1968 Super Reverb - AB763 circuit??

[AlRob]

Hi,
I'm considering a purchase of a 1968 Fender Super Reverb (silverface drip-edge)
Im pretty sure it's a 1968 (SN: A33959) From what I've read this was a transition year for the circuitry in this amp.
The tube chart inside the amp says its a AB763 circuit and the owner says it is, but he hasn't or won't give me his reason for absolutely believing it is AB763. I've heard the tube charts were not always accurate stating the circuit during this period.
He sent me some gut shot photos but because of the angle of these photos i find it difficult to really compare to photos/blueprints. I am a novice at this.
Can anyone help tell if this is an AB763? I surely appreciate your help.

http://www.docksidemusic.com/images/SR1.JPG


http://www.docksidemusic.com/images/SR2.JPG

[Blue Strat]

It's difficult to see details, but the 2 resistors coming off the bias pot say it's a later circuit.

[jitterbug]

Tell him you want a better picture of that board because from what I see in the pic the phase inverter and bias supply sections look more like an ab568 circuit. Those plate resistors look to be 47K and like Blue Strat mentioned those two resistors from the bias pot

[Blue Strat]

Tell him you want a better picture of that board because from what I see in the pic the phase inverter and bias supply sections look more like an ab568 circuit. Those plate resistors look to be 47K and like Blue Strat mentioned those two resistors from the bias pot


Good eyes! No way this is a 763.

[AlRob]

Yeah its looking like this might be AB568. I've looked at some AB763 photos and I dont see those resistors on the bias pot. Are these easily blackfaced? Thanks guys

[Blue Strat]

Yeah its looking like this might be AB568. I've looked at some AB763 photos and I dont see those resistors on the bias pot. Are these easily blackfaced? Thanks guys

Yes, easily blackfaced except for the 5U4>>5AR4 conversion (for FULL blackface) which almost no one does.

[TweeDLX]

Just to toss in my $.02, I actually prefer the SF PI to the BF, but it really depends on the tone you want from the amp. I'd definitely change that balance pot to a standard bias adjust (or add a bias adjust and keep the balance, too) for convenience sake. If the price is right, snap it up.

[AlRob]

Sellers asking for $1200 as a AB763. Being this is actually a AB568, is this still a good price?

[deeval]

No you should tell him you will offer 900.00,and does it have the CTS speakers?

[wizard333]

Very cheap to make it AB763, if thats what you want. Have you actually heard it side by side to be sure thats what you want, or is that based on internet hype over the AB763 circuit?

A lot of people pay me to BF a SF, and I always tell them, there is nothing wrong with the SF depending on what you want to do with it, listen first. Few do.

[AlRob]

Very cheap to make it AB763, if thats what you want. Have you actually heard it side by side to be sure thats what you want, or is that based on internet hype over the AB763 circuit?

A lot of people pay me to BF a SF, and I always tell them, there is nothing wrong with the SF depending on what you want to do with it, listen first. Few do.

Internet hype says the blackface AB763 is the desired and from more than a few posts I've read, AB568 is often classified as "dreaded"
Unfortunately since I am buying online I cannot listen to the amp.

[AlRob]

No you should tell him you will offer 900.00,and does it have the CTS speakers?

Yes I believe has the CTS speakers. The ones with the boxy looking thing on the back of the speaker.

[wizard333]

I laugh when I see any vintage fender circuit described as Dreaded. The most Dreaded of them all are the ultra linear late 70s ones, but I'll tell you what, I've worked on a lot of them and they can sound fantastic.

My advice is see if you can get a good price regardless, then if you dont like it, you can have the circuit changed very cheaply.

[deeval]

Very cheap to make it AB763, if thats what you want. Have you actually heard it side by side to be sure thats what you want, or is that based on internet hype over the AB763 circuit?

A lot of people pay me to BF a SF, and I always tell them, there is nothing wrong with the SF depending on what you want to do with it, listen first. Few do.

Thats correct, but he cant try side X side,so 900.00 is a fair price which is what was asked,and yes I have had 68 SF SR,s that sounded as good as a BF but they had the AB763 circuit.

[SamBooka]

I have one.. look at the big funky cathode resistors on the power tubes. I am not a fan of BFing something up just for BFing but i DID pull those resistors and the cap between them and put in a proper bias circuit. Didnt change anything else until I really get to know the amp and can judge changes better.

EDIT: And my tube chart says AB763.. not the most reliable info :D

[AlRob]

Well he's gonna sell it to me for $1100. It looks like its in pretty good shape from the pictures. I'll have some of the blackface mods done on it. I guess you never know until you play it. What do you think?

http://www.docksidemusic.com/images/SRF.jpg

http://www.docksidemusic.com/images/SRB.jpg

[soldersucker]

I dunno you aren't in the boonies Philly is a big city right? there has to be BF around for that coin if you have cash in hand.Super's though a great great amp have fallen out of market favour do to weight/shape/size and volume.Hey i have 4 and love'm to death but can only wind one up 2-3 gigs a year. People are maybe asking a few hun more for BF but truth be told not many are getting it.
And.......apart from the nicer cab this one has nothing on a say 70-74 that say's 45watts under the speaker jack.These also tend to come with CTS alnico's and have even less of the CBS cathode/fixed bias nonsence to deal with.One of these 70-74ish may set you back 7-800 and you have your cap job tidy-up by your tech paid for.IMHO.

[1guitarslinger]

I dunno you aren't in the boonies Philly is a big city right? there has to be BF around for that coin if you have cash in hand.

+1.0

[Bruce Bennett]

I agree with wizard.. Don't listen with your eyes.. try useing your ears first..

Mystery Vibe and VooDoo.. guys will use this to sell an amp that just ins't moving otherwise..

I'm laughing because I remember a time when the AB568 circuit was being touted as "The one to own" ( 1991-ish)
I swear this crap changes to suit whats sitting in these Vintage guys stores.