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Post subject: Fender Twin Noisy
Posted: Thu Sep 18, 2014 10:26 am
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Hey People,
I have a customers Twin with the Ser# LO682308.
Can't find the code on the Fender Site for dateing....but I know it's recent!
Mainly just curious about the date.
The problem is the amp works great but has one hell of a hum.
I tested the tubes..all good. Then I tapped the 12AT7 next to
the power tubes and it was very noisy when tapped. I then tapped the 12AX7
and it was extremely more noisy.
Next I tested the plate voltage on the 12AX7's plate pin and it made more noise
when I touched it with my test probes..
Any ideas?
Thanks folks!
tube dude


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Post subject: Re: Fender Twin Noisy
Posted: Fri Sep 19, 2014 2:02 am
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Joined: Fri Feb 05, 2010 4:31 am
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Location: Province de Québec, Canada
How do you test tubes ? Tube tester can't test amps tubes, shure you know that .
You need to put knew good tubes

Wich Twin ? reissue , Black face .Recent is a reissue ?

Test must be do with nothing plug in the amp , amp alone

Hum ; Bad / unmatched 6L6's , bad contacts on tubes socket , filter caps, bad ground.

1- Remove phase inverter tube , still hum ? If yes look next tubes and circuits ; 6L6
No hum; trouble is before this tube .

2- Do same test with each other tube; you'll see where hum is coming


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Post subject: Re: Fender Twin Noisy
Posted: Fri Sep 19, 2014 2:14 am
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Location: Province de Québec, Canada
94 Twin amp shematic here ;

http://support.fender.com/schematics/gu ... ematic.pdf

Some twins here;

http://ampwares.com/?brand=fender&line=twin

It is a Twin not Twin reverb ?


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Post subject: Re: Fender Twin Noisy
Posted: Fri Sep 19, 2014 10:13 am
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Well the tube tester I use is a TV7/DU.
So far it hasn't let me down.
I did all sorts of tube swaps and it made no difference.
Pre amp and power.
If this is an open ground this may take a while.
Like I had said V7 and V8 are noisy when touched. V7(12AX7)
being the noisiest.
Oh well venture on I suppose!
Thanks
tube dude


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Post subject: Re: Fender Twin Noisy
Posted: Fri Sep 19, 2014 10:48 am
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Location: South Carolina, USA
Sounds like to me you've tried pretty much everything I can think of, what was the bias reading?


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Post subject: Re: Fender Twin Noisy
Posted: Fri Sep 19, 2014 10:57 am
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tube dude wrote:
Well the tube tester I use is a TV7/DU.
So far it hasn't let me down.
You are very lucky ,or you did not test tube often .Remember what I said

I did all sorts of tube swaps and it made no difference.
Pre amp and power.
If this is an open ground this may take a while.

Like I had said V7 and V8 are noisy when touched. V7(12AX7)
being the noisiest.
You put new tubes at V7 and V8 and they are noisy too ???

Oh well venture on I suppose!
Thanks
tube dude


Do the trouble shooting I suggest step by step and report


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Post subject: Re: Fender Twin Noisy
Posted: Sat Sep 20, 2014 4:15 am
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stratele52, Relic G Man,
I really appreciate your contacting me.
Here is what I found...First off this amp is like brand new.
Kept in a case and very well taken care of.
I kept checking and tapping the 12AT7 and AX7, checking all the wires and board connections for those tubes. Also checked all the others and cleaned them.
Then I pushed slightly on the AX7 and it stopped the noise.
I removed the tubes and cleaned and tightened the terminals
of the sockets..All is great.
Like I said above thanks so much for your input.
Take care guys!
tube dude


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Post subject: Re: Fender Twin Noisy
Posted: Sat Sep 20, 2014 4:20 am
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Joined: Fri Feb 05, 2010 4:31 am
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Location: Province de Québec, Canada
:D


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Post subject: Re: Fender Twin Noisy
Posted: Sat Sep 20, 2014 2:23 pm
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Cool!!!


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