NAD...1966 Fender Pro Reverb. Circuit Questions

ashtone54

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Wally, Weber also suggests swapping the output transformer with one from a BF Bassman. Have you, or anyone, tried it?

Here’s before and after grille cleaning shots. Some like the funky look, not me I like the "after" look. That’s up to you.
I used a vacuum to get the loose stuff first. Amazing how much crap gets in the backside of a baffle! Sprayed some 409, simple green should be ok, brushed it and rinsed it with a hose. I didn’t go crazy with the hose just enough to fully rinse it. Then let it dry in the sun.

With only a few exceptions Amps are what I regret selling. This is one in the regret file! Recently I found out a tech pal used to own one of Gatton's VR and had recorded all the circuit mods!

FWIW, this amp had no Tube Chart and no evidence it ever had one. 64 parts, Jan 65 Oxfords.

View attachment 979813
17E2BD31-7D41-4A75-90DB-9FDABCF92B4B.jpeg

You have a keeper! Here’s mine.
 

Wally

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About two months ago I picked up a mostly stock '66 Pro Reverb that had been rehoused in a head cabinet. Lots of people online love the Eminence GA-SC64 12" speakers because they're close the original sound of the amp, so I ordered two of them. Put them in a 2x12 cab, and they do sound great. I can't compare them to anything else though, so my perspective is limited.

I've since added a negative feedback control pot (in place of the ext speaker jack) and a mids control pot (in place of the courtesy AC outlet). Both are easily reversible mods in case I want to return it to stock. These mods both help bring out the mid-range in the amp in different ways. But I suppose selecting more mids-forward speakers might have achieved the same thing.

In any case, it's a wonderful amp. Have fun!

Jason

Jason, ime, selecting a more mid forwards speaker does not achieve the same thing as does bumping up the midrange. A speaker can change the character of the tone, but a midrange bump can be a real gain changer in the preamp. This can make for a hotter amp….no matter what speaker one uses.
 

fushifushi

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Jason, ime, selecting a more mid forwards speaker does not achieve the same thing as does bumping up the midrange. A speaker can change the character of the tone, but a midrange bump can be a real gain changer in the preamp. This can make for a hotter amp….no matter what speaker one uses.

Thanks for making this point. Very true. Both the mids control and NFB control can boost the gain in the preamp. They also have nuanced effects on the treble and bass response. So yeah, swapping in mids-forward speakers might be able to bring out more mids as a one-shot deal, but they wouldn't be as flexible and dynamic as these controls.
 

Lorestone

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If you're going to remove the baffle and clean the grillcloth I recommend that you remove the logo. The black paint on the chrome is very delicate, is not well adhered to the chrome, and will chip off if you even lightly scrub it. As far as cleaning the grill cloth - I have done so using Fantastik. I lightly soaked it with the spray, then sponged it off with a sponge in the shower/tub. Then I did a number of rinses with the wet sponge, angling the face of the grill down so the water runs away from the baffle. You want to keep the water off the particle board as much as possible. With a plywood baffle I've done the same with the Fantastik but rinsed off the cloth in the shower with a handheld shower head, angling the face of the grill downward, with the water hitting the grill at an acute angle so the water is rinsing the cloth and running off immediately as you're doing it. Plywood can withstand water better than the chipboard.
 
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Taley67

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Hi
I m a common user of neodyme speakers
Have you think about :
Jensen Jet Tornado neo ?
Célestion Neo ?
Celestion Century Vintage neo ?
Those are well matched with my Fender the twin (dual shomann cousin)
 

76standard

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View attachment 978184
Got a new amp today! 1966 Fender Pro Reverb. Transformer date codes check out. Has replacement Jensen C12Q speakers, 3 prong grounding, and a cap job...but otherwise is original. I'm going to clean up the grill cloth and tolex with some Spray-Nine and let air dry. Since the speakers were replaced already...seriously considering a pair of Celestion NEO v-Types in here to keep the weight down and give it more of a midrange bark.

Speaking of midrange...I had a question about the circuit. It's supposed to be the AA165. I thought this circuit was a brief precursor to the Bassman AB165? It's a bit of an odd duck and the only other Fender blackface amp I can think of that has this AA165 circuit. I'd love some information on this circuit from the forum.
The AA165 circuit is a keeper. I wouldn't change a thing other than have the caps checked for any possible leakage. An amp that old should be gone thru by a qualified tech. Have you tech verify the circuit when they look under the hood. Keep in mind that the AB668 circuit was also installed into some Pro Reverbs built in 1966. I own a 1974 Pro Reverb. It's the silverface version with a master volume control that either had the AB668 circuit. I had my amp tech convert the circuit to AA165.

Here is a really good link to a website (Fender Guru) that will provide a wealth of knowledge about Fender amps. In yours and my case the Pro Reverb. I highly recommend reading this information to better understand your amp and its capabilities. Since you are considering a speaker replacement, scroll down to the section about speakers. There is link to a page describing various speakers you might want to consider. The "holy grail" of speakers put in these amps back in the day was the Jensen C12N. Good luck trying to find a nice pair of those.

Just a bit more about speakers. You could sell the Jensens to underwrite the cost of a good pair of new speakers. I would stick to speakers that are more true to the Fender sound if that is one of your goals. I understand your desire to reduce the weight of the amp. Here is the dilemma, most of these old amps had AlNiCo magnets in the speakers, thus the C12N. I'm sure if your goal is to replicate that vintage Fender blackface tone consider speakers that are described more along those lines. I put Weber 12A150 speakers in my amp and couldn't be happier. They hold together nicely with my clean tone, and when the amp is pushed they have a nice smooth breakup with a bit of compression. Weber does a good job describing the tonal voice of their various speakers. Likewise, Eminence and Warehouse Guitar Speakers also have some good descriptions of their speakers. Speakers are a very personal choice so I will leave this topic up to you. Here's are three good links about speakers.

Weber 12" Vintage Speakers
Eminence Guitar Speakers
Warehouse Guitar Speakers
 

Wally

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Keep in mind that the AB668 circuit was also installed into some Pro Reverbs built in 1966. I own a 1974 Pro Reverb. It's the silverface version with a master volume control that either had the AB668 circuit.

Fender schematics had a date code for the date drawn. The first Pro Reverb schematic was drawin January, 1965….AA165. The second was the June, 1968 schematic…AB668. fowllowing that 1968 circuit, there was AA1069…Oct, 1979 and AA270….Feb,1980. The MV circuit was drawn in 1974. construction any of these circuits did not take place before the schematic was drawn…unless it was a special prototype. A prototype could possibly predate a formal schematic date code????
However, there was no AB668 circuit built in 1966 or 1974. You might find an AB668 tube chart in a 1979 or even 1970 amp, but the circuit will be the later circuit...’69 or 1970.
 

KeepItSimpleTele

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Ran into some issues when I got the baffle board off for grill cloth cleaning. The particle board baffle is in rough shape. I now know why there was those two screws through the front (to attached the speaker baffle which was falling apart to the cab!).

I thought it best to just get a new baffle board. I got a vintage replica one with vintage correct aged grill cloth coming in the mail. It must have been fate to see it posted on Reverb for cheap nearby! I think I’ll just transfer over the original logo…but is there really any reason to keep the old grill cloth in this case? Baffle board is trash for sure.
 

AlbertaGriff

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Ran into some issues when I got the baffle board off for grill cloth cleaning. The particle board baffle is in rough shape. I now know why there was those two screws through the front (to attached the speaker baffle which was falling apart to the cab!).

I thought it best to just get a new baffle board. I got a vintage replica one with vintage correct aged grill cloth coming in the mail. It must have been fate to see it posted on Reverb for cheap nearby! I think I’ll just transfer over the original logo…but is there really any reason to keep the old grill cloth in this case? Baffle board is trash for sure.
I would keep every original part.
 

Wally

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However, there was no AB668 circuit built in 1966 or 1974. You might find an AB668 tube chart in a 1979 or even 1970 amp, but the circuit will be the later circuit...’69 or 1970.

Okay, this should read “You might find an AB868 tube chart in a 1969…..”…..1969 instead of 1979. Apologies.
 

KeepItSimpleTele

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I would Repair the original baffleboard.
Is ‘t it a bit like trying to retread a tire from 1966? Perhaps the baffle has done its time vibrating away and should be recycled :)

Seriously though…it’s got chunks missing and is falling apart at the bottom. I may be able to clean and put the original grill cloth away for safekeeping though
 

Wally

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Is ‘t it a bit like trying to retread a tire from 1966? Perhaps the baffle has done its time vibrating away and should be recycled :)

Seriously though…it’s got chunks missing and is falling apart at the bottom. I may be able to clean and put the original grill cloth away for safekeeping though

Okay….Falling apart at the bottom. That is explained by the stain on that grille cloth that indicated some possibly serious water exposure. Understood.
I would buy/build a new plywood board and apply that original grille cloth to it. Or…if the board you bought is a good plywood board, pull that cloth and apply the original cloth to that board. Take a picture of the original board before you toss it. Keep the picture for the amp’s historical record…in this case explaining why the board was replaced and also establishing the originality of this cloth to this amp. Yessir, that is how I am. Old school I am when it comes to originality. If that cloth has always been on the amp, the value of the amp is better maintained than if there is new cloth on the replacement board. The tears in the original cloth in the before and after cleaning should be kept with the amp, too, imho. These are what establish the originality of the cloth.
 

InstantCoffeeBlue

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Ran into some issues when I got the baffle board off for grill cloth cleaning. The particle board baffle is in rough shape. I now know why there was those two screws through the front (to attached the speaker baffle which was falling apart to the cab!).

I thought it best to just get a new baffle board. I got a vintage replica one with vintage correct aged grill cloth coming in the mail. It must have been fate to see it posted on Reverb for cheap nearby! I think I’ll just transfer over the original logo…but is there really any reason to keep the old grill cloth in this case? Baffle board is trash for sure.

I had a similar issue with my Princeton and had Mojotone build me a new grille frame to replace the crumbling particle board that was warped to the point it wouldn't sit flush in the cab. It's nice, but even their "aged" cloth looks shiny and new and lacks the character of the original. As silly as it may sound to some, I've been thinking of sending them the original board w/grille cloth and having them build another frame with the old, torn, nicotine-soaked cloth.🤷🏻‍♂️
 

KeepItSimpleTele

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Okay….Falling apart at the bottom. That is explained by the stain on that grille cloth that indicated some possibly serious water exposure. Understood.
I would buy/build a new plywood board and apply that original grille cloth to it. Or…if the board you bought is a good plywood board, pull that cloth and apply the original cloth to that board. Take a picture of the original board before you toss it. Keep the picture for the amp’s historical record…in this case explaining why the board was replaced and also establishing the originality of this cloth to this amp. Yessir, that is how I am. Old school I am when it comes to originality. If that cloth has always been on the amp, the value of the amp is better maintained than if there is new cloth on the replacement board. The tears in the original cloth in the before and after cleaning should be kept with the amp, too, imho. These are what establish the originality of the cloth.
I like your style. I’ll clean the old cloth gently…I’m hoping the screws piercing the bottom of the cloth that were holding on the old baffle didn’t cause too much damage (previous owner). I like character in an old grill cloth… but I draw the line at a certain point ;) Lots of pics documenting is a great idea.

I’ll get some after pics up once the new baffle arrives.
 

Wally

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I’m hoping the screws piercing the bottom of the cloth that were holding on the old baffle didn’t cause too much damage (previous owner)
Okay, I straightened me out. I was functioning under the understanding that you had already cleaned the cloth, but I see now that another member posted pics of their results with cleaning. I saw your cloth, and it should be preferable to new cloth…for my purposes and as long as the regrilling is done well.
 
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