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Post subject: 71 Dual Showman Reverb TFL 5000X circuit
Posted: Fri Dec 31, 2010 4:01 am
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Hello,
i just got a "new" old Fender Dual Showman Reverb and i'd like to revise it's amp and replace broken or wrongly repaired parts. Therefore I'm wondering which circuit this amp has and I'd be thankful for advice where to find schematic and a service manual.

The serial number stamped on the back is A33260 which confirms the production year of 1971.

Trannys part numbers are:

022764
022699
022889
022921

In the chassis a stamp says August #6 1971.
The letter / number # is not readable any more.

Thanks for you help, yours, crec


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Post subject: Re: 71 Dual Showman Reverb TFL 5000X circuit
Posted: Fri Dec 31, 2010 10:21 am
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What makes you suspect the amp has "broken or wrongly repaired parts."?

Is the amp equipped with a master volume control?

If so, does that control have the integral "pull-boost" switch?

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: 71 Dual Showman Reverb TFL 5000X circuit
Posted: Fri Dec 31, 2010 11:19 am
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A potentiometer for channel volume is broken and another one seems to be replaced in a very unprofessional way having a closer look at the soldering, therefore i'd like to check it against a schematic.
Also some resistors and capacitors I measured have changed their value during the time and be better replaced.

The amp has no master volume.

Thanks, crec


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Post subject: Re: 71 Dual Showman Reverb TFL 5000X circuit
Posted: Fri Dec 31, 2010 11:23 am
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I understand now.

This may be the schematic for your amp......

http://web.archive.org/web/200610201037 ... _schem.pdf

Best of luck, HTH

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: 71 Dual Showman Reverb TFL 5000X circuit
Posted: Sat Jan 01, 2011 11:46 am
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Ah this seems to be the best fitting schematic. Thank you very much. After replacing the most differing parts regarding it's original state and correcting the "repairs" of the former owner in a proper way, the amp seems to work again except for a small problem with a defective input jack (1) on normal channel which is meant to be replaced.
Does anybody know where to find a suitable operating manual on the internet?
Thanks for your help,

crec


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Post subject: Re: 71 Dual Showman Reverb TFL 5000X circuit
Posted: Sat Jan 01, 2011 12:54 pm
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Doubtful that few, if any, original "user manuals" survive.

Operating these beasts are pretty straightforward -- what is it you need to know?

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: 71 Dual Showman Reverb TFL 5000X circuit
Posted: Sat Jan 01, 2011 2:04 pm
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I was wondering how to use the 10k pot on chassi for biasing.

Also i'd like to know if the user manual says something about input level and input impedance restrictions.

Thanks, crec


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Post subject: Re: 71 Dual Showman Reverb TFL 5000X circuit
Posted: Sat Jan 01, 2011 3:42 pm
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Look there for better ( clear) schematics and layout
http://www.el34world.com/charts/Schemat ... _AA270.pdf


At www.el34world, you have lots of schem


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Post subject: Re: 71 Dual Showman Reverb TFL 5000X circuit
Posted: Sat Jan 01, 2011 3:55 pm
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No Dual Showman Reverb ever had a true output tube bias adjustment pot. It's actually a "balance" control.

As for input signal levels, it's a guitar amp......what more do you need to know?

You'll be safe with any audio input signal less than 750 millivolts peak-to-peak.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: 71 Dual Showman Reverb TFL 5000X circuit
Posted: Sun Jan 16, 2011 1:26 pm
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Hey Crec,
I know this is a bit of a late response, but I've been away from the forum since it was shut down for updating and just noticed your post. I too am a big fan of the DSR and thanks to a series of wacky misadventures have learned a few things about the history of this model. I'm sure you've discovered that the "X" in TFL 5000X stands for an eXport model, as opposed to the more commonly seen 5000D manufactured for Domestic distribution. I'm not positive, but I don't believe there were any differences in the circuitry for any given year betwixt the domestic and export versions. What is different is that in the early years of its manufacture the DSR went through several circuit changes and "improvements" to the AB763 circuit on which it was (ostensibly) based. Mine is a '68, and originally had the first DSR circuit, designated AA768. This was followed almost immediately by the AA769 revision, and then later by the AA270 revision. Purportedly there was also an AC568 version, but I have not as yet found a schematic that shows a DSReverb with the AC568, though it's possible that it was used for the non-reverb SF Dual Showman. Once Fender started making the "pull boost" and 135W versions things change again and become even more confused.
Installing a tube bias pot in place of the hum balance pot is an easy fix that any competent amp tech should be able to do. At one time mine (somewhat superfluously) had both. You are right to worry about possible tinkering with a nearly 40 year old amp, and having it checked out by a professional is the way to go. The good thing is that these early DSRs are very easy to modify to "Blackface" specs for improved tonality. Kinda windy, I am, but I hope this helps!...O.


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Post subject: Re: 71 Dual Showman Reverb TFL 5000X circuit
Posted: Sun Jan 16, 2011 2:29 pm
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nyquilcoma wrote:
Purportedly there was also an AC568 version, but I have not as yet found a schematic that shows a DSReverb with the AC568, though it's possible that it was used for the non-reverb SF Dual Showman.


Partially correct -- the AB568 circuit revision applied only to the non-reverb Dual Showman chassis and those very few Showman (8-ohm configured) heads that were offered through January of 1969.

HTH

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: 71 Dual Showman Reverb TFL 5000X circuit
Posted: Sun Jan 16, 2011 3:42 pm
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Thanks, Arjay! As ever, I defer to your superior knowledge on the subject of all things Fender-amp related! Happy belated New Year to you, your family and all the good folks on the forum. I've learned a great deal from the members since I discovered this site, and will continue my quest in 2011. Everyone gird up their loins for more of my stupid questions with obvious answers! Cordially yours...O.


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Post subject: Re: 71 Dual Showman Reverb TFL 5000X circuit
Posted: Sun Jan 16, 2011 6:37 pm
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There are no "stupid" questions, NC.

(you might receive a dumber-than-dirt answer, however......)

:mrgreen:

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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