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Post subject: 1964 Concert Tremolo is Too Fast
Posted: Mon Jun 03, 2013 7:56 pm
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Roadie
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Recently I noticed the tremolo on my 64' Concert is way too fast, even with the speed dial on 1. It used to be much slower. Can someone explain what component(s) control the speed-tube, cap or resistor. It's stock except for sprague atom ecaps. I did the cap job over a year ago and it sounded fine. Thanks.


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Post subject: Re: 1964 Concert Tremolo is Too Fast
Posted: Mon Jun 03, 2013 8:56 pm
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http://ampwares.com/schematics/concert_aa763.pdf

Try a new tube. Check the speed pot, the surrounding resistors and caps to be sure the components are within tolerance.

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Post subject: Re: 1964 Concert Tremolo is Too Fast
Posted: Mon Jun 03, 2013 9:23 pm
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bluesky636 wrote:
http://ampwares.com/schematics/concert_aa763.pdf

Try a new tube. Check the speed pot, the surrounding resistors and caps to be sure the components are within tolerance.


+1

The trem roach might also be heading south towards its final "vacation" destination.

Arjay

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Post subject: Re: 1964 Concert Tremolo is Too Fast
Posted: Tue Jun 04, 2013 6:25 am
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Roadie
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I replaced the filter and preamp caps not long ago. I'll check the resistors. When I crank up the intensity, the tube went south-old sovtek WA. I replaced the bias resistor-on the bias board-with a 25uf/100. It made the amp hum a bit. I bumped it up to a 50uf/100 and she's quiet. The schematic calls for a 25uf/50, but that seems small. Would ya'll go with the 50uf normally as a replacement? I wouldn't think that would affect the tremolo speed.


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Post subject: Re: 1964 Concert Tremolo is Too Fast
Posted: Tue Jun 04, 2013 7:23 am
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A 25ufd bias "resistor"......?

:wink:

Arjay

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Post subject: Re: 1964 Concert Tremolo is Too Fast
Posted: Tue Jun 04, 2013 10:07 am
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Roadie
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Capacitor. :mrgreen:


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Post subject: Re: 1964 Concert Tremolo is Too Fast
Posted: Tue Jun 04, 2013 12:06 pm
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Roadie
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Retroverbial wrote:
bluesky636 wrote:
http://ampwares.com/schematics/concert_aa763.pdf

Try a new tube. Check the speed pot, the surrounding resistors and caps to be sure the components are within tolerance.


+1

The trem roach might also be heading south towards its final "vacation" destination.

Arjay


I'm heading to my vacation destination-beach house in NC. I can serenade the sunbathers with my old strat and super reverb.
To answer my own question about the bias cap, it is 50uf/50V stock. Fender has it listed as 25uf/50v on the schematic. Can you trust any Fender schematic? I replaced the vibrato cap with a 25uf/50v-25/25 on the schematic. I never saw the original cap, so I'm not sure about the actual value. Does anyone know the actual value the vibrato cap on a 64' Concert amp?


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Post subject: Re: 1964 Concert Tremolo is Too Fast
Posted: Tue Jun 04, 2013 8:00 pm
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Krank, the 25uf/25vdc would be the usual cathode bypass cap for the 12AX7. The oscillation of the vib tube is determined by the .01uf(2) and the .02 capacitors. These guys along with the speed control set-up the response time, that wiggles the pre amp signal to ground. A working 12AX7 and a decent LDR, should round out the deal. JMO, Art

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Post subject: Re: 1964 Concert Tremolo is Too Fast
Posted: Wed Jun 05, 2013 3:47 am
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Krankster, see the three ceramic disc caps (0.02, 0.01, 0.01) running in a row, perpendicular from the third 12AX7 (from Right of layout)? Other two are labeled 7025, in this schematic.

http://ampwares.com/schematics/concert_aa763.pdf

Someone could have replaced of the 0.01mfd with a 0.02 mfd. Or running all three 0.02 mfd. This will REALLY slow the vibrato to a near stand-still. If this is so, replaec with OEM 0.02, 0.01, & 0.01 mfd caps. Maintain proper order!

Those are the caps that control the time-constant/phase shift of your tremolo (vibrato) circuit. When these caps goes outta spec your vibrato will act real funky.

Get one 0.02mfd/1KV+ and two 0.01mfd/1KV+ rated ceramic cap and try replacing the OEM ones. The higher the voltage rating, the better. US made, even better.

Then, a good idea is to change the 12AX7 cathode bypass caps OEM = 25mfd/25VDC with fresh 25mfd/50VDC rated Sprague Atoms. This will help pass more mA and raise the idle bias of the 12AX7. This really can help EFX circuits (like tremolo and reverb).

Rotate tubes around. And clean the sockets and pins -- -and you should be in business, If not... suspect the opto-coupler roach.


Good luck! :mrgreen:

EDIT: DIDN'T SEE ART'S POST... SORRY


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Post subject: Re: 1964 Concert Tremolo is Too Fast
Posted: Wed Jun 05, 2013 11:33 am
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Thanks fellas. I'm learning that what's on paper and what is in Fender amps is often not the same. All the caps are original and correct-beautiful site. I'm getting some NOS 12ax7's in a few days and will see if that's the problem. A Sprague Atom 25@50 was installed within the last year. The roach looks original-smoked even-that's suspect. This amp covers all of the bases-clear Fender to Marshall crunch. I just got a new cell phone and will post pics.


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Post subject: Re: 1964 Concert Tremolo is Too Fast
Posted: Wed Jun 05, 2013 2:30 pm
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Krankster wrote:
I'm learning that what's on paper and what is in Fender amps is often not the same.


Some of us have been aware of this for decades.

:mrgreen:

Arjay

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Post subject: Re: 1964 Concert Tremolo is Too Fast
Posted: Sat Jul 06, 2013 1:43 pm
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Roadie
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[img]C:\Users\Chris\Pictures\1964%20Concert%20Chassis.jpg[/img]


Last edited by Krankster on Tue Jul 09, 2013 10:49 am, edited 1 time in total.

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Post subject: Re: 1964 Concert Tremolo is Too Fast
Posted: Sat Jul 06, 2013 1:44 pm
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Roadie
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Post subject: Re: 1964 Concert Tremolo is Too Fast
Posted: Sat Jul 06, 2013 8:06 pm
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Krankster wrote:
Image


No go... on the images.

:(


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Post subject: Re: 1964 Concert Tremolo is Too Fast
Posted: Wed Jul 10, 2013 9:56 am
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