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Old 11-11-2007, 12:51 PM
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deciphering GE tube date codes.........

Does anyone know or have a list of how GE dated their tubes. GE did away with the year-month coding and went to a two figure alphabetical system such as:

"RY" or "KJ" etc.

And under that would be the EIA number, which was 188 (which was GE)

Ive found a few websites that mention this, but do not have any information on deciphering the letters. Supposedly the reason for this change was to prevent the customer from identifiying an "old tube" in a "new TV" for example. Curious if there is a published list somewhere?
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Old 11-11-2007, 02:43 PM
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Sylvania also seemed to use the two-letter date code system for a while too.
I have often wondered about the letter code too ...this may have been kept a factory "secret" and maybe even the distributors did not have the code info.
However I have seen some GE tubes (usually original equipment tubes in GE TV's) which do have the standard year month code (like 74-19, etc.)
Also it seems like tubes that were made for other makers by GE often have a real date code, too.
We have a Leslie speaker which have some "RCA" 6550's which are made by GE with an 82 date code...also a "Fender" 12AX7 made by GE with a 78-26 date code.
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Old 11-11-2007, 10:23 PM
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Doug and others,

Having worked at a GE parts dealer (Cain Electronics Co, Inc) in the early 80's, I can speak of this first hand. GE used two codes - one for OEM stuff and one for replacement tubes. The two code scheme was GE's Owensboro, Kentucky plant's means of preventing the two types of tubes from ever being swapped, i.e. having an OEM tube returned for warranty at a parts dealer or a replacement tube being returned through the GE Warranty repair system. RCA had a similar scheme, but theirs just added letters to their existing OEM codes.

While I worked at Cain, we had a list of the two letter codes, and we were at the middle of the alphabet for the two years I worked there. G, H and K were the common second letter - they were the manufacture years 81, 82 and 83. The first letters were a simple A-M (I was skipped, I believe) that stood for the month of manufacture. Tubes were manufactured in massive lots, so for about 10 months or so, all the 6GH8's we sold (100's - we ordered them in 2400 tube lots, I recall) had the same date codes. Again, it rarely mattered - if the codes were there on the tube and were recent, we took the tube in on warranty, with a receipt. We only swapped the bad tube with a good tube and sent the customer on their way. We had one or two shops that tried to use our shelf stock as troubleshooting aids, hence the no return, just replacement policy.

Yes, the codes repeated over the years of GE's presence in the tube market. I honestly think they did this to keep it simple - who is going to return, in 1990, a 6AF3 sold in 1980 with a 1976 date code? Very few folks, I imagine.

OEM codes are all the familiar EIA/RETMA year/week scheme. RCA had an early white paper detailing how the EIA numbered the weeks. I was always leery of anything with a "51" week code - too close to the Christmas holiday, and perhaps the quality slipped, I dunno.

I could ask one of my fellow co-workers that still works at Cain if he can produce a code list - not likely after all the company has been through. It was sold to Norfolk Wire, dropped most replacement parts lines, and now sells mainly tools, accessories and supplies to the industrial/government customers. But Bernie may have them nonetheless.

GE replacement HV triplers had a similar two letter code - we never could decipher how it went, and it may have been a batch or QA inspection code.

Hope this helps.

Cheers,
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Old 11-11-2007, 10:38 PM
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Originally Posted by Findm-Keepm View Post
Doug and others,

G, H and K were the common second letter - they were the manufacture years 81, 82 and 83. The first letters were a simple A-M (I was skipped, I believe) that stood for the month of manufacture.
I called my brother on this - he worked at Cain too, for longer than I did. He corrected me on two things -

(1) we were at "L" for the year code when we both quit in early January 1984, and J wasn't skipped, so if L was 1983, you could go up or down the alphabet and figure the year from there.

(2) Also, the months were labeled different for different years, even vs odd perhaps. A-M and N-Z or thereabouts were the two month groups, always ascending. So, AL or NL was a January, 1983 tube, depending on the month code group for 1983.

He also suggested I speak with Bernie - maybe I'll have more.

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Old 11-12-2007, 12:24 AM
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So, GE was still making tubes in Kentucky in 1984?? Wow! My aunt worked for Ken-Rad (Kentucky Radio) in the 1930's and '40's in Owenboro. Womder if it was the same plant...Things that make you go hmmmm.
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Old 11-12-2007, 12:43 AM
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Slightly OT; but, I wonder when companies like RCA, GE, and Sylvania stopped making vacuum tubes in this country? I do remember buying some Philips ECG tubes from the local parts house in the mid '90's for some of the tube sets I brought home. Of course, these may have been 10 years old or older when I bought them.
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Old 11-12-2007, 08:33 AM
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Originally Posted by radiotvnut View Post
Slightly OT; but, I wonder when companies like RCA, GE, and Sylvania stopped making vacuum tubes in this country? I do remember buying some Philips ECG tubes from the local parts house in the mid '90's for some of the tube sets I brought home. Of course, these may have been 10 years old or older when I bought them.
And some of those Philips ECG tubes were made in Europe. I've got several dozen NOS Philips ECG tubes that were made in Germany, Netherlands and even Japan. Dwindling use of tubes did in the US plants - most consumer equipment was solid state by the mid 70's and tubes made into the 1980's were mostly for replacement and/or military purposes. RCA made RF tubes well into the 90's here in the states - the Government made several "lifetime buys" of the most used tubes. Then, once modernization/retirement of old systems came about, they dumped the tubes through DRMS, and you can now find most of them on Fleabay.

Here in Norfolk, the DRMO auctions I went to in the early 90's, when they were still "live," were full of "War Stock" tubes. Funny thing was, few lots were bought, and those lots probably because they had "key" tubes in them. I picked up one pallet lot of new tubes, sockets, and other parts that were removed from the USS Wisconsin when she was reactivated. My price? A $2.50 token bid, placed after they couldn't get the $5 opening bid. (Hey, it was January, 15 degrees outside, and the auction was in an unheated warehouse!)

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Old 11-12-2007, 08:39 AM
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Originally Posted by wkand View Post
So, GE was still making tubes in Kentucky in 1984?? Wow! My aunt worked for Ken-Rad (Kentucky Radio) in the 1930's and '40's in Owenboro. Womder if it was the same plant...Things that make you go hmmmm.
A-yep. Owensboro also was home to their replacement semiconductor line, but was merely a marking and packaging operation. Any one remember their "PRO-LINE" promotions with the little colored GE stickers?

Cheers,
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Old 11-12-2007, 08:20 PM
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One of the Leslie speakers we just worked on was built in 1992 and had 1992 date code MPD 6550 tubes in it. These were made in Owensboro in the GE factory and I think these were the last "regular" glass tubes made here by the MPD co. which took over the GE tube factory, and the last year of glass receiving tube manufacture there.
They still used the "Electronic Tube" script logo but had no GE logo. They said "Built to GE specs by MPD Inc. in Owensboro, Ky." They had a regular 92-xx date code on them.
I don't think they had a sandblasted stencil tube number on them though...maybe that machine had gone into mothballs due to the small amount of glass tubes still being made?

Thanks for posting the GE tube code...in years of searching on the internet I have seen no explanation of it till now!
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Last edited by Chad Hauris; 11-12-2007 at 08:31 PM.
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Old 11-13-2007, 11:15 AM
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Very interesting stuff!

I have a couple early 70s GE TV sets and at least some of the tubes have 2 date codes. One appears to be when the tube was made and the other is a couple years later, apparently about the time the set was built.

If I have my story straight, GE bought Ken-Rad in order to get into the tube making business. I think that was in the late 30s but I can't remember for sure. Both GE & Ken-Rad lines were retained for a time. One of the oddities I have at home is a GE circalite (one of those round loop flourescent bulbs) repackaged as a Ken-Rad.
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Old 01-05-2012, 06:24 PM
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More on Dating GE Tubes

I hope the people who posted the previous information about dating GE tubes are still watching. I have found this information greatly helpful and want to pose some more questions.

I presume that the code 188-5 indicated the Owensboro plant, but I also have some tubes coded 188-21. Do you know what plant that is? In this case, the tubes are GE 8425A/6AU6As. 8 of them are in the same Tektronix plug in, all marked and coded the same, so they are certainly OEM. The code 69-13 appears on them, but then, just above the 188-21 code appear the letters JZ. Could that be a Rosetta Stone? I also have a 6DJ8 with HZ over 188-5, and another one marked HW - both of these are likely OEM tubes. I also have a 6DJ8 which was used as a replacement in a scope and which is coded JL over 188-5. Does this imply that there were two different GE codes, one for OEM tubes and one for open market supply?

The codes ending in Z seem to be inconsistent with the code sequence discussed in earlier posts related to Owensboro tubes. I wondered if anyone can shed any light on this.

When I worked at ARC back in the 50s, we got most of our tubes from GE, and all the ones I still have are open date coded. I have a group of JG 6AU6WA coded 4-48 over 188-5 and 6136 Five Star dated 60-04 over 188-5. I presume that the 4-48 indicates the 48th week of 1954.

These codes are extremely important to dating equipment as you well know, and are fascinating besides. Any comments or further insight would be greatly appreciated.

Paul Hart
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  #12  
Old 01-23-2012, 08:52 AM
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GE Tube codes

Hi I was looking for information for a GE branded SAR4 tube I have. It is stamped as manufactured in Great Britain and has a date code of HZ 188-5. I'm guessing the same date codes were used at various manufacturing plants since this tube was not manufactured in the KY plant, but in the UK. If you ever find more information, please let me know. Thanks.
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Old 01-23-2012, 12:10 PM
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I would think this may be a Mullard 5AR4 tube labeled as a GE.
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Old 01-23-2012, 12:25 PM
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Originally Posted by Chad Hauris View Post
I would think this may be a Mullard 5AR4 tube labeled as a GE.
Thanks, do you have any idea of the date code?
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Old 01-23-2012, 01:09 PM
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If anyone here is a member of the Tube Collectors Association, there was a major article on deciphering GE date codes in the December 2010 issue of the newsletter.

http://www.tubecollectors.org/tcoll2010.htm
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