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 Post subject: Sylvania Vacuum Tube Date Codes?
PostPosted: Nov Thu 09, 2017 6:19 am 
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Location: Seaside, Oregon
I have a bunch of Computer grade Sylvania 6350's made for the Buroughs Corp. All have 312 manufacturer codes and a date code of 339 on them. How would you read this. These tubes I'm guessing are from the 60's. Hope you can help. Thanks, John


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 Post subject: Re: Sylvania Vacuum Tube Date Codes?
PostPosted: Nov Thu 09, 2017 3:06 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Monte Vista, CO. USA
If they are 60's, then the date code represents the 39th week of 1963. The 1st number is the year, the next 2 numbers are the week.
-Phil


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 Post subject: Re: Sylvania Vacuum Tube Date Codes?
PostPosted: Nov Thu 09, 2017 3:09 pm 
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Joined: Jul Tue 20, 2010 8:07 pm
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Location: Twin Cities, MN
I have a bunch of Sylvania 5751 with codes JAK, JAW, JAO, BAW, which I am assuming is the date code.

I've searched the Web for a key to Sylvania date codes, but no luck. Most other manufactures can be found, but couldn't find Sylvania.

Anyone have a source?

As for the OP code of 339, could be the 39th week of 1963?


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 Post subject: Re: Sylvania Vacuum Tube Date Codes?
PostPosted: Nov Fri 10, 2017 11:12 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Orlando, FL, USA
The 6350 was registered in December 1953. If the tubes have square or "D" getters, they would be early production 39th week of 1953, but if they have halo getters, 39th week of 1963.

The 3 letter Sylvania markings are not date codes. They are production lot codes. I am sure when Sylvania was in business they could have used internal paperwork to trace a production lot to a specific line and date, but there is no translation scheme to get years and dates out of them. It is far more likley that the two letter codes on the same tubes mean something, but no one knows for sure.

Jim Cross


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 Post subject: Re: Sylvania Vacuum Tube Date Codes?
PostPosted: Sep Sun 19, 2021 9:00 am 
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Joined: Sep Sun 19, 2021 8:49 am
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Hello all, my first posting.

New into audio tube amps and rolling, I am reading a review of a hybrid amp I have and the Sylvania 6AK5 are recommended as a good tube set for the characteristics I am after. Pre 1963 are said to be the ones needed as after this they apparently don't have the same characteristics. Based on this discussion and the fact when I asked one seller for the dates he said he did not know sorry, how would the reviewer know, again I am new to this so apologies if I am missing something obvious.


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 Post subject: Re: Sylvania Vacuum Tube Date Codes?
PostPosted: Sep Mon 20, 2021 1:34 am 
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Joined: Sep Mon 16, 2013 2:42 am
Posts: 5101
Location: Tucson, Arizona U.S.A.
Shadez wrote:
Hello all, my first posting.

New into audio tube amps and rolling, I am reading a review of a hybrid amp I have and the Sylvania 6AK5 are recommended as a good tube set for the characteristics I am after. Pre 1963 are said to be the ones needed as after this they apparently don't have the same characteristics. Based on this discussion and the fact when I asked one seller for the dates he said he did not know sorry, how would the reviewer know, again I am new to this so apologies if I am missing something obvious.

Another thing to consider is that if a manufacturer ran short of a particular type or didn't want to set up a production line, they would buy the tubes from some other manufacturer and have them labeled for the brand that was buying them. So the brand name on the tube is not a guarantee of who made it.

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Jim Mueller

Who's that swimming in the punch bowl?
It's Walter Wart, the freaky frog!


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 Post subject: Re: Sylvania Vacuum Tube Date Codes?
PostPosted: Sep Mon 20, 2021 1:01 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Fernandina Beach, FL
Jim Mueller wrote:
Shadez wrote:
Hello all, my first posting.

New into audio tube amps and rolling, I am reading a review of a hybrid amp I have and the Sylvania 6AK5 are recommended as a good tube set for the characteristics I am after. Pre 1963 are said to be the ones needed as after this they apparently don't have the same characteristics. Based on this discussion and the fact when I asked one seller for the dates he said he did not know sorry, how would the reviewer know, again I am new to this so apologies if I am missing something obvious.

Another thing to consider is that if a manufacturer ran short of a particular type or didn't want to set up a production line, they would buy the tubes from some other manufacturer and have them labeled for the brand that was buying them. So the brand name on the tube is not a guarantee of who made it.

What Jim has said is so true. For instance, I can often "assume" who made a tube by the ink and font used on the tube. Example, I have several 7591 tubes labeled "RCA". I do not think that RCA actually made that tube number. But a close look at the marking on the tube screams "Sylvania" by the color, location and font of the marking.

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Don


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 Post subject: Re: Sylvania Vacuum Tube Date Codes?
PostPosted: Sep Mon 20, 2021 1:17 pm 
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Joined: Jan Mon 18, 2010 2:13 am
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Location: Dayton Ohio
The 6AK5 is a miniature VHF pentode designed to be an RF amplifier in the range of about 30-400 MHz.
They should all be designed to have the correct characteristics set forth of what a 6AK5 should be regardless of manufacture date.

-Steve

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