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Post subject: Fender Twin 65 Reissue concern
Posted: Sun Apr 14, 2013 7:10 pm
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Hi everyone,

Just purchase my twin recently.

Simply put - this amp is unbelievable in its tone, headroom and everything else.

Its not brand new, so when I tested it first I have noticed a bit of noise regarding the Reverb pot. Its not unbearable, but I would like to fix it.

Here is the problem:

Reverb Volume 0 - very little to no noise at all

Reverb volume 2 - the noise is there, more then on Vol 0

Reverb volume increase - the more the Reverb volume goes up, more hum is noticeable

I usually go to Vol 2 or 1.5 on Reverb

I have completely disconnected the Reverb unit from the amp - no difference, the hum is still there, and increases with Reverb Vol increase.


Any ideas as to what to do?

Many thanks!

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Post subject: Re: Fender Twin 65 Reissue concern
Posted: Mon Apr 15, 2013 2:37 am
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First , try new tubes on Reverb Stage. V3 12AT7 and V4 12AX7
Tube number see from the back of the amp ; right to left ; V1, V2 .......

Which Twin it is ? Year , This one maybe ? 65 Reissue ?

http://www.fender.com/en-CA/series/vint ... in-reverb/


Schematic ;

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


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Post subject: Re: Fender Twin 65 Reissue concern
Posted: Mon Apr 15, 2013 5:19 am
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Its 65 re-issue built in 2002 or thereabout.

Will give it a go ...


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Post subject: Re: Fender Twin 65 Reissue concern
Posted: Mon Apr 15, 2013 5:47 am
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Nikola Tesla wrote:
Its 65 re-issue built in 2002 or thereabout.

Will give it a go ...


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Sur itis a 65 reissue, you write in the title , Sorry


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Post subject: Re: Fender Twin 65 Reissue concern
Posted: Mon Apr 15, 2013 10:28 pm
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Any other suggestions guys, thanks.

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Post subject: Re: Fender Twin 65 Reissue concern
Posted: Mon Apr 15, 2013 10:50 pm
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You can get rid of most unwanted reverb hiss/hum noise by replacing stock reverb cables with good quality ones. I did this and the Hiss has been nicely reduced.

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Post subject: Re: Fender Twin 65 Reissue concern
Posted: Tue Apr 16, 2013 1:17 am
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AaronK wrote:
You can get rid of most unwanted reverb hiss/hum noise by replacing stock reverb cables with good quality ones. I did this and the Hiss has been nicely reduced.




No difference even when I disconnect the reverb tank and remove it from the amp. The hum is still there, its minimal when reverb pot is at zero, and gets louder (the his) when the reverb pot goes up.

Any further thoughts?


:?:


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Post subject: Re: Fender Twin 65 Reissue concern
Posted: Tue Apr 16, 2013 1:59 am
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Nikola Tesla wrote:
Any other suggestions guys, thanks.

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Are you kidding ?
And what about my answer ? The first you receive ?

With ( defective ) tubes and open reverb circuit ( no thank ) act like an antenna and you must have noise.

Tubes , tubes ,tubes.........


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Post subject: Re: Fender Twin 65 Reissue concern
Posted: Tue Apr 16, 2013 2:08 am
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Thank you stratele52, I'm about to buy the tubes (V3 & V4) and try if that helps .. just a bit inpatient to solve the issue.


Cheers!

:D


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Post subject: Re: Fender Twin 65 Reissue concern
Posted: Tue Apr 16, 2013 2:12 am
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The only other thing it could be is iether bad grounding/shielding on the recovery valve circuit leading up to the reverb pot, or there is a noisy wire in close proximity to the reverb recovery circuit and pot.

Try this, with the reverb tank unplugged and reverb volume at 3 (don't want to make a loud pop), short the return cable centre pin to it's shield and see if the noise goes away. If you do not know which is the return cable - it should be the one that is connected to the OUT of the reverb tank. If the noise does not get reduced then the problem exists with possibly the Recovery valve or the smoothing capacitors on the DC supply to the valve or bad grounding/shielding between valve and pot.

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Post subject: Re: Fender Twin 65 Reissue concern
Posted: Tue Apr 16, 2013 7:26 pm
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Probably V3 or V4 tube as stated above. Let us know how you make out.


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Post subject: Re: Fender Twin 65 Reissue concern
Posted: Wed Apr 17, 2013 11:43 pm
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/


$55.00 later with both V3/4 new tubes installed no difference whatsoever.


Also, with reverb pot on 10 and guitar cable disconnected, there is some feedback, that starts quietly and then increase.

Where the hell the feedback is coming from?!?



:?



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Post subject: Re: Fender Twin 65 Reissue concern
Posted: Thu Apr 18, 2013 5:58 am
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I just copied and pasted my response from another thread:

----------------------------------------------------------------------------------
I have found the cure to my reverb feedback issue i.e. when the reverb knob was turned passed 5 it would slowly build up with a high pitch feedback even when all other knobs were right down (This seems to occur on a variety of amps with reverb tanks) . I have been paying close attention to everyone elses issues and attempts at fixing it, and after doing some comparisons with tubes/cables and various unplugged reverb combinations, adding foam padding, someone suggested in a forum that their reverb might be microphonic. Whether a reverb tank can be microphonic in itself I cannot tell you, but it made me want to take a closer look at the physical reverb circuit to rule out any possible cause.

Looking on Accutronics website they suggest that the orientation that Fender has chosen for the SS and other combo Amp reverb tanks is the least desirable, as this causes gravity to act on the reverb spring and push the ferite beads (there are 4 in mine - one on each end of each spring) in the transformer to sit real close to one side and not dead centre as intended. Now does this make it more sensitive, possibly as smaller movements will be detected easier but bigger ones will be constrained physicaly. Accutronics also state that they custom set the position of these beads based on the customers mounting requirements.

So I took a close look at mine and after a long hard check and fiddle I found that one bead was sitting way too close to the reverb transformer plate, and with gravity added it was REALLY close. So I decided to adjust it and found that you can't bend or solder it into its correct position as that would be too risky. I eventualy found that with some small pliers I could rotate the copper stud that holds this bead and spring until it was orientated such that gravity pulls this bead more central. I then put a dab of superglue on the copper stud to hold it from rotating back.

I am pleased to say that I tested it last night at full reverb volume and while before it would feedback instantly and consistantly at even a 5 setting, I could not get it to feedback at all even at 10.

Other improvements I made while I was trying to fix my reverb was:
- added good foam padding under reverb unit to dampen any vibrational shock in the CAB (this did not cure my feedback, but will help dampen unwanted CAB vibrations).
- the 4 floating springs that stabilize the reverb carridge in it's housing would creek and snap at their fastening rings when moved, giving the reverb a sharp unpleasant jolt of sound, so I put a dab of superglue on each of the fastening rings either side of each spring to ensure only the springs move between their fastenings, making the dampening much smoother.

---------------------------------------------------------
To follow up I have not yet had any more Reverb feedback, and I have played a Gig and 2 practices since fixing it. So I am certain it is fixed.

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