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Post subject: Fender 68 Custom Twin Reverb Schematic
Posted: Sat Nov 12, 2016 9:09 pm
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I have been searching, but no luck yet. Does anyone have the schematic to this thing?

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Post subject: Re: Fender 68 Custom Twin Reverb Schematic
Posted: Sun Nov 13, 2016 4:40 am
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I ask to Fender few months ago. They answer me there is no schematic ready yet.

:(

Hi,

We currently do not have an available schematic for that amplifier. The techs have yet to make a "scrubbed" version of the schematic for this amplifier. I'm not sure if it will be available in the near future either.

Regards-

Chase Miller

Representative, Consumer Relations /U.S. Direct
Sales

Fender Musical Instruments Corp.
17600 N. Perimeter Drive, Suite 100

Scottsdale, AZ 85255

Telephone: 480-845-5131

Fax: 480-367-5262


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Post subject: Re: Fender 68 Custom Twin Reverb Schematic
Posted: Sun Nov 13, 2016 7:58 am
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Thanks for the response..

Maybe someone knows which resistor is the NFB resistor for this amp.. I found a couple of mod's for the 68 CDR amp..

I would really like to try it on the 68 CTR before I gut it for a kit.. If it will lower the noise floor to an acceptable level that would be a good thing.. I am using an attenuator now and it helps quite a bit..

Image

_________________
In the hands of the right people it can change the world. Not bad for a hunk of ash, a few magnets, and some wire.
Band Site
http://www.reverbnation.com/bigskybluesband
Demos
http://www.youtube.com/user/bigskybluesband


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Post subject: Re: Fender 68 Custom Twin Reverb Schematic
Posted: Sun Nov 13, 2016 8:24 am
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Location: Province de Québec, Canada
NFB resistor is to have more clean output, not for the noise.
More powerful is the amp more noise you may hear.
If you use power attenuator it is because you crank the amp= more noise.

Try low gain tube in V1, V2.......

I use 12AY7 with success in high gain amp.

There are many complain about noise in new Fender amps


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Post subject: Re: Fender 68 Custom Twin Reverb Schematic
Posted: Sun Nov 13, 2016 8:58 am
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Aspiring Musician
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I am using 12AY7's in all five of my high wattage Fender tube amps, works great.. I left the 65 DRRI I have stock, it just works good in my ears stock..

This CTR is the pisser though, I have tried a tube fix with that thing to no avail.. The only thing that has dropped the hiss in that thing is attenuation or cutting the beatch off..

_________________
In the hands of the right people it can change the world. Not bad for a hunk of ash, a few magnets, and some wire.
Band Site
http://www.reverbnation.com/bigskybluesband
Demos
http://www.youtube.com/user/bigskybluesband


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Post subject: Re: Fender 68 Custom Twin Reverb Schematic
Posted: Sun Nov 13, 2016 9:33 am
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Here is the PCB layout..

Image

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In the hands of the right people it can change the world. Not bad for a hunk of ash, a few magnets, and some wire.
Band Site
http://www.reverbnation.com/bigskybluesband
Demos
http://www.youtube.com/user/bigskybluesband


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Profile
Post subject: Re: Fender 68 Custom Twin Reverb Schematic
Posted: Mon Nov 14, 2016 8:44 am
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You maybe able to trace the path to the GNFB resistor. It is connected to one lead of secondary of the output tranny. Fender usually taps this on the speaker output jack (back of chassis). Then, follow the lead from the jack to the circuit board. The first component is USUALLY the GNFB resistor.

Photo from brownface era amp. I have no good close-up of any reissued Fender amp's speaker jacks. The tap is the yellow wire. Green and black are the output tranny's secondary leads.

Image


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Post subject: Re: Fender 68 Custom Twin Reverb Schematic
Posted: Sun Jan 08, 2017 9:01 am
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If anyone else out there wants to tame the idle hiss in this amp, possibly the other 68 Custom line also, I use a Weber Mass Lite 100w Attenuator. It makes it a lot more playable in my ears...

I do not dime my 68 Custom Twin Reverb, I usually have it set on around 5 or 6 on the Custom side and the Vintage is around 4 or 5. I plug the guitar into the Custom number one input and daisy chain from the Custom two input to the Vintage one input.

Then you can clamp down the attenuator to take out the idle hiss. If I am jamming live I find that the idle hiss is a lot less noticeable, so I usually turn the amp down a little and apply less attenuation or switch it off.

I could probably install some less efficient speakers in this thing and get the same result.

_________________
In the hands of the right people it can change the world. Not bad for a hunk of ash, a few magnets, and some wire.
Band Site
http://www.reverbnation.com/bigskybluesband
Demos
http://www.youtube.com/user/bigskybluesband


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Post subject: Re: Fender 68 Custom Twin Reverb Schematic
Posted: Wed Dec 18, 2019 3:06 pm
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Regarding the '68 Custom Twin Reverb noise issue(s)

If you want to lower the noise floor hiss, a simple fix is to change V4 tube (4th from the right looking at the back) from the stock 12AX7 to a 12AY7 low gain tube.

They say this will change the characteristic of the amp, as it is meant to be a high gain amp, though going with a lower gain tube on the reverb output, we find that it simply lowers the amount of overall reverb, yet usually you would only have your reverb at 2 or 3; with a 12AY7 you may want to turn your reverb to 3 or 4.

Have fun


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Post subject: Re: Fender 68 Custom Twin Reverb Schematic
Posted: Sat Dec 21, 2019 8:37 am
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I finally fixed this amp and it sounds really good now. I took out the new 68 Custom chassis and stuck a 1981 ultralinear 135 watt Twin Reverb chassis in the 68 Custom Twin Reverb cab, it is one of the blackface ones, but it is a silverface amp. Sounds awesome but heavy as hell once I switched the speakers out with an Eminence Swamp Thang and a Eminence Texas Heat. Silent as mouse on idle, but will take the paint off of a car cranked up..

The 81 chassis fit perfect in that 68 Custom cab.. The guy I bought the 81 chassis from wanted my 68 custom chassis, so I ended up paying around $30.00 for the swap, plus the speakers.

_________________
In the hands of the right people it can change the world. Not bad for a hunk of ash, a few magnets, and some wire.
Band Site
http://www.reverbnation.com/bigskybluesband
Demos
http://www.youtube.com/user/bigskybluesband


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Profile
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