Understanding and Reading tube Numbers

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Understanding and Reading tube Numbers

Post by Guest on Sun Mar 23, 2014 5:44 pm

As suggested about a week ago, it is time to start a discussion of all the numbers on vacuum tubes and what they mean.

I'll give an example of a tube to start and our experts can guide us on better understanding what all these numbers mean.


Admiral 12AU6 188-20 61-17

Even though most of us understand the 12AU6 portion it wouldn't hurt to document it here.

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Re: Understanding and Reading tube Numbers

Post by Alan Douglas on Sun Mar 23, 2014 7:31 pm

188 is the EIA identification number for GE. The usual following number is 5 which identifies one of their plants; I don't know where 20 was. 61-17 is the 17th week of 1961.

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Re: Understanding and Reading tube Numbers

Post by 35Z5 on Sun Mar 23, 2014 8:01 pm

Here's a list that has many of the mfgr's... I posted it because the Tung-Sol pictured has their mfgr code all in one line but not separated

reads 3226135, 322 is Tung-Sol 1961 & week 35...

http://www.blackswampaudio.com/Tubes/USA_Manu_Codes.php

Most mfgr used a two line format that would read:

322
61-35

Though not always, dates like this often mean OEM tube, across the counter tube sales generally have a two or three digit alpha code that requires a chart... AA on a RCA tube is Feb'64, with the code progressing AB, AC, etc for each month...

BTW No RCA code for Jan'64 isn't ZZ, it's NM, can count backwards to KC to work your way back to Sept'56...
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Re: Understanding and Reading tube Numbers

Post by 35Z5 on Sun Mar 23, 2014 8:52 pm

Notice that chart doesn't include Zenith...Why??? Excepting for picture tubes, they didn't manufacture tubes... The OEM Zenith tube I pictured in the other thread could just as easily been built by RCA or GE and still say replace only with a genuine Zenith tube...

Here's a Emerson tube built by Sylvainia that makes same claim as the Zenith(Emerson uses the word renew vs replace)... Unlike the vertical format on the Zenith tube, this one also uses the one line format... I'm guessing it varied by system used by the buyer...



Date on this one is 1966 week 39... Often the first digit of year is omitted, if the device isn't avail have to make a educated guess... In this case tube has a button stem and no press, likely ID's it as built later 50s or newer...

As a refresher here's that Zenith tube again...

Date is 1966 week 13...

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Re: Understanding and Reading tube Numbers

Post by Ron Pond on Mon Mar 24, 2014 6:12 am

Here's a list of Philips and Mullard date and location codes;

http://frank.pocnet.net/other/Philips/PhilipsCodeListAB-v8.pdf
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Re: Understanding and Reading tube Numbers

Post by 35Z5 on Tue Mar 25, 2014 12:27 pm

Here's a Genuine Zenith mfg'd by GE, has their 188 code and a 1979 date... This is a new replacement tube...



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Re: Understanding and Reading tube Numbers

Post by 35Z5 on Wed Mar 26, 2014 6:05 am

Here's what you got when one bought those 33 cent specials pedaled by sellers in the electronics rags... Every one of these are branded Nation-Wide and marked used or second(only on the Major Brand box though)...





There is a code date of 6-68 on this 50EH5 but no mfgr code... This tube is undoubtedly used and mfgred by RCA, is from 50s, maybe early '60s...

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Re: Understanding and Reading tube Numbers

Post by 35Z5 on Fri Jun 06, 2014 1:26 pm

Would the real FoMoCo please stand up???

Here are 6V6 & 6X5 from a '54 Ford radio, 6X5 on right supplied by RCA, the 6V6 is a GE, while small signal tubes were supplied by Sylvania...

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Re: Understanding and Reading tube Numbers

Post by Guest on Tue Aug 26, 2014 9:37 pm

I love this information on tubes and have another question.

I've heard it said that Radio Shack and Lafayette radio vacuum tubes are not of good quality. So........I found I have 2 NIB Lafayette 35Z5 tubes with nothing but Lafayette stamped on the envelope. How do find out where these tubes were made? Maybe this explains why they are considered by some to be junk.

Notice the tube number Tom? Neutral

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Re: Understanding and Reading tube Numbers

Post by 35Z5 on Tue Aug 26, 2014 11:47 pm

Uhhh whadt number??? All I can see is a mirror image... Wink

More often than not tubes branded for companies such a Laff a lot & Rat Shack were from Japan and about only method that would determine who orig mfgr'd it would be compare with same number from known supplier...

Even that doesn't always help as construction details often vary every few years...

Got a picture???
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Re: Understanding and Reading tube Numbers

Post by Guest on Wed Aug 27, 2014 12:05 am

They are in the shop maybe I can take a photo tomorrow and post it.

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Re: Understanding and Reading tube Numbers

Post by Wildcat445 on Sun Nov 09, 2014 3:32 pm

I have a sleeve of Lafayette 35Z5's and I haven't had any problems with them. What about Ken-Rad? Why don't I see a code for them.

WC

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Re: Understanding and Reading tube Numbers

Post by Resistance is Futile on Sun Nov 09, 2014 5:04 pm

Radio Shack Did have a line of tubes that were Realistic Gold series (-gold plated pins,) and they declared that they were guaranteed  for Life.
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Re: Understanding and Reading tube Numbers

Post by 75X11 on Thu Nov 13, 2014 7:10 pm

Radio Shack's current tube availability beggars the question, who died? Very Happy
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