volts, 40 volts, etc.....all day type of thing to reach 117VAC. 15 years with no current is a long time for those electrolytics, imho.
    Pics of the transformer codes would help ascertain their originality. That originality and value has been hurt with those modern Jensens. If I were buying the amp, the seller could keep those speakers.
     
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  12. Wally

    Wally Telefied Ad Free Member

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    That kit is not complete in that there is no bias capacitor there. If he is intending one of those 52vdc/25mfd e-caps for the bias, one should beware. There should be 7 of those 25/25 caps and a larger cap for the bias circuit.
     
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  13. Blue Bill

    Blue Bill Poster Extraordinaire Ad Free Member

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    Hi Wally, that's what I think makes sense, it's a '66, with a '65 chassis. Maybe a sensible plan would be to clean it up and put it back together, then bring it to a shop to reform the caps with a Variac. I realize the speakers have negative value for a vintage piece, when I got the amp, one of the originals was already replaced.

    The PT is stamped: 622 756 606 616 SSA TEST
    123_0481.JPG

    The reverb transformer numbers are: 022699 606-6-09
    123_0483.JPG

    Should I worry about a bit of leakage from the top of the PT?
    123_0452.JPG
     
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  14. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

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    The solder terminals on the transformer studs suggest it is at least a '66.

    Edit: I'm not 100% on exactly what point and which amps they made that transition. I've seen it on every '67, and never on a '65.
     
    Last edited: Oct 26, 2020
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  15. Engine Swap

    Engine Swap Tele-Holic

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    Date codes say 1964 - where are you getting 1970/71?
     
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  16. Wally

    Wally Telefied Ad Free Member

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    BlueBill, ime, there is nothing to worry about except firing the amp up as it is. I know what I would do....I would replace all electrolytics, do good general service, clean the amp as part of that service, and see what is there. My advice to sell it as is was for a person who is asking what to do rather than for someone who is unsure. That lack of assurance to what to do is why I said sell it as is.
    Imho, that amp needs to be brought back to life by an experienced tech. Ommv.....but I do not consider such an amp to be a good learning platform. That stain on the PT indicates some heat in the tranny at some time....and maybe that is related to the screen grid resistors’ replacement?? Who knows? After a recap and proper service, one then finds out what shape the transformers are in. Sometimes one finds a problem in a transformer at that point, but most of the time the trannies are good. If that amp came to me as it is and was for sale, I have bargaining chips because of the details in this amp. More than likely, though, there is a great amp waiting to be brought back to life. One has to be aware that there is the possibility of a major problem, though.
     
  17. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

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    I don't even see what looks like a possible code with a date except the very last preamp filter cap, because it's sitting at a different angle, and it's too blurry in the photo to make out completely.

    The solder joints are obviously undisturbed and original, so it's kind of a moot point.
     
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  18. Blue Bill

    Blue Bill Poster Extraordinaire Ad Free Member

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    Yeah, Wally, you are correct about the lack of assurance. The reason I've never sold it is, it's such a great sounding amp. In my 20s, I didn't mind lugging it around. I even had another Twin back then, with 2 EVM12Ls, it must have weighed 100 pounds. Nowadays, it seems so big, heavy and loud, yet the thought of selling it makes me sad. :cry: I have a bit of tech experience, although it's been a while. I so much appreciate he generosity of the people here on TDPRI, who have more expertise than I.

    Right now, I'm leaning toward what you and 24 Track are suggesting; go ahead with the e-cap replacement, find a Variac, and see how it goes.

    amprepairparts.com is offering a re-cap kit for $67, that looks about identical to the one Fenderjunkie has listed for $89. Hmmm. I have set aside a few hundred for this project, so I don't really need to nickle-dime, but I'm also a chronic cheap-skate.
     
  19. Engine Swap

    Engine Swap Tele-Holic

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    All those parts can be bought at Mouser, Digikey, etc... for around $20-25.

    Would leave the amp alone if you want to sell it soon.
     
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  20. Blue Bill

    Blue Bill Poster Extraordinaire Ad Free Member

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    I'm fairly confident that the amp was produced in mid-'66, which is a transitional time for Fender. So far, it appears to have none of the drawbacks of the evil-CBS phase.

    I didn't try to spin the filter caps to photo the numbers. If they are fragile, I don't want to damage anything.

    I gotta go to work, see y'all later!

    OT #s: 022889 8316605
     
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