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Post subject: Re: Fender super reverb SF ab763 modification
Posted: Mon Jul 15, 2019 5:42 pm
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I'd prolly sell the Fender and look for a Marshall to replace it.


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Post subject: Re: Fender super reverb SF ab763 modification
Posted: Mon Jul 15, 2019 6:28 pm
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ali_k wrote:
actually i think the super reverb have not compressed sound , so the distortion and fuzz sounds are prrety fizzy and harsh , therefore i'm looking for some improvement of my fender super reverb circuit...
And other important thing is i dont want to spend extra money for buying new amp.

This is exactly what the problem is.
As mentioned above, when it is said that Jim Marshall copied his design from the Fender Bassman, that does not mean that he used the Silverface or even Blackface Bassman.
Those old tweed amps would compress, and growl, and snarl, and did NOT have a lot of clean headroom. Anything from 6-12 and you were not adding volume... just compression and dirt because your tubes were saturated.

To do that with a Silverface would require far more than a "mod"... it would require a complete rebuild from the chassis up, and the transformers may or may not be suitable for the sound you are after.

Honestly... you have the wrong amp if you want saturated and compressed distortion. The Silverface amps were designed to be sparkly clean and they do that quite well. To get any dirt out of them, they have to be LOUD!

Modifying an AB763 will cost you more in lost value of the amp than it would cost you to sell it and buy a JCM800.

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Post subject: Re: Fender super reverb SF ab763 modification
Posted: Mon Jul 15, 2019 8:27 pm
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A quick google search reveals Gilmour only Fendered with Twins, not a Super.
The super is brighter because of smaller, brighter speakers and a smaller midrange cap in the tone stack

The harshness comes from too much Treble, a common Super issue. The EQ pedal should take care of that, so the amp may need a little help if it didn't.

Changing out the mid cap from .02 to .047 and the phase inverter cap from .001 to .01 will match the Twin specs. It will lower Treble and focus on midrange tones.

The speaker harshness can be tamed with 4 inch disks of 3/4" open pore foam. Sew these gently into the backside of the speaker grille in front of the center of the cones.


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Post subject: Re: Fender super reverb SF ab763 modification
Posted: Tue Jul 16, 2019 1:25 am
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May be you whee never like your amp but are you sure your Super Reverb is in good working order ?

Tubes are good ? And are the right one ? With bias check for power tubes
Filter caps are changed for new ones.
No mods over years


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Post subject: Re: Fender super reverb SF ab763 modification
Posted: Tue Jul 16, 2019 4:43 am
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CB91710 wrote:
ali_k wrote:
actually i think the super reverb have not compressed sound , so the distortion and fuzz sounds are prrety fizzy and harsh , therefore i'm looking for some improvement of my fender super reverb circuit...
And other important thing is i dont want to spend extra money for buying new amp.

This is exactly what the problem is.
As mentioned above, when it is said that Jim Marshall copied his design from the Fender Bassman, that does not mean that he used the Silverface or even Blackface Bassman.
Those old tweed amps would compress, and growl, and snarl, and did NOT have a lot of clean headroom. Anything from 6-12 and you were not adding volume... just compression and dirt because your tubes were saturated.

To do that with a Silverface would require far more than a "mod"... it would require a complete rebuild from the chassis up, and the transformers may or may not be suitable for the sound you are after.

Honestly... you have the wrong amp if you want saturated and compressed distortion. The Silverface amps were designed to be sparkly clean and they do that quite well. To get any dirt out of them, they have to be LOUD!

Modifying an AB763 will cost you more in lost value of the amp than it would cost you to sell it and buy a JCM800.

Super reverb does not have master volume, so can i use variac for lowering the voltage and crancking the amp for better sound in lower volumes?
I heard Variac will kill the amp and tubes, what is your idea?

Is it better to add master volume
on super reverb circuit or buy a variac?


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Post subject: Re: Fender super reverb SF ab763 modification
Posted: Tue Jul 16, 2019 4:50 am
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stratele52 wrote:
May be you whee never like your amp but are you sure your Super Reverb is in good working order ?

Tubes are good ? And are the right one ? With bias check for power tubes
Filter caps are changed for new ones.
No mods over years

The 6l6 tubes are russian but they're in good condition, also preamp tubes are good.
I recently change all the caps( filter, bias,...) with high quality japanese caps. also Power trans, chokes are ok.
I didnt change any resistors. Because they're in good condition.
But i never did bias after replacing the caps.
because i dont exactly know how to bias.


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Post subject: Re: Fender super reverb SF ab763 modification
Posted: Tue Jul 16, 2019 9:02 am
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Amp look in good condition except about bias we don't know.
A good bias is a must for a good tone;

A correctly biased amp will run efficiently and maximizes the life of your tubes.

Under - biased (hot ) amps will lack of punch and tubes will run hotter , shorter tube's life .

Overbiased amps ( cold ) will sound thin and brittle. with tubes running too cool for proper performance .
A correctly biased amps will sound clean and tight a moderate volumes, than at higher volumes breakup and distort musically .


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Post subject: Re: Fender super reverb SF ab763 modification
Posted: Tue Jul 16, 2019 3:24 pm
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Is this the same amp you posted about in this thread?
https://forums.fender.com/viewtopic.php?f=12&t=96698

It was determined in that thread that the amp was an AB568 circuit.

As has been posted here ad nauseum, you can't go by the circuit number on the tube chart of a silverface amp.

If you modded it to an ab763 since then, then the replies about adjusting bias are appropriate.

Fender amps are generally noted for their "scooped" mids. From what I've read Gilmour used mostly Hiwatt amps which have a lot of midrange. He played them clean and used pedals for dirt, compression etc.

You might want to check out this page:
http://www.gilmourish.com/?page_id=3389


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Post subject: Re: Fender super reverb SF ab763 modification
Posted: Tue Jul 16, 2019 3:38 pm
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vinyl wrote:
Is this the same amp you posted about in this thread?
https://forums.fender.com/viewtopic.php?f=12&t=96698

It was determined in that thread that the amp was an AB568 circuit.
[/url]



:shock:


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Post subject: Re: Fender super reverb SF ab763 modification
Posted: Mon Oct 07, 2019 10:40 am
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Hi friends, i re-capped "All" the capacitors with new high quality japanese caps,hopefully the hum and all extra noises are gone, the sounds is "ok" right now but i have some problems:

1- after turning down the volume knob in both channells, the amp is not silent and it has very little sound, and the sound of guitar is already coming out from the amp even though the volume is totally off.
( i cleaned the pot with volume cleaner but the problem is not solve)

2- when i rotating the middle knob, the amp sound is affeceted with mentioned knob and volume begins to raise up or raise down along side the middle knob.

3- when i put the volume knob on 1; the amp sound is super huge loud. And i forced to put volume near 0 for getting low and bedroom volume.

I must say that all tubes are old but they are in good condition.

After the recaping i didnt bias the amp because I dont know how to biasing the amp so please help me about biasing.

Thank you for your help.


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Post subject: Re: Fender super reverb SF ab763 modification
Posted: Mon Oct 07, 2019 1:26 pm
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july 10 you wrote ;

" I recently restoration and recap all the capacitors with good quality japanese caps, "......

Now is it the second recap in few month ? :?: :?:
___________________________

1,2,3 ; Did you do some work on the circuit and or pots wiring ?

Post good picture of inside your amp.

How to bias ? Tube use lethal voltage.
You need voltmeter and know hoe to use it
A bis probe or two 1 ohms resistors.

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July 11 Retroverbial wrote ; "What I think is, you don't have a clue as to what you're doing.


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Post subject: Re: Fender super reverb SF ab763 modification
Posted: Mon Oct 07, 2019 2:45 pm
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ali_k wrote:
1- after turning down the volume knob in both channells, the amp is not silent and it has very little sound, and the sound of guitar is already coming out from the amp even though the volume is totally off.
( i cleaned the pot with volume cleaner but the problem is not solve)

2- when i rotating the middle knob, the amp sound is affeceted with mentioned knob and volume begins to raise up or raise down along side the middle knob.

3- when i put the volume knob on 1; the amp sound is super huge loud. And i forced to put volume near 0 for getting low and bedroom volume.

Thank you for your help.


You have done miss-wiring into-&-out of the control pots. Double check your work. Good luck!


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Post subject: Re: Fender super reverb SF ab763 modification
Posted: Mon Oct 07, 2019 4:10 pm
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ali_k wrote:
......but i have some problems.


YA THINK?

Before you go and get yourself *killed* why don't you take the amp to a professional who knows WTF he is doing?

:roll:
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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Post subject: Re: Fender super reverb SF ab763 modification
Posted: Tue Oct 08, 2019 4:16 pm
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BMW2002Ti wrote:
ali_k wrote:
1- after turning down the volume knob in both channells, the amp is not silent and it has very little sound, and the sound of guitar is already coming out from the amp even though the volume is totally off.
( i cleaned the pot with volume cleaner but the problem is not solve)

2- when i rotating the middle knob, the amp sound is affeceted with mentioned knob and volume begins to raise up or raise down along side the middle knob.

3- when i put the volume knob on 1; the amp sound is super huge loud. And i forced to put volume near 0 for getting low and bedroom volume.

Thank you for your help.


You have done miss-wiring into-&-out of the control pots. Double check your work. Good luck!

Please guide me to how to check wiring pots, i think there is problem and conflict with volume pot wiring and mddle pot wiring but i dont know how to check the conflicts of those pots.


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Post subject: Re: Fender super reverb SF ab763 modification
Posted: Tue Oct 08, 2019 4:50 pm
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Joined: Fri Nov 07, 2014 7:33 am
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Location: Iran - Tehran
Retroverbial wrote:
ali_k wrote:
......but i have some problems.


YA THINK?

Before you go and get yourself *killed* why don't you take the amp to a professional who knows WTF he is doing?

:roll:
Arjay

I want to expirience and learn to repair by myself.its such a real fun and joy for me.


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