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Post subject: Re: fender super reverb silver face hum problem
Posted: Fri Nov 14, 2014 7:29 am
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You write ;

" it's seems that you never read or view his books and video's."
Your question is excellent about capacitors 100 and 40 mfd.


Against by the difficulty of discussing by email / forum, if in addition to advise you to repair your amplifier we start discussing a modification, it will be too long amd more expensive.
It could be a lot to do but it's not necessary. Keep the amp original with quality parts is the easiest and you get good sound.

Because for me, the 100 and 40 mfd are among a mods to an amp.

I prefer to stick to the original values with quality parts such as F & T

This amplifier is part of the story even though it is not as sought after as Balckface, I do not change the appearance with a grill cloth.
Especially if you remove the original, this will be very difficult to install if you change your mind. And valu drop .
Diamond , no problem , easy to put back original one .

If you have any question I will be happy to help you


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Post subject: Re: fender super reverb silver face hum problem
Posted: Fri Nov 14, 2014 8:47 am
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stratele52 wrote:
You write ;

" it's seems that you never read or view his books and video's."
Your question is excellent about capacitors 100 and 40 mfd.


Against by the difficulty of discussing by email / forum, if in addition to advise you to repair your amplifier we start discussing a modification, it will be too long amd more expensive.
It could be a lot to do but it's not necessary. Keep the amp original with quality parts is the easiest and you get good sound.

Because for me, the 100 and 40 mfd are among a mods to an amp.

I prefer to stick to the original values with quality parts such as F & T

This amplifier is part of the story even though it is not as sought after as Balckface, I do not change the appearance with a grill cloth.
Especially if you remove the original, this will be very difficult to install if you change your mind. And valu drop .
Diamond , no problem , easy to put back original one .

If you have any question I will be happy to help you

thank you for your kind advice :)


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Post subject: Re: fender super reverb silver face hum problem
Posted: Fri Nov 14, 2014 9:28 am
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Location: Province de Québec, Canada
To resume ;

I will go for G. Weber caps mod . Be sure to understand wich caps ( 2 ) keep with original values


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Post subject: Re: fender super reverb silver face hum problem
Posted: Fri Nov 14, 2014 4:28 pm
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" 1 - Can i put 100 mf 450v instead of 100mf 350v?

2 - gerald weber in his instructional video put only one 40mf and he described that 40mf has better low end sound and also two 20mf on twin reverb amp...can i use this trick for super reverb? "



Answer to 1. Yes, it is ok to use 100mfd/450VDC. And ok to use 100/450 versus 80mfd/350VDC caps. Remember, the first two caps are in series with each other. The total capacitance of that first stage = half of the capacitance of both caps. And the voltage rating is twice each one's value.


50mfd/900VDC for two 100/450 caps in series.

40mfd/700VDC for two 80/350 caps.


A difference of only 10mfd capacitance. But, 200VDC difference in total voltage rating.

This series arrangement is done, because a single 700VDC rated cap of 30-50mfd is very expensive and hard to find.



answer to 2. 40mfd is fine, PROVIDED it is 700VDC or more rated. I would not put a single 40mfd/500VDC rated cap in the first stage. And if you do find a 700VDC voltage rated single cap, you will need to remove the two 220k-ohm, 2-watt leveling resistors between the two first stage filters.


I have used two 100mfd/450VDC caps in many of the GZ34 and solid-state rectified amps I've redone. No problems. The combined voltage ratings of those first two caps should be as high as possible (1000VDC would be better, but size & cost is impractical) . They bear the brunt of turn on-&-off transients and often are the first to fail.


Good luck with your fix. :mrgreen:


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sat Nov 15, 2014 3:46 am
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BMW2002Ti wrote:
" 1 - Can i put 100 mf 450v instead of 100mf 350v?

2 - gerald weber in his instructional video put only one 40mf and he described that 40mf has better low end sound and also two 20mf on twin reverb amp...can i use this trick for super reverb? "



Answer to 1. Yes, it is ok to use 100mfd/450VDC. And ok to use 100/450 versus 80mfd/350VDC caps. Remember, the first two caps are in series with each other. The total capacitance of that first stage = half of the capacitance of both caps. And the voltage rating is twice each one's value.


50mfd/900VDC for two 100/450 caps in series.

40mfd/700VDC for two 80/350 caps.



A difference of only 10mfd capacitance. But, 200VDC difference in total voltage rating.

This series arrangement is done, because a single 700VDC rated cap of 30-50mfd is very expensive and hard to find.



answer to 2. 40mfd is fine, PROVIDED it is 700VDC or more rated. I would not put a single 40mfd/500VDC rated cap in the first stage. And if you do find a 700VDC voltage rated single cap, you will need to remove the two 220k-ohm, 2-watt leveling resistors between the two first stage filters.


I have used two 100mfd/450VDC caps in many of the GZ34 and solid-state rectified amps I've redone. No problems. The combined voltage ratings of those first two caps should be as high as possible (1000VDC would be better, but size & cost is impractical) . They bear the brunt of turn on-&-off transients and often are the first to fail.


Good luck with your fix. :mrgreen:

Thank you so much for you detailed instructions :)


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sat Nov 15, 2014 4:08 pm
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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.


After reviewing the 568 circuit schematic, the bright switch could cause sound still being heard with the volume turned to zero, if the tone controls are not turned to zero also.

Leave the tone controls where they are, turn the bright switch off, turn the volume to zero, do you still hear sound?

Then turn tone controls to zero ?(treble, mid, bass) do you still hear sound?

vinyl

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"Where confusion abounds, there's money to be made."


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sat Nov 15, 2014 9:49 pm
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vinyl 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.


After reviewing the 568 circuit schematic, the bright switch could cause sound still being heard with the volume turned to zero, if the tone controls are not turned to zero also.

Leave the tone controls where they are, turn the bright switch off, turn the volume to zero, do you still hear sound?

Then turn tone controls to zero ?(treble, mid, bass) do you still hear sound?
I will ask my amp tech to use your instructions, also amp tech said that he want to use some high quality volume potentiometer to solve volume problem

vinyl

I will ask my amp tech to use your instructions, also amp tech said that he want to use some high quality volume potentiometer to solve volume problem...
So you think this the nature of ab568 that never completely close the volume level in both channels?


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sat Nov 15, 2014 9:51 pm
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Location: Iran - Tehran
ali_k wrote:
vinyl 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.


After reviewing the 568 circuit schematic, the bright switch could cause sound still being heard with the volume turned to zero, if the tone controls are not turned to zero also.

Leave the tone controls where they are, turn the bright switch off, turn the volume to zero, do you still hear sound?

Then turn tone controls to zero ?(treble, mid, bass) do you still hear sound?
I will ask my amp tech to use your instructions, also amp tech said that he want to use some high quality volume potentiometer to solve volume problem

vinyl

I will ask my amp tech to use your instructions, also amp tech said that he want to use some high quality volume potentiometer to solve volume problem...
So you think this is the nature of ab568 that never completely close the volume level in both channels?


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Profile
Post subject: Re: fender super reverb silver face hum problem
Posted: Sat Nov 15, 2014 9:54 pm
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Joined: Fri Nov 07, 2014 7:33 am
Posts: 77
Location: Iran - Tehran
After reviewing the 568 circuit schematic, the bright switch could cause sound still being heard with the volume turned to zero, if the tone controls are not turned to zero also.

Leave the tone controls where they are, turn the bright switch off, turn the volume to zero, do you still hear sound?

Then turn tone controls to zero ?(treble, mid, bass) do you still hear sound?
I will ask my amp tech to use your instructions, also amp tech said that he want to use some high quality volume potentiometer to solve volume problem

vinyl[/quote][/quote]
I will ask my amp tech to use your instructions, also amp tech said that he want to use some high quality volume potentiometer to solve volume problem...
So you think this is the nature of ab568 that never completely close the volume level in both channels?


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Profile
Post subject: Re: fender super reverb silver face hum problem
Posted: Sun Nov 16, 2014 2:10 am
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Joined: Thu Dec 12, 2013 2:54 pm
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I was incorrect in my previous post. :oops: The bright switch does allow signal through to the grid, but with the volume at zero the grid should be at ground potential. That ground is achieved through the physical connection of the volume pot to the chassis, so a loose mounting nut or corrosion could cause the volume to be not completely muted.

vinyl

_________________
"Where confusion abounds, there's money to be made."


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sun Nov 16, 2014 2:46 am
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vinyl wrote:
I was incorrect in my previous post. :oops: The bright switch does allow signal through to the grid, but with the volume at zero the grid should be at ground potential. That ground is achieved through the physical connection of the volume pot to the chassis, so a loose mounting nut or corrosion could cause the volume to be not completely muted.

vinyl

Is it possible for you that tell me which circuit or parts must be checked for volume problem...
I appereciate you if send me some pictures from testing parts :)


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Post subject: Re: fender super reverb silver face hum problem
Posted: Sun Nov 16, 2014 2:55 am
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Parts to check ; Volumes pots .
No picture available . Look with google ; "how to check pots


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