How to tell if '64 Deluxe Reverb is AA763 or AB763 Circuit?

[BassKulcha]

...without the tube chart (it's torn off at the top...)

No logo on grill cloth (though could be a re-cover)
Chassis stamp is A 01917
OPT code is 606419 (so, May '64)

Does the OPT date code automatically rule out the AA763 circuit? (I don't know when that change was instituted—)

I know one of the changes from the AA763 circuit was that the plate load resistors were changed...

"Fender went to an 82k plate load resistor presumably to balance the halves of the signal coming off the phase inverter. They also installed 1500 ohm resistors in series with the grids of the power tubes to dampen oscillation if there is any."​

AA763 schem of that area:

AB763 schem of that area:

 

[SapoAmpRepair]

AB763. You can see the 1.5k grid stoppers on your power tubes in the picture.

Nice amp!!

 

[Wally]

Those 1.5K ohm control grid stoppers are the ‘tell’. Both versions had the 470ohm screen grid stoppers.
BassK, the 1.5K control grid stoppers are the smaller 1/2 watt resistors placed between pins 1&5 on the 6V6s. The larger 470 ohm/1
Watt screen grid resistors are placed between pins 6&4. FYI, pins 1 & 6 are ‘blank’....there are no internal connections to those pins, and those pins are used as contact points for those resistors.

 

[BassKulcha]

Thanks, you guys rock!

 

[BassKulcha]

@Wally, I think I found the BFDR I’m going to swing for as opposed to the debacle with last “all-original” ‘67 with the replaced PT...

One issue that has me stumped however—the cab has corner protectors at the front bottom and back top (??)

Also, it’s so clean it makes me a little nervous, and I can’t tell if the Tolex and grill have been redone from the pics.

Could this entire cab be a replacement? Or did someone just put corner protectors on at some point? Everything else is looks beautiful and the resto work was apparently all done at Gruhn Guitars two years ago...

This ain’t cheap...(none are these days it seems), but this one sits in a good spot on the price continuum.
Only troubling issue is the corner protectors.

How “devalued” is this ‘64 BFDR now with that corner protector modification? Or since it’s not “all-original” now anyway, it’s not a big deal?

Thoughts anyone?

 

[Wally]

BassK, the grille cloth is obviously non-original. Not only that, but imho, the grille cloth needs to be redone...very sloppy work. The corners don’t belong there. I think there is a real possibility that the reverb driver transformer is non-original. It is hard to read, but I think that component is likely from 1973??? One would want all of the codes there. That is an Oxford speaker. There will be an EIA code on the frame of the speaker. That is an Oxford model number stamped on the back of the magnet, I think.
I want to see everything with a vintage Fender, so there are not enough good pics for me to think about value much. Tough call. If they are asking top dollar, they are asking too much, imho.

 

[BassKulcha]

BassK, the grille cloth is obviously non-original. Not only that, but imho, the grille cloth needs to be redone...very sloppy work. The corners don’t belong there. I think there is a real possibility that the reverb driver transformer is non-original. It is hard to read, but I think that component is likely from 1973??? One would want all of the codes there. That is an Oxford speaker. There will be an EIA code on the frame of the speaker. That is an Oxford model number stamped on the back of the magnet, I think.
I want to see everything with a vintage Fender, so there are not enough good pics for me to think about value much. Tough call. If they are asking top dollar, they are asking too much, imho.

Thanks for your input, Wally I appreciate it. Seller said all iron is original, so we’ll see. No chance that the entire cab was replaced right? (There’s no other cab that could fit a BFDR right—like a twin reverb etc—) so it’s just likely someone put the corners on at some point.

I see some seams in the 3/4 view Tolex images, not sure if that’s normal shrinkage or if it’s a sloppy recover..

Yeah I see the grill cloth is not perfectly squared up (at least on the top edge). Was hoping that maybe that was just slight buckling of the frame outward causing perspective wonkiness, but cloth is too clean to be original...

Seller said speaker is Oxford 12K5-6 “just professionally reconed”

It’s damn hard finding a good, honestly worked on vintage BFDR for not crazy money right now!

 

[Wally]

Check out the red marker/fingernail polish on the reverb driver screws. Someone placed those there to indicate that they had tightened them or as some attempt to prevent loosening...maybe it is red ‘Loctite’... and Fender did not do that. That drew my attention. Then, I THINK I see a model number that does not correspond to the year. Just as with the other DR you were looking at,
the 1964 codes start with 125..... As I said, it is impossible to say with 100% certainty what those numbers are because it is not the best picture, but I think I see 02 as the beginning of that number. The reverb driver does not affect my evaluation the way a PT or an OT replacement does, but if it is not original it is not original. Sometimes people know if it is not orig8nal, sometimes they don’t. I have to know based on what I see and not what they say.
Cloth...even if that cloth were applied properly and had been stained to replicate old cloth, the width of the wale gives it away. It is too wide in the measurement.

 

[Ten Over]

Like Wally said, 022921 reverb transformer numbers didn't appear until 1966.

The 1963/1964 reverb transformers that would have come with that amp had plastic wire. The earliest I have seen cloth wire is 1971.

The earliest I have seen "EIA" on a reverb transformer is 1977.

 

[BassKulcha]

Well, I have more pics...

Tube chart is stamped NG, so July 1964 date verified.

As @Ten Over wrote, the reverb TF code is EAI606--927 and has cloth wire, so is a later replacement (would that be 1969? '79?). That sucks...

Speaker is Oxford 12K5-6

Grill cloth is also redone, and not so well, as @Wally pointed out. Not for nothing, but the tolex is in rougher shape than anticipated— has obviously not been redone...

 

[Esquier]

Its knobs don't date from the '63-'66 period either. The correct early knob has its set screw going in from more underneath the 10-9 region instead of between 10 and 1. The early knob also sports the "snowman-like" number 8

 

[Esquier]

The first pic of your chassis looks like it's in gleaming nickel-plating. That's an early one like my '65. Mine just gleams especially the rear

 

[Wally]

The speaker is from early 1966....or maybe 1976?? At any rate, it is nor the original speaker even though it is the correct model of Oxford. With such a date code, it will be a low efficiency speaker. That change to low efficiency occurred in 1966.

 

[BassKulcha]

Its knobs don't date from the '63-'66 period either. The correct early knob has its set screw going in from more underneath the 10-9 region instead of between 10 and 1. The early knob also sports the "snowman-like" number 8

Good eyes!

The volume knob is definitely replaced, but all of the other knobs do have the "snowman" 8, as well as the set screw under the 10 (and some leaning towards the 9—the volume knob set screw, however, is definitely between the 10 and 1...)

 

[BassKulcha]

The speaker is from early 1966....or maybe 1976?? At any rate, it is nor the original speaker even though it is the correct model of Oxford. With such a date code, it will be a low efficiency speaker. That change to low efficiency occurred in 1966.

I'm assuming this means it doesn't get as loud? I'm working at bedroom volume levels so that's ok with me (unless, of course, the tone changes between hi-eff and low-eff speakers, more than the change between, say, Alnico and ceramic...)

in the HiFi world, you need high efficiency speakers (like my Altec Valencia 846A) with a low watt amp, such as a single-ended amp, either triode or pentode (lots of lower-end SE 6BQ5 stereo amps produced in the early-mid 60s...)

With two 6V6s running in push-pull getting 20+ Watts, I'm thinking that a lower-effiicency speaker is fine? (but, again, I'm still living in HiFi tube amp world and not guitar amp world...)

Man, so much to learn! But I really appreciate the experience and wisdom that you all bring...

 

[BassKulcha]

The first pic of your chassis looks like it's in gleaming nickel-plating. That's an early one like my '65. Mine just gleams especially the rear

I'm not experienced with being able to identify nickel plating vs zinc plating, but with a July '64 date code, that would probably be a pretty early example of nickel plating. I haven't found definitive dates on when that changeover occurred, but I guess I assumed it was with CBS in '65 (though even throughout '65 I'm sure that Fender was using up all the old parts—including chassis—that were manufactured under Leo's watch...)

More sleuthing required on my part, lol...

 

[clydethecat]

Its knobs don't date from the '63-'66 period either. The correct early knob has its set screw going in from more underneath the 10-9 region instead of between 10 and 1. The early knob also sports the "snowman-like" number 8

Looks like maybe just one replaced knob? The Vol doesn't match the other two.

Are those soldering iron burns in the tolex? Or cigarette...

 

[schmee]

Thanks for your input, Wally I appreciate it. Seller said all iron is original, so we’ll see. No chance that the entire cab was replaced right? (There’s no other cab that could fit a BFDR right—like a twin reverb etc—) so it’s just likely someone put the corners on at some point.

I see some seams in the 3/4 view Tolex images, not sure if that’s normal shrinkage or if it’s a sloppy recover..

Yeah I see the grill cloth is not perfectly squared up (at least on the top edge). Was hoping that maybe that was just slight buckling of the frame outward causing perspective wonkiness, but cloth is too clean to be original...

Seller said speaker is Oxford 12K5-6 “just professionally reconed”

It’s damn hard finding a good, honestly worked on vintage BFDR for not crazy money right now!

I don't think it's a replacement cab. The tolex looks "flat" and less nubby like that time period often was. It has that red mark on the baffle inside too. many of those older cabs have a number ink stamped inside the cab on the bottom under the reverb tank. The same number you see stamped inside the chassis to indicate year etc.
The grill cloth is replaced, but it appears they found some original style maybe the stuff Larry Rodgers used to have. Newer grill cloth is smaller rectangles. Keep that cloth but redo it.
The filter caps look big, I cant read the uf value but maybe they are higher value than 16-20?
The Oxford would usually have the Fender label on it, but I have seen plain labeled ones in the non reverb Deluxes.

 

[schmee]

For reference, I sold my 65 BFDR last year in one day on CL for $2400. I would say it was about as original generally and equal to this one but with much better condition tolex. Various things had been replaced as maintenance including many resistors and a couple of pots.

 

[BassKulcha]

For reference, I sold my 65 BFDR last year in one day on CL for $2400. I would say it was about as original generally and equal to this one but with much better condition tolex. Various things had been replaced as maintenance including many resistors and a couple of pots.

Thanks for the reference number. Prices for BFDRs have spiked over the last year, so $2400 would be a killer deal right now (which is probably why you sold yours in a day on CL—got another one? lol...)