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Post subject: fender super reverb silver face hum problem
Posted: Fri Nov 07, 2014 10:10 am
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Hi everyone,
my super reverb silver face (AB763 circuit) amp has 2 major problem,
when i turn down both normal channel/vibrato volume knob, the amp still has sound and the volume knob didn't mute the sound that coming from speakers but amp never has hum or extra noise, i change the volume knob with new one but the problem isn't solved...

i thought that if i'm change the original filter caps with new one( the new caps are build in taiwan or china) so the problem should solve but was not solved, this time i decided to replace the new caps with original caps but unfortunately amp get some HUM even when no cable attached to amp and the volume knob is totally closed...
i must tell that my amp has 2 6l6 west germany tubes and i put 5U4GB tube for smoother tones
please help me about this issue


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Post subject: Re: fender super reverb silver face hum problem
Posted: Fri Nov 07, 2014 12:30 pm
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Adjust the hum balance pot for least hum. 6L6GC's were never made in Germany, as far as I know. You may have Russian made, relabeled tubes.

Try to buy quality filter caps. F&T (of Germany) makes some of the best on the market today.


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Post subject: Re: fender super reverb silver face hum problem
Posted: Fri Nov 07, 2014 12:47 pm
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One weak 6L6 may hum . Bad heater center tap may hum or if amp use two 100 ohms resistors for artificial center tap , on heater circuit check them .

Pots ; what is the value you read ( with tester ) in ohms ?

Tube Amp Doctor , a Germany tube reseller ?

Follow BMW advice


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Post subject: Re: fender super reverb silver face hum problem
Posted: Fri Nov 07, 2014 9:29 pm
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BMW2002Ti wrote:
Adjust the hum balance pot for least hum. 6L6GC's were never made in Germany, as far as I know. You may have Russian made, relabeled tubes.

Try to buy quality filter caps. F&T (of Germany) makes some of the best on the market today.

You're correct my friend, the tubes are Russian but labeled west germany
I want to buy complete Jojo tube set and change all power/pre amp tubes...
Where's hum balance pot and how I should adjust it?


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Post subject: Re: fender super reverb silver face hum problem
Posted: Fri Nov 07, 2014 9:42 pm
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stratele52 wrote:
One weak 6L6 may hum . Bad heater center tap may hum or if amp use two 100 ohms resistors for artificial center tap , on heater circuit check them .

Pots ; what is the value you read ( with tester ) in ohms ?

Tube Amp Doctor , a Germany tube reseller ?

Follow BMW advice

As I mentioned, the 6l6 are Russian, and the preamp tubes are japanese
I put 5u4gb for lower attack and smoother and warmer sound... You think it works or I must put gz34?
Attack of amp is little bit high and the sound is harsh, I think tereble was distorted and make bad sound it

Also in both channels , when I turn down volume to zero, it didn't completly mute ,
Please tell me where is the test point for checking ohms?


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sat Nov 08, 2014 1:54 am
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ali_k wrote:
[quote="stratele52" preamp tubes are japanese Vintage tubes ?
I put 5u4gb for lower attack and smoother and warmer sound... You think it works or I must put gz34?
Attack of amp is little bit high and the sound is harsh, I think tereble was distorted and make bad sound it
Low voltage may do that , try a know good GZ34

Also in both channels , when I turn down volume to zero, it didn't completly mute ,
Please tell me where is the test point for checking ohms?
Disconnect one side ( lug ) of each pot and connect your meter test probes to the externals lugs of the pot. The center lug can be connected to the circuit




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Post subject: Re: fender super reverb silver face hum problem
Posted: Sat Nov 08, 2014 2:12 am
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stratele52 wrote:
ali_k wrote:
[quote="stratele52" preamp tubes are japanese Vintage tubes ?
I put 5u4gb for lower attack and smoother and warmer sound... You think it works or I must put gz34?
Attack of amp is little bit high and the sound is harsh, I think tereble was distorted and make bad sound it
Low voltage may do that , try a know good GZ34

Also in both channels , when I turn down volume to zero, it didn't completly mute ,
Please tell me where is the test point for checking ohms?
Disconnect one side ( lug ) of each pot and connect your meter test probes to the externals lugs of the pot. The center lug can be connected to the circuit



The Japanese tube are vintage and I'll change all of them with Jojo tubes set
Thank your for your solution but its such a complicated job for me...would you please send me some pictures or give me more detailed instructions...


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sat Nov 08, 2014 2:20 am
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You are better to see a qualified tech .Sorry I can't help you more :(

What is a jojo tube ?


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sat Nov 08, 2014 2:36 am
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stratele52 wrote:
You are better to see a qualified tech .Sorry I can't help you more :(

What is a jojo tube ?

Thank you so much,,,,I'm so sorry...it's JJ tubes
http://www.amazon.com/gp/aw/d/B0057IPPG ... 15&simLd=1


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sat Nov 08, 2014 2:43 am
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These are good tubes.

The best is to mix many brand of 12XX7 tubes in same amp . But all JJ's are good an easy choice too


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sat Nov 08, 2014 3:13 am
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stratele52 wrote:
These are good tubes.

The best is to mix many brand of 12XX7 tubes in same amp . But all JJ's are good an easy choice too

Need to Change filter caps with new one or keep the original caps?
http://postimg.org/image/7czgxmiu3/


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sat Nov 08, 2014 3:34 am
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The green cap look have something "burn " on the top we see !!!!

Replace them all old original one and Taiwan cheap one , follow BMW advice . Replace bias circuit filter cap too .

Check polarity carrefully .


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sat Nov 08, 2014 4:47 am
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stratele52 wrote:
The green cap look have something "burn " on the top we see !!!!

Replace them all old original one and Taiwan cheap one , follow BMW advice . Replace bias circuit filter cap too .

Check polarity carrefully .

For better and smoother sounding , or also modifying to blackface ,which parts must be change?


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sat Nov 08, 2014 4:57 am
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AB763 is a Blackface
http://ampwares.com/?brand=fender&era=b ... line=super

Your amp need to see a qualify tech


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sat Nov 08, 2014 5:30 am
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stratele52 wrote:
AB763 is a Blackface
http://ampwares.com/?brand=fender&era=b ... line=super

Your amp need to see a qualify tech

But front panel of amp is sliver...I'm wodering


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