3 X ECC83 12AX7 Valves Tubes 1 Made By Mullard B7 L2 Date Code Blackburn BNIBA lot of questions have been asked about when a tube is made, so here you go, a quick guide on how to decipher the date codes. The code is broken down into 3 or 4 characters. The first 2 characters are the most important ones since factory code would show where a tube was made and year, well, this one is super important since sound changes quite a bit for the same tube from the same place depending on a year. For 3 character codes 8 means , for 4 character codes, 8 means either or that depends on change code — more about that later. Date codes are usually done with acid, so they are burned into glass.
Dating mullard valves
You would know through your dealings with vintage electronics that a reasonable standard for date codes really only began to appear in the early 70's. Prior to this it was pretty well manufacturer dependant and basically obscure!
I got an old Mullard 12AX7 recently(shield logo) and I'm curious to know how old it is. Anyone know how to date them? Thanks. My recent visit to the Mullard Blackburn factory got me interested in identifying the origin of the few Mullard tubes I own. The factory, date of. Generally (and I can't express that enough) a Mullard or Philips vacuum tube The Australian made Mullard tubes generally have a date code.
The following description is applicable to Mullard and Philips vacuum tubes, it may also apply to other manufacturers but only by coincidence. Mullard in Australia also used a straight 3 digit number code that was a 2 digit year code with the month being last - YYM - but this was not a generally used code.
Sorry but I little info on these pre 56 codes:. The obvious problem with the year code is that it repeats every 10 years but you can loosely say that a 3 character date code would have most likely manufactured prior to 56 - This is not true, many companies used it. GE used an etched dot system to mark their tubes.
Most Philips valves are marked with a group of symbols which contain coded or country of origin in the case of bought in valves, and the date of . Mullard Radio valve Co., Mitcham Mullard Fleetwood (after 18 Nov ). TUBES DISPLAY THE MULLARD CODES J83 B4E1 = BLACKBURN, U.K. example: IX1 B5B4 AND IX1 B5C1 IX = 6ES8 ECC, 1 = CONSTRUCTION #. This is why you see even major brands like Sylvania with RCA date codes. Ironically, European tubes like Telefunken and Mullard were seen as inferior to US.
If you see these dots, you know you have a GE tube. Recent Posts.
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Only Sylvania and National Union had the equipment to make them. Despite what a tube has printed, they were made by one of the two companies only. They had a contract with a large company to print their logos on the tubes. It was in the interest of companies like DuMont, Admiral, Emerson etc to have their own logos on the tubes that they supplied in their equipment.
They did this in hopes that when a tube failed the customer would order a tube with the same brand as their equipment at a markup so the company would profit. The manufacturer sold in bulk to a wholesaler or distributor that marketed the tubes differently for a profit. There are many brands out there that never manufactured their own tubes.
To make things worse, these companies usually removed any clues as to who made the tube like EIA codes. This is actually more common today with New Production tubes.
Some common vintage re-branders are IEC, United, Ultron, Arcturus post sInternational Service Master and moreIn the cases where the country of origin is incorrect, it usually had to do middle man companies in Europe trying to get around regulations.
There were many trade sanctions due to the various wars that went on while tubes were still being produced in bulk. Here is a list of European factory codes courtasy of audiotubes. A lot of questions have been asked about when a tube is made, so here you go, a quick guide on how to decipher the date codes.Microphone Tube Test - Amperex/RCA, Mullard/Dumont - 6299 E88CC
The code is broken down into 3 or 4 characters. The first 2 characters are the most important ones since factory code would show where a tube was made and year, well, this one is super important since sound changes quite a bit for the same tube from the same place depending on a year.
For 3 character codes 8 meansfor 4 character codes, 8 means either or that depends on change code — more about that later. Date codes are usually done with acid, so they are burned into glass.
For the most European tubes made after date codes are located on In this case it's B0D (this is for Mullard, Blackburn – – April). Valves used by the British military Armed Services were marked with a CV or common valve name which was defined by the Inter-Service. MostAmperex, Mullard, Philips and Valvo tubes are marked with a group of to the type, place of manufacture or country of origin, and the date of manufacture.