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Post subject: Re: Vibrato Pop Pop Pop sound?
Posted: Fri Aug 09, 2013 8:18 am
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The fix is complete, and the pop pop pop is gone, and the amp is considerably quieter.

Replaced the 12AX7 in V3 with a Sovtek 12AX7-WA
Replaced the 25 microfarad, 25 Volt axial capacitor in the oscillator circuit (Sprague)
Replaced one of the 0.01 microfarad, 440v capacitors (went up to 630v, mylar)

Resoldered the sockets and the pots.

Seems good to my tone deaf ears.





Sorry for the intrusion but mine put put's and it speeds up and slows down as I change the speed control when I use the vibrato. My Amp is a 69 SFSR Im am sure it is a AA1069, I am very bad a reading schematics I can change parts though. I am sorry to ask but is there any way to point out where the 25/25 cap ( I just dont know where the oscillator circuit is) and the 0.01 microfarad, 440v capacitor is located in the layout, I believe the bandmaster and a SR have similar layout and I could be so wrong with this thought
Thank You
Mud


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Post subject: Re: Vibrato Pop Pop Pop sound?
Posted: Sat Aug 10, 2013 1:20 pm
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Mud, here are the before and after photos of the circuit and the repair.

I didn't do the work myself, it was done in a shop. I suggest that you have someone trouble shoot the whole circuit rather than randomly replacing parts. As you can see from the thread...there were lots of possible problems/fixes.

Also, I see that the 0.01uF capacitor was an add-on...not a replacement.
Hope this helps

Image

Image

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Post subject: Re: Vibrato Pop Pop Pop sound?
Posted: Sat Aug 10, 2013 4:16 pm
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I believe that 0.01 mfd added cap in a "last-ditch" fix recommended by Fender to fix the tick-tick tremolo issue. It goes between the 10Meg-ohm (brown-black-blue) resistor to a ground point --- bifurcating the circuit at this point. Making a three way connection between the anode plates of the 12AT7 and ground.


This resistor is just left of the opto-roach on the schematic. Tone will change in the circuit --- as this fix changes the time-constant of that part of the circuit. But, it's better than that annoying ticking.

Arjay: you still have a copy of the original Fender Tech Note concenring this issue?

http://www.webphix.com/schematic%20heav ... _schem.pdf

http://www.regiscoyne.com/tech/tremolo/


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Post subject: Re: Vibrato Pop Pop Pop sound?
Posted: Sat Aug 10, 2013 6:03 pm
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I believe these two tips from Regis were the gist of Fender's TSB regarding the trem-tick issue......

•Funny ground on some SF Fenders; On one of the signal tubes, the cathode cap was placed on the tube socket, and wired to a ground lug on the vibrato cancel jack instead of across the resistor on the fiberboard. The vibrato shares this ground line, and can the vibrato current can cause audible ticking in the audio path. Rewire the cap to another ground or relocate it to the board.

•Poor Signal wire layout: signal wires run too close to vibrato leads can pick up the LFO signal. Move them around and see if the ticking goes away.

His other suggestions about the trem circuit are worth looking into as well, especially the switchable mod to take the oscillator completely out of the circuit.

Arjay

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Post subject: Re: Vibrato Pop Pop Pop sound?
Posted: Mon Aug 12, 2013 5:37 am
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Thanks, I did not mean to High Jack the thread. Worked all weekend long hours, back in the office today, not sure when I will get a chance to follow all of your very kind suggestions, as the nature of the business I am in ( audio engineer) has got me seeing my bed and home maybe 6 to 7 hour for a few weeks, I will let ya's know the result "further on up the road"
Thank you very kindly
Mud


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