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Post subject: Fender 1976 Vibrolux Silverface (Tube Manufacture??)
Posted: Mon Jan 12, 2009 8:41 pm
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Hi,
I recently acquired a 1976 Silverface Virbrolux Reverb. This is an awesome amp. I have some questions about the preamp tubes. I think the preamp tubes are original, but I could be wrong. The tubes say "Fender special design" in brown/orange writing. The date codes say 76-48 188-5 for the 12ax7a/7025 tubes, and 76-39 188-5 for the 12at7. The tubes also say "USA" on them. I know Fender didn't make tubes, but I was wondering if anyone knows who would have manufactured these tubes?
Do these seem original?

Thanks,
Jason


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Posted: Wed Jan 14, 2009 10:54 am
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I have no clue as to what those numbers might mean but I have to think that on a 33 year old amp its pretty likely they are not original tubes.
Fender is in the tube business as you can see in the link below:




http://www.fender.com/products//search.php?partno=0994020001


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Posted: Wed Jan 14, 2009 7:11 pm
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Actually, depending on how often the amp was used, moved around, turned on and off, as well as the quality of the tube/s all determine how long the preamp tubes will last. It is possible that the tubes are original. Preamp tubes can last for thousands of hours. I have a marshall JCM 800 that is only 5 years newer than my Fender and still has functional original ecc83 preamp tubes in it.
Maybe this is a question for Fender or someone who knows date codes?
Thanks J


Last edited by jgab on Wed Jan 14, 2009 7:18 pm, edited 2 times in total.

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Posted: Wed Jan 14, 2009 7:16 pm
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By the way, these Fender tubes are probably just Fender stamped and manufactured by someone else. Don't be fooled that just because Fender put their name on it that it was manufactured by Fender. Relabeling tubes is a marketing strategy to sell more tubes. Do an internet search on relabeling tubes and you will see what I mean.
J


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Posted: Wed Jan 14, 2009 7:51 pm
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jgab wrote:
By the way, these Fender tubes are probably just Fender stamped and manufactured by someone else. Don't be fooled that just because Fender put their name on it that it was manufactured by Fender. Relabeling tubes is a marketing strategy to sell more tubes. Do an internet search on relabeling tubes and you will see what I mean.
J


I am sure that's exactly what has taken place. They are prolly relabelled Groove Tubes.


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Posted: Thu Jan 15, 2009 12:16 pm
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Hi everybody,
Just remember that a whole lot of amps are kept in closets and never retubed!
Back in the 70's - we never retubed an amp unless it stopped working and tubes were nominally cheaper then.
It is very possible the have a 33, 35 or 50 year old amp with the original tubes still in it -If the amp was not used very much.
I just bought a Fender Pro Reverb amp, that was out of storage, two weeks ago. It is a 1977-78 amp and it has the original tubes in it and it still sounds great!!

Those tubes say USA on them because they were probably made by RCA or Sylvania back when they still made tubes in the good old USA!
The Fender stampings on the tubes would be done by the manufacturer as a part of the large contract that Fender had with said manufacturer back in the 1960s- 70's.

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Posted: Thu Jan 15, 2009 5:17 pm
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Do you know how I could figure out if they were RCA or Sylvania? I suppose I can do a visual comparison, but I am wondering if there was a difference in the way they looked over a certain time period?


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Post subject: Re: Fender 1976 Vibrolux Silverface (Tube Manufacture??)
Posted: Sun Feb 27, 2011 3:10 am
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The 12AX7 tube is a USA made General Electric made in the 48th week of 1976 and the 12AT7 is also the same make and made in the 39th week of 1976. Don't change them unless they test bad in a good mutual conductance tube tester. The number 188 on the tube is for GE. RCA would be 274 and Sylvania 312. Fender used them all, and they are all better than what is available now


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Post subject: Re: Fender 1976 Vibrolux Silverface (Tube Manufacture??)
Posted: Sun Feb 27, 2011 10:58 am
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willsmusik wrote:
The 12AX7 tube is a USA made General Electric made in the 48th week of 1976 and the 12AT7 is also the same make and made in the 39th week of 1976. Don't change them unless they test bad in a good mutual conductance tube tester. The number 188 on the tube is for GE. RCA would be 274 and Sylvania 312. Fender used them all, and they are all better than what is available now


Correct!

It was quite common during the mid/late silverface era for Fender to purchase OEM tubes from various US manufacturers and have these bottles marked with the Fender logo. GE, RCA, Sylvania, Westinghouse, and Philips were all frequent vendors. These tubes bear no relationship whatsoever to the current crop of Groove Tubes currently hawked by FMIC. They were some of the finest bottles that anybody's money could buy -- most of them built to mil-spec standards and as durable as durable could be.

Arjay

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Post subject: Re: Fender 1976 Vibrolux Silverface (Tube Manufacture??)
Posted: Mon Feb 28, 2011 6:57 am
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It is very likely they are original tubes.I have found that Rca 12ax7 grey plates sound very familiar to what those fender labeled tubes will sound like


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