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Nad! Pristine 1968 Drip Edge Super Reverb Ab763

Discussion in 'Glowing Bottle Tube Amp Forum' started by ShawnRocker, Mar 10, 2016.

  1. ShawnRocker

    ShawnRocker TDPRI Member

    39
    Dec 18, 2015
    San Francisco area
    I was just about to buy another SR when an out of state friend pointed me to a Craigslist ad in his area and I pounced. He did the transaction that day and shipped it, it arrived today.

    I don't think there could be a cleaner example out there. All original CTS speakers, even all original tubes including a few RCA 7025'sw and a smooth plate Telefunken. There are no dings or scratches of any kind in the tolex or in the shiny faceplate; not even the typical worm trails around the inputs. Has the original cover and the original foot-switch.

    I believe this amp has somewhere around 30 hours total playing time on it. I'll add the back story as I understand it at the bottom.

    I plugged it in once it arrived and there is a rattle somewhere in the speakers/cabinets I'll have to find; I plugged it into the chassis of a friends 67 Super that I recently repaired and it was still present and sounded the same. The guy who picked it up on the other end for me says he didn't notice a rattle so it's likely something that happened during shipping.

    It was quiet as a mouse initially, but developed a significant hum after about 30 minutes of playing with the Vol around 3; probably the 1st workout it received in 30 or 40 years. Rather than risk damage, i turned it off and readied it for a cap job; I think I'll install F&T's.

    The original foot- switch wouldn't turn the Vibrato on but a reissue switch did, I'll troubleshoot that. However the Vibrato was pretty weak once it did get on, even with the Intensity at 10; Nowhere near as sublime sounding as that in the 67.

    It was brighter sounding than the Jensen equip'd 67 sitting next to it.

    So I pull the chassis and see it's from the 6th week of 1968, 3 weeks after the Princeton Reverb I recently posted about and received a ton of great advice that helped me get dialed in and sounding fantastic. I also have 1st dibs on a excellent Bandmaster from the 5th week of that year I may have to take just build a collection of early '68, AB763 Drip Edge's.

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    Back story: The guy I communicated with about the amp said it belonged to a lady from his church who needed to get rid of it as she prepares to move into an assisted living home. She bought it for her son new, but he gave up learning guitar after a few lessons and she put the cover on it ans stuck it in a closet. Occasionally her husband would pull it out and tinker, but he wasn't really a player and he passed years ago. She approached the guy I communicated to at church because he's in the band. He said he didn't have use for it since he only plays bass but offered to help her find a value and sell it. She was hoping to get a few hundred for it and was elated with my offer of $1,100 which was made before I understood how mint this one was; I only new it was cleaner than the local one I was about to buy for $1,200 and figured the $100 would equal out on shipping.
     
    wmsimpson and Fret Wilkes like this.

  2. Ricky D.

    Ricky D. Poster Extraordinaire

    Age:
    66
    Oct 22, 2006
    Garner, North Carolina
    Wow. Just wow. Nice one.

    Gotta play it. Out. With other players, nice big room so you can crank it. It will be beautiful.
     

  3. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Bargain time there, indeed. They don't come that clean very often.
     

  4. BobbyZ

    BobbyZ Doctor of Teleocity

    Jan 12, 2011
    Snellman MN
    I've had a few Grain Belts but that looks like a blackface circuit !
    She'll be a sweet amp once you change all the electrolytics and install a grounded cord. Unless you like the occasional shock. :)
     

  5. ShawnRocker

    ShawnRocker TDPRI Member

    39
    Dec 18, 2015
    San Francisco area
    Oh I will. Looking forward to it.
    I still owe you a big thank you from your advice on the Princeton. I learned a ton from that experience and even more as I repaired my friends 67 SR.
    It already gave me a shock. Owner of the 67 came over to hear the 68. Like I said the footswitch wouldn't turn on the vibrato so I plugged that one's switch in to the 68, but the switch was still sitting on the 67's cab. As we were playing music I reached over to flip on something and, with my right hand on my guitar, my left hand touched the handle metal on his and I got bit. No fun!
     

  6. Chris S.

    Chris S. Asst. Admin Staff Member

    Age:
    114
    Mar 26, 2005
    Near TELE-Town (Wash. DC)
    Admin Post
    Man, that is CLEAN. Congratulations on a great score. And I bet it'll sound just as good as it looks. I love Super Reverbs, always have. CS
     

  7. sbpark

    sbpark Friend of Leo's

    Feb 10, 2009
    The West

  8. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    Very sweet, congrats.
     

  9. DannyJustQuit

    DannyJustQuit Tele-Meister

    117
    Oct 28, 2015
    Massachussetts
    Awesome man, that is friggin' awesome!
     

  10. electroman

    electroman TDPRI Member

    44
    Nov 1, 2012
    Hamilton, Ontario
    Congrats; that is a beautiful amp. How do you know the electrolytics need changing? I still have the original caps in my 1966 Tremolux and they are close to original spec. My amp tech told me not to change them. I'm sure your tech will advise and also find the hum source. I'm not a tech but from my experience the hum that starts after the amp has been on for a few minutes and gets louder is caused by a bad power tube or a bad bias capacitor. Good luck and it's great that it will be ship shape once again.
     

  11. keithb7

    keithb7 Friend of Leo's

    Age:
    46
    Jan 9, 2010
    Western Canada
    Nice amp. Great find. Yup cap job and a 3 prong cord. I bet that vibrato needs a cathode by-pass cap or resistor replaced.
    She's a beauty. Play it out and give it the life it always wanted.

    Since someone asked about electrolytic caps here's the scoop below. If one fails and takes out your power transformer it's gone for good. Not worth the risk to me. I recap 'em.

    The weakest link in power supply is usually one of the electrolytic capacitors. Usually electronics repair people need to replace more electrolytic capacitors than any other electronic components in electronic repair. The aluminum electrolytic capacitor has a limited life span. This occurs because the electrolyte in the element eventually dissipates. Since electrolytic capacitors are not hermetically sealed, the electrolyte in these capacitor eventually evaporates causing increased ESR which causes increased heating, which causes the safety seal on the capacitor to pop, because if it does not pop, the capacitor explodes. Once these capacitors fail, they can cause all kinds of secondary failures. Why this kind of often failing components are then used? By combining small size and very low cost per unit capacitance, electrolytic capacitors are the only cost-effective choice for high-value applications like power supply filtering in most consumer gear.
    The changes in performance over time can be described as follows: Eventually, the capacitance begins to drop off and internal resistance (ESR) starts to increase. The loss in capacitor begins to increase, causing it to heat up more and go bad more quickly. Finally, at the end of the life span, the capacitor enters an open circuit mode as the dielectric dries up.
     

  12. newrider1969

    newrider1969 Tele-Meister

    Age:
    48
    481
    Feb 11, 2005
    st david il
    Beautiful amp and Kudos for making a reasonable offer to the woman.
     

  13. BobbyZ

    BobbyZ Doctor of Teleocity

    Jan 12, 2011
    Snellman MN
    Old electrolytics can seem fine, no hums or any of the "classic" signs of failure. But still be weak and cause the low end to get loose and farty.
    The "fix" is a new speaker.(s) Normally a new speaker is more efficient (louder) and in alot of cases it's enough to mask the real problem because the amp doesn't get pushed as hard.

    The only accurate test is subbing in fresh caps, the second best is pulling them and testing them in a tester that checks them at their rated voltage. (Very few people have one of those) In both cases the untouched solder joints get touched.
    At that point. What's the point in keeping them?


    Think about a set of original tires on a 500 mile 65 Corvette. They're round, black, hold air, you open it up and the don't blow on a five mile drive. They test fine!
    Would you drive it across country?

    Anyway if you want to run old Ecaps go ahead, it's you're amp.
     
    Last edited: Mar 12, 2016

  14. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Ime, old caps will exhibit loose low end with out of tune sub harmonics, lack of sparkle on the high end, and a flat sound stage. Fresh caps will yield a firm in tune low end, sparkle on the high end, and a 3-dimensional soundstage. It is revealing to amp owners who thought their 1968 Fender sounded great to hear it with fresh electrolytics and good service.....it will be a different amp and much more like it was when it was new. Their eyes go wide....
    For me, the analogy in the car world would be old spark plugs and ignition components versus new ones. The engine might run with the old parts, but it will be much stronger with a proper tune up.
     

  15. jazzguitar

    jazzguitar Tele-Afflicted

    Mar 17, 2003
    Germany
    Beautiful amp!

    Inevitably someone will post the usual "replace-all-electrolytic-capacitors".

    I agree that the high voltage caps are probably wise to be replaced for safety, as you plan to do (if it were mine I would keep the others, in particular if it sounds good. It is revealing if you install all new bypass caps and the sound does not change any as the old ones are still good)

    Hum after some time on can be a heat related problem, eg a hot component stops working well, or some contact gets bad, hard to track down with open chassis as this way the part will never get as hot.

    First try different vibrato tubes in V5 slot, sometimes it is just that; the vibrato circuit is a design somewhat operating on the fringe and sometimes even good tubes provide less than optimum result. Sometimes the neon bulb got dark but surely not in this case, and sometimes the LDR gets weak as it ages.

    Rattling often is hard to find, but you can try the speakers one by one (or disconnect one every round). Maybe it's just some minor part or dust fell into the speaker basket. I do not really believe any one of the four is bad when they have seen so little use!
     

  16. telex76

    telex76 Doctor of Teleocity Ad Free Member

    Age:
    66
    Jun 24, 2006
    Fort Worth,Tx.
    Old electrolytic caps that have been played regularly would have a much better chance at still being good than caps that have sat unplayed.
     

  17. BobbyZ

    BobbyZ Doctor of Teleocity

    Jan 12, 2011
    Snellman MN
    Those late blackface early silverface bypass caps are garbage. The big paper roll ones used untill 65 or 66 held up better. Although I still replace all of those too.
    There was no electrolytic caps used on a silverface that are worth messing with.



    But if anybody wants to buy some to put back in let me know.
    Maybe I should Ebay them ? :)
     

  18. charlie chitlin

    charlie chitlin Doctor of Teleocity Ad Free Member

    Age:
    55
    Mar 17, 2003
    Spring City, Pa
    I had 2 SRs at once awhile ago.
    A '66 and a '68.
    The '66 sounds great (still have it), but the '68 had that SR THING in spades!!!
    Killer!!
    I sold the '68 and kept the blackface because...well...blackface; and I'll likely sell it someday.
    If it was tone alone, I'd have kept the silver one.
     

  19. jcss

    jcss TDPRI Member

    84
    Feb 6, 2013
    midwest
    If this were a sort of rough amp, i might take a chance on the stock electrolytics....in this case I would replace the electrolytics imo.

    On the CTS alnicos, many times the doping on the speaker surround will harden....hopefully yours have not... even though the speakers still put out sound, the voice coil will not move in & out.
     

  20. ShawnRocker

    ShawnRocker TDPRI Member

    39
    Dec 18, 2015
    San Francisco area
    Thanks for all the feedback and advice. I'm going to replace the electrolytics. There's more to lose by not doing it than there is to gain by leaving them alone.

    While I wait for the caps to arrive, and a couple other projects I have going, I am lucky to have the friends 67 SR to help me track down the rattle in the 68's cabinet. How's this for a look? Personally I think they look great together.

    [​IMG]
     

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