NAD: 1968 Super Reverb

[itsGiusto]

Nice amp and great price with the BF style cabinet!

Thanks!

Make it AB763 or keep it that way if it is. I wouldn't add the cathode caps on the power tubes.

Haha, definitely not adding caps, but I do find that having 1 ohm resistors on the cathodes really helps me to bias it. I don't like using things like the shunt method for biasing, I find it to be inaccurate, and potentially dangerous (but mostly inaccurate).

Does the baffle have the aluminum trim on it?

No, no drip edge, that was either removed when the grille cloth was replace, or it never existed. At some point today, I can put up a picture of the cab, it's kinda funny seeing it so different from the standard SR, but it's not trashy like some used amps I've gotten.

 

[D'tar]

may be adding big bottom to the sound, maybe too much in a 4 x 10 setup

Maybe have been addressed? Wonder what cap that is leading to the LTPI? It's not stock.

 

[itsGiusto]

Wonder what cap that is leading to the LTPI? It's not stock.

The yellow one? Yeah, I want to investigate that further, myself. Looks like a Mallory/mustard style thing you'd usually find in a Marshall (doesn't matter to me too much though). I think it says 0.001uf, though I gotta get out the magnifying glass on it tonight. I want to make sure it's the BF 0.001uf, not the later 0.01uf.

 

[schmee]

Thanks!

Haha, definitely not adding caps, but I do find that having 1 ohm resistors on the cathodes really helps me to bias it. I don't like using things like the shunt method for biasing, I find it to be inaccurate, and potentially dangerous (but mostly inaccurate).


No, no drip edge, that was either removed when the grille cloth was replace, or it never existed. At some point today, I can put up a picture of the cab, it's kinda funny seeing it so different from the standard SR, but it's not trashy like some used amps I've gotten.

They are just so great tone wise. None better. Wish I hadn't sold my perfect 66 several years ago. I have a cab and a tranny or two here, I may put together a "Super Rev-parts-verb" at some point... But trying to resist!

Get 'er tolexed and some good grill cloth for it!

 

[itsGiusto]

Looks like a good deal for 500. Main thing is if it works if transformers are good no shorts. Maybe you like the tone as is don't start changing things around to match some alleged vintage design on the internet. amps generate heat and the amp is 50+ yo so any crust and brown stuff doesn't mean tubes and stuff are messed up and have to get replaced right away. Seems your anticipating more of an electronics project. just enjoy how it sounds before messing with the components

I do come into these purchases assuming I'm getting myself into an electronics project. But when an amp is already to the specs I'd want to take it, then I'm fine leaving it as is.

 

[schmee]

The yellow one? Yeah, I want to investigate that further, myself. Looks like a Mallory/mustard style thing you'd usually find in a Marshall (doesn't matter to me too much though). I think it says 0.001uf, though I gotta get out the magnifying glass on it tonight. I want to make sure it's the BF 0.001uf, not the later 0.01uf.

That's appears to be a Mallory 150 replacement.
That PI cap is instrumental in the brightness and texture of these amps. Some of the Fenders use different values there. My Bandmaster Reverb was much improved by replacing that cap, it went from too bright all the time to much better.

The Supers can be a bit much/boomy on lower mids with the 4 x 10 configuration, especially with speaker upgrades. I wonder if they were trying to adjust that? Although .001 is stock on a Super I think.

 

[Derrick]

That’s 159 degrees F!? I think they are fine over in the preamp corner! Also, Don’t replace the tone circuit blue molded caps. That’s horrible advice. Leave them be. With that logic, might as well replace the OT, it’s probably at the end of its life

I second and third this... replacing the blue molded caps for absolutely no technical reason other than "the're old, so time to go" is stupid advice. I have found some from people who yanked them for this reason and put them in some old Fenders that had them yanked too and the amps all came alive! Orange drops are so sterile sounding to me. The Blue molded have a character that makes me want to keep playing, or turn the amp on when I'm not playing. They are not known to fail often either.

As for the transformer... that black drippy stuff is part of the manufacturing process. Typical and nothing to worry about.

Over all, you have an amp that doesn't need much electronically... more just cosmetics. You actually did quite amazing for $500! If no issues, then just check your tubes, check the bias, and decide if you want to reverse the master mod. Also get rid of the death cap. They move on to cosmetics and play that thing.

 

[Wally]

Nice amp. With the work that was done, it was a bargain, imho. @itsGiusto, the AC is not wired in the best and safest if I am seeing things correctly. The hot should go to the fuse then to the switch to connect to one end of the primary. The white neutral should go directly to the other end of the primary.

 

[Snfoilhat]

I couldn’t say how much difference orientation makes in a cab this tall, but i think it’s traditional for the reverb tank’s jacks to point toward the front, which puts the input/white on the left and the output/red on the right
Edit to add: when viewed from the rear

 

[Brian Krashpad]

pfft, once the reverb tank bag has gone theyre dead to me

worthless...

I'll be right over to buy up your worthless amps...

Then again, my '66 Super was cut in half decades ago (and has Sunn Magna 108s in it), so consider the source.

 

[SoK66]

Nice amp. With the work that was done, it was a bargain, imho. @itsGiusto, the AC is not wired in the best and safest if I am seeing things correctly. The hot should go to the fuse then to the switch to connect to one end of the primary. The white neutral should go directly to the other end of the primary.

Wally is absolutely correct re the A/C connections. Green to chassis ground, white directly to one of the two black primary PT leads, black to the center pole of the fuse, fuse holder side terminal to one pole of the power switch, the second black power transformer primary lead goes to the other pole of the power switch. Leave the ground switch completely out of the circuit. It and the death cap are the prehensile tails of antique electronics.

 

[Lowerleftcoast]

FYI the Blue Atom caps. Date codes:
0409H570, '04 - week 9.
0630H555, '06 - week 30.

A little older than you thought.

 

[SoK66]

I’m always amazed a how quickly people are ready to share the little information they have that is completely wrong in addition to perpetuating completely bogus information. I’m a USAF trained electronics tech who worked on military tube gear and later guitar amplifiers, specifically Fender, since 1989.

First off, nice score for $500! This looks to be a 68 AB763 as pointed out by some of the knowledgeable folks in this thread. Do not take the blue molded caps out and sell them on eBay. This is a transitional model still constructed almost entirely like the blackface amps. The brown cap in the middle of the amp circuit is what Fender would transition to later. This still has mostly Ajax blue molded caps - a really good thing because they sound great and are not as prone to leakage as the predecessor yellow Astrons. They sound better than the brown turd caps like the one in the middle of the circuit.

The solder joint with the 82k is in need of being re-flowed. It wouldn’t surprise me if you were able to tug on and pull out one of the components. It’s not a bad idea for reliability to reflow solder joints. Heat the components and the brass eyelet enough to melt the solder, don’t melt it on the iron. A little goes a long way.

The Blue Sprague Atoms are great. Leave them alone. Someone did a fine job there. They also did a fine job servicing the rest of the amp from what I can see. I can’t see the power cord, but the hot(black) should go to one of the transformer black wires, solder and heat shrink. The white should go to the fuse, other side of the fuse goes to the power switch, other side of the power switch goes to the other black transformer wire. This is the safest way to run it. Green goes to chassis like it already does. The death cap BS is an internet myth that has no basis in fact whatsoever. The ground switch and so -called death cap are abandoned with a 3 pronged cord. Do people REALLY think Leo put together these great sounding reliable amps with a cap that would kill you? And furthermore that Underwriter Laboratories put their stamp of approval on an amp that was defectively lethal and was inherently unsafe? Idiots. Please do not perpetuate the idiocy. That cap was designed to reduce hum. Shock hazards in vintage amps are a whole other subject I won’t go into, but that cap was not the cause.

If you want to do something, you can check the resistors for tolerance, which you should do with one leg out of circuit. This will also give you a good opportunity to retouch solder joints. Retention the tube sockets with a small screwdriver or a dental tool that has heat shrink on the knurled area for safety. Spray a little tuner cleaner in the pots if you have it. It’s the best stuff for cleaning pots, but extremely hard to find these days. Cramolin works too. Spend time turning them back and forth 20 or 30 times after spraying. Put some WD 40 on a q-tip and rub it on your tube pins then work the tubes in and out of their sockets several times to remove corrosion from where the tube pins contact the socket pins.
If you have a cap check machine like a Sencore LC75, which I use, or an ESR meter, check the caps Most, if not all, are likely to be within tolerance and free from leakage. Run the amp. There is a reason so many of the Fender amps are still around. They are reliable
and need very little to keep going. A servicing every 20 years, which this amp had recently, and tubes is all they need. Enjoy the amp. I’ve been looking for one of these myself. I’d have felt lucky to find what you found for the price you paid.

Why would you suggest it be wired with the hot lead (black) going directly to the PT then fusing and switching on the neutral (white)? That contradicts anything I've ever read because it puts unfused wall current into the PT full time and should the PT short to ground hot current goes directly to the chassis. Common practice is to wire white (neutral) directly to the PT primary then fuse and switch on hot. I'm not saying you are wrong, I'd just like to know your theory here as it's opposite anything I've read.

It's also common practice to eliminate the ground switch and "death cap" entirely, which you seem to advise otherwise. As I'm a veteran of the two-prong & death cap era, where getting a jolt from an ungrounded or revered polarity microphone or one of your bandmates was a rite of passage, I'm happy to eliminate the SoBs at the first opportunity. I recall vividly a spark about six inches long jumping from a Chicago Civic Opera house mic to my lower lip and blowing me off my feet, onto my keester and into the nether regions of consiousness for a few moment afterwards. I kinda like the three prong and no death cap world as a result.

 

[SoK66]

FYI the Blue Atom caps. Date codes:
0409H570, '04 - week 9.
0630H555, '06 - week 30.

A little older than you thought.

Thanks for clarification. Does that convention hold true for their smaller caps, like the 25/25 bypass and bias caps? I've been assuming that's the date code format but wasn't sure.

 

[Lowerleftcoast]

Does that convention hold true for their smaller caps, like the 25/25 bypass and bias caps?

I am no expert but I believe so, for the year span we are presented with here.

 

[Bluzzi]

Looks like a proper service to me.
The Spragues in the doghouse were part of it, as was the bias circuit which, for some reason, seems to get ignored.
Crabby old man comment of the day:
Everybody wants nice breakup at lower volume, but nobody wants the ceramic speakers that give it up.
The best-sounding SR I ever had was a drip-edge with Jensen ceramics.

Argh.....now you are reminding me of the one I let get away! Also a dripedge SR that sounded glorious (like my dripedge VR but louder!) and I quibbled about the price and it was a no so I left it. I regret it to this day. Best amp I ever heard after my 68 VR.

 

[sds1]

The doghouse seems to also have what I think are spragues, based on them saying "ATOM". Can anyone confirm? I'm pretty sure these aren't original at any rate, so it's unlikely I'd need to swap them out.

The Atoms are all over 15 years old, if it was my amp I'd just replace them while you have it open on the bench. Then you know it's been done and, barring any required service, can walk away from the amp for another 15-20 years.

 

[D'tar]

The Atoms are all over 15 years old, if it was my amp I'd just replace them while you have it open on the bench. Then you know it's been done and, barring any required service, can walk away from the amp for another 15-20 years.

I like this... do it now... bypass caps also! Dont forget bias cap! Anything else..... only if necessary!

 

[itsGiusto]

The Atoms are all over 15 years old, if it was my amp I'd just replace them while you have it open on the bench. Then you know it's been done and, barring any required service, can walk away from the amp for another 15-20 years.

I understand this and I partially agree, but I don't think I'm likely to go ahead and do it, mostly because I don't want to spend 30+ bucks on new capacitors. Those 500-600v caps are expensive! And then I'd have to wait around for them to arrive. Also it's not THAT hard to pop the chassis out to service when I need to do it in the future.

Also for the sake of argumentation and for my edification, is a cap's lifespan dependent on how long ago it was made, or how long ago it was installed? Or how long the amp has been left on? It's possible that the guy I bought from was telling the truth that the caps were installed only 10 years ago, maybe they were sitting around the tech's shop for a while. In that case, would the caps last longer?

 

[SoK66]

"Solid State, the sound of the future!"
View attachment 1071319

I understand this and I partially agree, but I don't think I'm likely to go ahead and do it, mostly because I don't want to spend 30+ bucks on new capacitors. Those 500-600v caps are expensive! And then I'd have to wait around for them to arrive. Also it's not THAT hard to pop the chassis out to service when I need to do it in the future.

Also for the sake of argumentation and for my edification, is a cap's lifespan dependent on how long ago it was made, or how long ago it was installed? Or how long the amp has been left on? It's possible that the guy I bought from was telling the truth that the caps were installed only 10 years ago, maybe they were sitting around the tech's shop for a while. In that case, would the caps last longer?

This is kind of a "how long is a piece of string" topic that kind of "depends". First is the quality of the caps, and the Spragues were considered very good at the time. OTOH, the IC caps Fender has used in virtually every tube amp since the 1980s are not well respected by amp techs and can fail very quickly in some amps. My own experience is that electrolytics last longer if the amp is used regularly. We see amps that are 30 years old running on the original Spragues. Last year I swapped out a set of them exactly like what you have that I'd installed in 2006, and all of them looked and measured just fine. Best practice is to source fresh electrolytics from suppliers as you need them. The chemical reactions inside them occur on the shelf as well as in an amp. Looking at your amp, I'd just run it and see how they fare. Filters will usually start making humming noises before they actually fail. If the amp is noisy it needs to be looked at by a tech and they can generally give you an idea of what's needed at the time they inspect it.