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Post subject: Re: fender super reverb silver face hum problem
Posted: Sun Nov 09, 2014 1:41 pm
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Location: Iran - Tehran
stratele52 wrote:
ali_k wrote:
dear friends after checking and correcting the polarity of the filter caps (combination of original old caps and two taiwanese cap) , thankfully the hum is GONE :-)
but still one problem remains, after turning down the volume knobs to zero ( in both channels) the amp is not mute and sound of guitar still heard from speakers...

other thing is , the sound is little bit harsh and it is not crystal clear and smooth sound.



Please replace all these caps first , see my last post .

i just try to correct the right order and polarity of previous caps...that's all...
but i will buy some high quality caps for filter caps , then tell you the results about the harshness of sound and volume problem...also i will order the jj tubes ,,,
can i order only 2 6l6gc and one gz34 and use previous japanese pre amp tubes or buy the complete set?


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sun Nov 09, 2014 1:48 pm
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i think the Chassis that "ab763" written on it is wrongly replace, because the Chassis is not belong to this circuit...


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sun Nov 09, 2014 2:13 pm
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Ali, it's an AB568 circuit. "Sandbox" resistors and disc caps on the 6L6GC. Plus, the arrangement of the bias supply pot and resistors = AB568.

Check the layout:


http://bmamps.com/Schematics/fender/sup ... layout.gif


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sun Nov 09, 2014 3:06 pm
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ali_k wrote:
[
can i order only 2 6l6gc and one gz34 and use previous japanese pre amp tubes or buy the complete set?




To do first;

Replace all filter caps ( see BMW answer ) .
And I would say replace all small white electrolitics cap , ( 25 mfd 25 volts ) these are often bad .

___________________________________
The original AB568 use 5U4 if your one is good, keep it , same for 6L6s

Some of your Japanese 12XX7 could be worn or noisy .

We can't know without some tests


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sun Nov 09, 2014 3:22 pm
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ali_k wrote:
i think the Chassis that "ab763" written on it is wrongly replace, because the Chassis is not belong to this circuit...



CBS do some poor job


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sun Nov 09, 2014 3:32 pm
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stratele52 wrote:
ali_k wrote:
dear friends after checking and correcting the polarity of the filter caps (combination of original old caps and two taiwanese cap) , thankfully the hum is GONE :-)
but still one problem remains, after turning down the volume knobs to zero ( in both channels) the amp is not mute and sound of guitar still heard from speakers...

other thing is , the sound is little bit harsh and it is not crystal clear and smooth sound.



Please replace all these caps first , see my last post .



+1

No one here can answer your question about "harsh" sound (wtf does that mean?)

Replace ALL electrolytic caps, (the 5 caps in the filter section, the 7 cathode bypass caps, the bias supply cap, and the 5uF non-polarized cap at the power tubes.)

While you are doing that, I'd also replace the resistors on the filter board, and replace the 2 prong power cord with a 3 prong cord and get rid of the death cap.

This amp is a long way from being "fixed" just because the hum is gone.

First you need to follow the instructions already given here by stratele52 and bmw2002tii, then worry about why the amp has or doesn't have hum, or doesn't sound right, or is not completely muted when the volume knob is turned to zero.

Continuing to operate this amp in its current state runs the risk of possible damage to the power transformer and other components which will just make it more expensive to repair.

vinyl


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Post subject: Re: fender super reverb silver face hum problem
Posted: Mon Nov 10, 2014 2:22 am
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Check if fuse is the right one , sometimes people put a too much powerfull fuse wich can damage the amp .

Put one with original specs only ,


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Post subject: Re: fender super reverb silver face hum problem
Posted: Mon Nov 10, 2014 12:34 pm
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Follow the advice given to be sure.

Often what people think is the sound of a vintage amp is simply a tired amp loaded w/ resistors and caps which are out of spec, even though the amp still 'works'.

Personally, I would also check every component w/ a DMM and/or a Cap tester to insure that all are in spec, and replace those which are not.

If you want it sounding as close to the way it left Fullerton, that's the thing to do.

cheers!

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Post subject: Re: fender super reverb silver face hum problem
Posted: Wed Nov 12, 2014 12:03 pm
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can i put GZ34 instead of 5u4gb on ab568 circuit?
the sound will be better if i put gz34 or not?
i mean that if i want to use some overdrive/distortion pedals with super reverb amp,
which rectifier is best choice to support OD/Dist. effects and also which
parts, elements or caps of amp must be change to get better sounds with OD/Dist. pedals with super reverb amp...
i know it has very nice clean tone but for getting nice overdrive tone,
please help me friends for this issue...


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Post subject: Re: fender super reverb silver face hum problem
Posted: Wed Nov 12, 2014 12:28 pm
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ali_k wrote:
can i put GZ34 instead of 5u4gb on ab568 circuit? Yes , with bias check
the sound will be better if i put gz34 or not? No

i mean that if i want to use some overdrive/distortion pedals with super reverb amp,
which rectifier is best choice to support OD/Dist. effects and also which
parts, elements or caps of amp must be change to get better sounds with OD/Dist. pedals with super reverb amp...
All O.D. / dist are no the same , each have different specs / flavor /tone . It is a case by case IMO
For rectifier , anyone


i know it has very nice clean tone but for getting nice overdrive tone,
please help me friends for this issue...


Each amp are different , not same tubes brand , years , this change the tone too


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Post subject: Re: fender super reverb silver face hum problem
Posted: Wed Nov 12, 2014 8:34 pm
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Location: Iran - Tehran
stratele52 wrote:
ali_k wrote:
can i put GZ34 instead of 5u4gb on ab568 circuit? Yes , with bias check
the sound will be better if i put gz34 or not? No

i mean that if i want to use some overdrive/distortion pedals with super reverb amp,
which rectifier is best choice to support OD/Dist. effects and also which
parts, elements or caps of amp must be change to get better sounds with OD/Dist. pedals with super reverb amp...
All O.D. / dist are no the same , each have different specs / flavor /tone . It is a case by case IMO
For rectifier , anyone


i know it has very nice clean tone but for getting nice overdrive tone,
please help me friends for this issue...

I cannot understand, please more describe

Each amp are different , not same tubes brand , years , this change the tone too


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Post subject: Re: fender super reverb silver face hum problem
Posted: Thu Nov 13, 2014 12:05 am
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So many thanks my friends


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Post subject: Re: fender super reverb silver face hum problem
Posted: Thu Nov 13, 2014 1:27 am
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Good luck! :mrgreen: :thumbsup: :mrgreen:

Tell us your results.


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Post subject: Re: fender super reverb silver face hum problem
Posted: Thu Nov 13, 2014 2:16 am
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ali_k wrote:
I cannot understand, please more describe




Describe what ?

All ? Sorry too long to write :(


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Post subject: Re: fender super reverb silver face hum problem
Posted: Thu Nov 13, 2014 8:22 am
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Joined: Fri Nov 07, 2014 7:33 am
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stratele52 wrote:
ali_k wrote:
I cannot understand, please more describe




Describe what ?

All ? Sorry too long to write :(

no need to describing anymore dear stratele52, now i'm completely understand :)
thank you again for you kind help...
after fixing the amp by amp tech that i'm recently meet him, i'll tell you the results...
but one thing, the original filter caps are very very expensive for me and i'll decided to find some real "made in Japan" caps instead of F&t and other expensive caps, so hope that i get nice sound with these caps...


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