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Post subject: My Fender Super Reverb Silverface Project
Posted: Thu Nov 11, 2010 7:17 pm
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Pics can be found here:

http://imaging.taskerworks.com/GalleryT ... ery=442890

My Story: have been a guitar player for a while, just a fun loving amateur and have my son and daughter now in lessons.

A while back, in a local garage sale, I found a beaten up Fender SR SF and thought it could be a fun project - so I offered $50 and took it home. It has been collecting dust for a while as I have been too busy to start the project. I did at one point power it up and it made music. It was not 100% by any stretch and some functions did not work, but at least there was life :-)

So now that I have time I found this forum, and many other resources, and started to wonder what I actually had acquired.

So here is the list of what I have found out so far:
1) tube location sticker says it is circuit AB763
2) front panel has the black lines
3) Rectifier is 5U4
4) Bias circuit goes into apex of 220K ohm resistors
5) Cabinet has replacement speakers
6) Speaker baffle is screwed into place
7) Speakers are staggered on baffle
8) Trannies have dates of 67 and 68
9) all internal wiring is cloth covered
10) Speaker baffle has no edge/lip

So it looks like some kind of hybrid. But it would appear I was lucky to find an AB763 circuit. Is it early enough to be a blackface amp in a silverface dress? How can I tell?

First order of duty is to do the PS caps replacement and I will do the 3 prong plug upgrade. What else should I be doing? Is there a safe way to test if I don't have a variac? Under no load/no speakers plugged in?

But to say I am jazzed about this project is now a large understatement. My wife is going to hate this.....

Chris


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Posted: Thu Nov 11, 2010 8:26 pm
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Chris, I'll offer a few suggestions: 1) replace the bias cap with a 50uf/100vdc; check bias res 470ohm1watt; 2) replace power tube screen resistors with 470ohm2watt flameproof; 3) check the 1500 swamper resistors on the power tube sockets. I would build a light bulb in series current limiter, for initial power-up and checking for shorts in the amp. I'm not computer savvy enough to draw this out and post, but it should be available on some site. It's very simple and effective. As for the Caig cleaners, I use a 2-step method : D5 to clean and S5 as a preservative( not much is needed), seems like Caig changes the names quite often, so use your own best jugement. You can Email me if you can't find a diagram for the current limiter and I'll snail-mail a copy. Art

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Posted: Thu Nov 11, 2010 8:59 pm
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aclempoppi wrote:
Chris, I'll offer a few suggestions: 1) replace the bias cap with a 50uf/100vdc; check bias res 470ohm1watt; 2) replace power tube screen resistors with 470ohm2watt flameproof; 3) check the 1500 swamper resistors on the power tube sockets. I would build a light bulb in series current limiter, for initial power-up and checking for shorts in the amp. I'm not computer savvy enough to draw this out and post, but it should be available on some site. It's very simple and effective. As for the Caig cleaners, I use a 2-step method : D5 to clean and S5 as a preservative( not much is needed), seems like Caig changes the names quite often, so use your own best jugement. You can Email me if you can't find a diagram for the current limiter and I'll snail-mail a copy. Art


Thanks Art - I know about the light bulb current limiter now :-) Good to know.

And like your suggestions. Now I just have to wait for parts .....

Thx, Chris


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Posted: Thu Nov 11, 2010 10:28 pm
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aclempoppi wrote:
Chris, I'll offer a few suggestions: 1) replace the bias cap with a 50uf/100vdc; check bias res 470ohm1watt; 2) replace power tube screen resistors with 470ohm2watt flameproof; 3) check the 1500 swamper resistors on the power tube sockets. I would build a light bulb in series current limiter, for initial power-up and checking for shorts in the amp. I'm not computer savvy enough to draw this out and post, but it should be available on some site. It's very simple and effective. As for the Caig cleaners, I use a 2-step method : D5 to clean and S5 as a preservative( not much is needed), seems like Caig changes the names quite often, so use your own best jugement. You can Email me if you can't find a diagram for the current limiter and I'll snail-mail a copy. Art


+1 on all recommendations.

Looking the pics over, I find that the trannies are a mix of '67 and '68 components.

OT -- 27th week of '67
choke -- 43rd week of '67
PT -- 4th week of '68
RT -- 3rd week of '68

Assuming that these are all original to the chassis -- and I have every reason to believe that they are -- that makes this SR an early '68, probably shipping from Fullerton sometime in early March. The cab and the baffle are likely original to the chassis. And it looks like the amp spent several decades in some dive as a "house amp"......I've never seen nicotine accumulations quite that prolific. I cannot determine anything about those replacement speakers -- they remind me of early Marslands as used in some older Traynors. If they sound good keep them, at least for the time being. For a fifty-dollar "project amp" one could surely do a whole lot worse.

Arjay

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Posted: Fri Nov 12, 2010 3:24 am
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The amp have the blue capacitors ; the real good one of the Black Face area. Congratulation.

About the speakers it look to be RSC, Radio Speaker of Canada. IMO it's ok for now but they are cheap guitar speaker. When your amp will work fine, plan to replace them and you will appreciate the fantastic sound of your Super Reverb.

I agree with aclempoppi. And check if the fuse is the good value....


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Posted: Fri Nov 12, 2010 7:18 am
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Thanks again everyone.

Another question. Are the 25 mfd/25v double caps anything I need to be concerned about? Are they just filter caps?

Also for the 50 mfd/100V cap, it seems to be an odd combination - for example, Tubes and More don't have it in the Sprague Atom. They have a 40mfd/400V - can I sub this with 40mfd 500v or is the 50/100 combo magic :-)

Not sure if you can see, but the bias cap in the amp is virtually unreadable, so this was very timely advise as well.

Last question. I in the picture:

http://app.onlinephotofiler.com/Gallery ... 8&mt=Photo

There is a cap (almost center of picture) in parallel with a resistor just to the left of the optoisolator. The diagram shows it as 25mfd/25v but mine is pretty unreadable. Anything special about that one I need to know? Since it looks worse for wear , I will replace so is a Sprague Atom ok for that swap?

Thx Chris


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Posted: Fri Nov 12, 2010 1:22 pm
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Look there you'll find the layout if you don't have it. You'll see the rigth values.

http://www.ampwares.com/schematics/supe ... _ab763.pdf



You can put a 40 Mfd 400v for bias circuit, nothing to do with the tone. Your other caps at left to opto coupler is also 25 Mfd 25 Volts like you have on other tubes


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Posted: Fri Nov 12, 2010 8:58 pm
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I believe those 25mfd/25 VDC lytics are bypass caps off the cathode of your 12AT7 and 12AX7's. I'd replace them with new Sprague 25mfd/50 VDC ones. Higher voltage rating is better agaist heat and excess outlet voltage. New Atoms are actually smaller in size than the original caps. They will also increase the bass & transient response versus old, dried up caps. So, yes these can effect the tone... quite a bit.

The 50mfd/100 VDC are prolly filter caps in the BIAS power supply. As Art sed, higher voltage rating should not be an issue. Try to keep mfd as close to original. BTW... I also change out the diode in the BIAS power supply. UF4004 is a good sub for most amps. WATCH THE POLARITY of components in this part of circuit, please!

I try to reform ALL lytics' (even "new" ones). You really never know how long they have been sitting on a shelf. Plus, slow ramping with a Variac helps to catch mis-wiring, before the "fireworks show."

Good luck. I used to own a BF Super Reverb. The one amp I wish I never sold.

8^)


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Posted: Sat Nov 13, 2010 2:44 am
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The 25 Mfd ,bypass cap, yes they are bypass cap. A new quality won't change the tone unless your old one is defective .So the new one will give you the best Fender tone as original.
So put good quality ones.
About the bias cap more Mfd will kill some noise send to your 6L6 by the bias voltage, So go ahead ,100 Mfd is a good choice.
Tubes and more have Sprague Atom 100Mfd 100 volts part no C-SA-100-100

You can use also F & T caps, they are good one ( tubes and more)

IMO no need to reforms new caps. I reform old caps to save them, sometimes it's work sometines not.
New caps, don't need that. And you have enough work to do and things to learn so forget that for now.


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Posted: Sat Nov 13, 2010 9:57 am
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BMW2002Ti wrote:
Good luck. I used to own a BF Super Reverb. The one amp I wish I never sold.


From your lips to God's ear!

My first new store-bought Fender amp was a '67 silverface Super Reverb......

Image

Arjay

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Posted: Sat Nov 13, 2010 12:00 pm
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Nice picture, thank's Retroverbial


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Posted: Sat Nov 13, 2010 8:19 pm
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Yeah I agree with Stratele, go with the 100/100 cap for the bias supply filter. Looked up some 50/100 caps and they ranged $3-$11.50( +ship) for good ones. Since this supply is a dedicated tap off the PT, the 100uf is fine. If it were a bias supply off the HT(like a Princeton Reverb) then the uf would have to be kept smaller, because of the cap charge-up time. As for the double bypass caps they can be replaced with single 25uf/25vdc caps for each cathode. But some jockeying of resistors would be needed. So i wouldn't focus on these until the rest of the amp is up and running. Forming the caps is another ballgame. I've used the variac method for years, but found a less random current limiting method. The later uses the amp as a gradual current supply, but requires the addition and removal of some resistors and about 36 hours of an open chassis running on power. Use the bulb limiter, and all should be well. Art........Great pics, Arjay ! And your collection never ceases to amaze me !

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Posted: Sun Nov 14, 2010 1:11 am
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Thanks, Art.

I may have an addition to the herd tomorrow......

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Posted: Sun Nov 14, 2010 4:49 am
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Thanks All

Parts are on order and when they arrive the work will begin.

Another question. I will do the 3 prong power update - should I do the death cap mod at that time as well? Is it a recommended mod?

Rgds, Chris


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Posted: Sun Nov 14, 2010 5:08 am
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The death cap ... you mean the by- pass cap on AC line. If you want to replace it and go to 0.002 μf ( not bigger) at 1Kvolts to 5 Kvolts


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