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Old 11-11-2007, 10:23 PM
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Findm-Keepm Findm-Keepm is offline
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Join Date: Jun 2007
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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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CET- Consumer Repair and Avionics ('88)
"Capacitor Cosmetologist since '79"

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