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Post subject: Re: Fender 75 thoughts and Biasing
Posted: Sun May 12, 2013 8:11 am
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I also found 3 bad solder joints.

One is going from the treble pot into the first .1uF 630v cap.

The second solder joints connects from a filter cap, the reverb and the plate 1 pin of the reverb send 12AT7 tube.

And the third one is from the pedal to one of the legs on a Vactec E Vactrol Cell..

They aint broke. They wiggle a little, but they work.
Does that have anything to do with the tone or any extra noise?


Last edited by Feelyfeels on Sun May 12, 2013 8:13 am, edited 1 time in total.

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Post subject: Re: Fender 75 thoughts and Biasing
Posted: Sun May 12, 2013 8:13 am
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Feelyfeels wrote:
I also found 3 bad solder joints.

One is going from the treble pot into the first .1uF 630v resistor.

The second solder joints connects from a filter cap, the reverb and the plate 1 pin of the reverb send 12AT7 tube.

And the third one is from the pedal to one of the legs on a Vactec E Vactrol Cell..

They aint broke. They wiggle a little, but they work.
Does that have anything to do with the tone or any extra noise?


Most definitely. All bad solder joints should be fixed as they are found.

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Post subject: Re: Fender 75 thoughts and Biasing
Posted: Sun May 12, 2013 11:12 am
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I did it and it made a huge difference in buzz.
I cant tell how it changed the sound.
Great fix!


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Post subject: Re: Fender 75 thoughts and Biasing
Posted: Sun May 12, 2013 12:41 pm
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Not having noise on top of the signal is certainly an improvement in tone. :wink:

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Post subject: Re: Fender 75 thoughts and Biasing
Posted: Sun May 12, 2013 1:21 pm
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bluesky636 wrote:
Not having noise on top of the signal is certainly an improvement in tone. :wink:


Oh well.
Guess youre right. :wink:

The thing that is causing the absurd amount of noise and frying bacon sound is the V2 tube.

I pulled every tube one by one and the noise stopped when i pulled the second one.


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Post subject: Re: Fender 75 thoughts and Biasing
Posted: Sun May 12, 2013 3:43 pm
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Feelyfeels wrote:
bluesky636 wrote:
Not having noise on top of the signal is certainly an improvement in tone. :wink:


Oh well.
Guess youre right. :wink:

The thing that is causing the absurd amount of noise and frying bacon sound is the V2 tube.

I pulled every tube one by one and the noise stopped when i pulled the second one.


Did you put a known good tube back in it's place? If not, keep in mind that V2A is the reverb recovery tube and is fed by V3A and V2B is part of the circuit fed by V1B. It could be the tube or somewhere in one of those two circuits.

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Post subject: Re: Fender 75 thoughts and Biasing
Posted: Sun May 12, 2013 5:15 pm
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Quote:
Did you put a known good tube back in it's place?


The tube is working, its a new Tung-Sol 12AX7.
Forgot to say that its only when i remove the V2 out of the chain the noise stops.

Bad plate resistors?


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Post subject: Re: Fender 75 thoughts and Biasing
Posted: Sun May 12, 2013 6:57 pm
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Feelyfeels wrote:
Quote:
Did you put a known good tube back in it's place?


The tube is working, its a new Tung-Sol 12AX7.
Forgot to say that its only when i remove the V2 out of the chain the noise stops.

Bad plate resistors?


Could be, but you need to check both circuits that use V2.

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Post subject: Re: Fender 75 thoughts and Biasing
Posted: Mon May 13, 2013 10:59 am
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I spent a whole day doing:
*Shortening every cable and all the wires so they fit perfect.
*Anti-oxide all the pots again.
*Biased the tubes.
*Fixed every loose solder joints.
*Changed out some the first caps in the circuit higher values.
*Removed the mid boost and the bright switch's function.
*Rewired the lead control so it affects the clean channel (since i am not using the "drive" channel)
*Shaking my head in frustration a thousand times for the previous guys "work".
*Burnt my hands a million times while soldering.

The amp got 80% quieter and the tone compares with a Deluxe Reverb i tested for not so long ago.

It stills weighs a ton. But i can deal with that if i get that tone.

Thanks for all the help again, man! I really appreciate it.


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Post subject: Re: Fender 75 thoughts and Biasing
Posted: Mon May 13, 2013 4:55 pm
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Excellent! :mrgreen:

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