Curing ticking vibrato with old tube (Fender DR)

[Dan Theman]

Tried to fix the tremolo ticking in my Deluxe Reverb 71 by adding a cap from bulb to ground but without much success. It took away the sharp ticking just a little but still very annoying. Also tried to move around cables but it didn't make any difference. Then I replaced the 12AX7 with an old (and weak) 12AT7 (A Valvo ECC81) and voilà - the tick is gone! And the vibrato still works fine.

 

[RedRock]

I'm glad your solution worked.



There's a Fender service bulletin on this from way back.

The official Fender solution (Service Bulletin number 9)
"The ticking caused by the Vibrato is caused by improper lead dress.

It can almost be "cured" by connecting a .01 mfd 600 volt mylar capacitor
on the 10 meg ohm resistor in the vibrato circuit. this resistor is located
on the parts panel. Remove capacitor across the 10 meg ohm resistor (old
modification) if in place."

(That is, run the cap from the junction of the 10 meg resistor and the
optoisolator to ground.)

"If this does not produce the desired results, then the leads should be
dressed as follows and excessive lengths shortened.

1. Dress the leads to the vibrato speed and intensity controls away from
the tone controls and filter leads.

2. "Bunch" the leads to the components on the parts panel which connect to
the tube socket of the 7025 (12AX7) vibrato tube.

 

[Dan Theman]

I'm glad your solution worked.



There's a Fender service bulletin on this from way back.

The official Fender solution (Service Bulletin number 9)
"The ticking caused by the Vibrato is caused by improper lead dress.

It can almost be "cured" by connecting a .01 mfd 600 volt mylar capacitor
on the 10 meg ohm resistor in the vibrato circuit. this resistor is located
on the parts panel. Remove capacitor across the 10 meg ohm resistor (old
modification) if in place."

(That is, run the cap from the junction of the 10 meg resistor and the
optoisolator to ground.)

"If this does not produce the desired results, then the leads should be
dressed as follows and excessive lengths shortened.

1. Dress the leads to the vibrato speed and intensity controls away from
the tone controls and filter leads.

2. "Bunch" the leads to the components on the parts panel which connect to
the tube socket of the 7025 (12AX7) vibrato tube.

Yes, those are the things I tried with no result.

 

[Johnny Cache]

Yes, those are the things I tried with no result.

Try a higher value cap.

 

[Dan Theman]

Try a higher value cap.

Why? As I wrote, I fixed it with a 12AT7 tube...

 

[Johnny Cache]

Why? As I wrote, I fixed it with a 12AT7 tube...

That's not really a fix. But what the heck if it worked and your happy why not.

 

[RedRock]

What's the definition of a fix?

You could say that it is a return to working order.

 

[Mr. Lumbergh]

I was getting ticking out of the trem circuit on my Lafayette. Not a Fender I know, but uses a similar "bias wiggle" trem. What worked for me was plugging in a footswitch; it seems that there is a disconnect in the jack that takes the trem circuit out when disengaged, but a corroded jack won't isolate it completely.
Worth a shot.

 

[Dan Theman]

That's not really a fix. But what the heck if it worked and your happy why not.

Isn't it? It fixed the problem (the other advices in Fender's solution didn't).
So?

 

[milocj]

I would say that it's "fixed" if the problem no longer exists, however, I would try a different 12AX7 in there to see if you had a bad tube or if the lower gain is what made the problem go away. If you go to a tube with even lower gain you will eventually get to a low enough level of gain to prevent the trem from starting up at all. This would define being completely fixed vs having found a workaround solution that stopped the problem.

I had a '66 Bandmaster that had the same problem start after owning it for 10 years and simply swapping a different tube for the original RCA fixed the tick. I assumed the tube had started to go bad, but it worked fine even as a first gain stage in other amps so I popped it back in and it was fine in the Bandmaster tremolo position again. My guess is that mine simply got some oxidation on the pins/socket and swapping tubes cleaned it off the pin or the socket.

Since it now seems to work properly, I would shoot the pins of the original tube with some contact cleaner or Deoxit and try the original tube again, or pop another tube of the original type into the slot to see if the problem is completely gone (really "fixed") or if it's the lower gain that made the tick go away...simply out of curiosity. It would also give you a hint as to whether the tube you pulled is going bad.

 

[Dan Theman]

I would say that it's "fixed" if the problem no longer exists, however, I would try a different 12AX7 in there to see if you had a bad tube or if the lower gain is what made the problem go away. If you go to a tube with even lower gain you will eventually get to a low enough level of gain to prevent the trem from starting up at all. This would define being completely fixed vs having found a workaround solution that stopped the problem.

I had a '66 Bandmaster that had the same problem start after owning it for 10 years and simply swapping a different tube for the original RCA fixed the tick. I assumed the tube had started to go bad, but it worked fine even as a first gain stage in other amps so I popped it back in and it was fine in the Bandmaster tremolo position again. My guess is that mine simply got some oxidation on the pins/socket and swapping tubes cleaned it off the pin or the socket.

Since it now seems to work properly, I would shoot the pins of the original tube with some contact cleaner or Deoxit and try the original tube again, or pop another tube of the original type into the slot to see if the problem is completely gone (really "fixed") or if it's the lower gain that made the tick go away...simply out of curiosity. It would also give you a hint as to whether the tube you pulled is going bad.

I tried different 12AX7's, brand new JJ and Tung Sol as well as NOS RCA and some old and weak ones. Ticking was there regardless of which tube I used. Only when I changed to the 12AT7 it stopped.

 

[backline]

Yes, those are the things I tried with no result.

Are you 100% sure.?
I do not think I have ever worked on a BF/SF Fender where lead dress of the Trem and PI tubes did not fix the "cross-talk" problem.
good luck

 

[Dan Theman]

Are you 100% sure.?
I do not think I have ever worked on a BF/SF Fender where lead dress of the Trem and PI tubes did not fix the "cross-talk" problem.
good luck

Moved the cables around but nothing happened. For sure, I could perhaps move them more but then I tested with the 12AT7 tube and the ticking was gone.

 

[backline]

Moved the cables around but nothing happened. For sure, I could perhaps move them more but then I tested with the 12AT7 tube and the ticking was gone.

What can you say.? .....hard to argue with success.
Makes me wonder about the components in the circuit...especially the cathode and plate parts.
good luck.....very nice amps

 

[Dan Theman]

Makes me wonder about the components in the circuit...especially the cathode and plate parts.

What are you wondering about? I'm not a tech.

 

[backline]

Just wondering how old they are...their drifted value(s) and if that amp has had a cap job...especially the cathode Elytics.
You could try renewing the cap and resistor for your Trem Tube and see if that gives you any relief. Not usually the cause of this, but if those parts are old/original, they are do for changing anyway.

 

[Dan Theman]

Just wondering how old they are...their drifted value(s) and if that amp has had a cap job...especially the cathode Elytics.
You could try renewing the cap and resistor for your Trem Tube and see if that gives you any relief. Not usually the cause of this, but if those parts are old/original, they are do for changing anyway.

All the e-caps have been changed recently + plate resistors. And now it's quiet so I'm happy with it.