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Post subject: Fender Super Reverb silver face Question
Posted: Sun Oct 06, 2013 2:07 pm
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I just bought a Fender Super reverb silver face 1973/4 and I am wondering about the bias pot. I would like to change it to black face specs ..and it seems like someone has been in there messin around with it... has anyone seen this set-up before? seems like it should sound better than it does... any suggestions? thanks Jim

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Post subject: Re: Fender Super Reverb silver face Question
Posted: Sun Oct 06, 2013 5:43 pm
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Jimitrader,

It doesn't appear to be converted to AB763. Compare the resistors & wiring on pot in the areas circled in red to my AB763 modded SFSR. Check against the schematic:


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Last edited by BMW2002Ti on Sun Oct 06, 2013 5:53 pm, edited 1 time in total.

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Post subject: Re: Fender Super Reverb silver face Question
Posted: Sun Oct 06, 2013 5:45 pm
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Schematic & layout (site seems to allow only two URL's per post, again):

AB763:

http://www.webphix.com/schematic%20heav ... _schem.pdf



Yours looks like a AA270 circuit:

http://www.webphix.com/schematic%20heav ... _schem.pdf


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Post subject: Re: Fender Super Reverb silver face Question
Posted: Sun Oct 06, 2013 9:09 pm
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thanks for responding and the pix!!

do you think i should remove the purple circled items including the parasitic caps on tube pins? what is the little thing on the far right with a spring?

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Post subject: Re: Fender Super Reverb silver face Question
Posted: Sun Oct 06, 2013 9:53 pm
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Jimitrader,

If you are going to keep this amp as AA270 format --- leave the ceramic discs, anti-parasitic caps on the amp. The PI of the AA270 is setup much hotter than the AB763. You risk oscillations by removing those caps.

The extra electrolytic cap in the bias supply is OEM for the AA270 (see schemo and layout). Leave it attached. You may want to wrap the solder point with tape or use a heat-shrink insulation (right at the bottom of the fuscia circle you made). This wire cannot touch ground --- or you risk losing your bias voltage. And the 6L6GC's going ballistic.

The "springy thing" looks like an oldtime pigtail connector. Ot perhaps an air-core choke. Need a better view of it.

Air-core balun or choke:

http://www.bizrice.com/upload/20120118/ ... ductor.jpg



AA270 circuit and layout:

http://www.webphix.com/schematic%20heav ... _schem.pdf


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Post subject: Re: Fender Super Reverb silver face Question
Posted: Mon Oct 07, 2013 2:55 am
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It look the balance pot for bias is mod for an adjustable bias pot .

Many Silverface have a bias balance pot not a bias adjstment pot like Blackface. Your amp balance pot look modified to Blackface bias pot.

Sound good to you ? Don't remove any of those parts . Bad lead dress on some Silverface need the 2 ceramic caps


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Post subject: Re: Fender Super Reverb silver face Question
Posted: Mon Oct 07, 2013 12:37 pm
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I am following the Gerald Weber video tutorial and he says to put the mm to MA and put pos red lead on center tap and black lead on pin 3 of 6v6 tubes and compare readings. I am getting 2.2? seems the goal is 25 what am i doing wrong?

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here is a pic where i circled the spots where i connect..in standby then flip power on and check.?


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Post subject: Re: Fender Super Reverb silver face Question
Posted: Mon Oct 07, 2013 1:17 pm
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Your volmeter must read MA, milliamps not Volts. Di you know

This is a very dangerous voltage there . You have some high voltage on both test probe , on BOTH hands . This can kill you.

I never do that way .


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Post subject: Re: Fender Super Reverb silver face Question
Posted: Mon Oct 07, 2013 1:28 pm
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if i post a picture of my meter could you help me figure out how to set it to MA it is confusing me..thanks J
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Post subject: Re: Fender Super Reverb silver face Question
Posted: Mon Oct 07, 2013 2:51 pm
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Good photo .

You must set your meter at 1/4 turn on right side , 200 m "A" scale.


Be carefull , lethall voltage there.
__________________________________________________________________
This reading is esier and safer with a 1 oms resitor from pin 8 to ground . You must disconnect actual pin to ground to solder a new resistor there . The resistor can stays there for the life. no need to remove after test.


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Post subject: Re: Fender Super Reverb silver face Question
Posted: Mon Oct 07, 2013 3:02 pm
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thanks I discharge amp.. first ..then apply alligator clip leads from mm...then turn on mm then power up amp in standby ...then turn on amp power...and i get 00.0 on meter ? is my meter broke? or the fuse maybe? i just downloaded the manual and contacted them for tech support to see if its the meter??..I am being safe thats top priority!!! no amp project is worth my life that's for sure.....thanks for the response..J


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Post subject: Re: Fender Super Reverb silver face Question
Posted: Mon Oct 07, 2013 3:13 pm
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Meter in "A " ( ampere scale ) are easy to blow a fuse . If you use your meter for volts reading and you make a mistake to put meter on "A" scale , fuse burn.


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Post subject: Re: Fender Super Reverb silver face Question
Posted: Mon Oct 07, 2013 3:43 pm
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it was the fuse in the mm..!! the thing is so cheap that the metal that holds it in place was loose and the fuse was falling out!!! good to know for others who may have same problem? anyway now i am getting a real reading...29.1 and 27.3 does that seem pretty good or kinda high?


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Post subject: Re: Fender Super Reverb silver face Question
Posted: Mon Oct 07, 2013 3:51 pm
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Just to clarify, exactly what type of output tubes are in this amp?

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 silver face Question
Posted: Mon Oct 07, 2013 3:56 pm
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6l6 ge


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