Dating vacuum tube
Dating vacuum tube - Philippines cam site
By David Mell 2016 Copyright All Rights Reserved The topic of who really produced a tube and where causes a huge amount of confusion in the community.
Note: The following applies to Mullard & Philips tubes made after 1956, prior to this the manufacturers used a change code. Prior to this it was pretty well manufacturer dependant and basically obscure! 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.Vacuum tubes, or thermionic valves, are arrangements of electrodes in a vacuum within an insulating, temperature-resistant envelope.Although the envelope was classically glass, power tubes often use ceramic and metal.1) Factory code , 2) Year of Manufacturing, 3) Month, 4) Week (this is usually on tubes manufactured after 1960) 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 1958, for 4 character codes, 8 means either 1968 or 1978 (that depends on change code – more about that later).Finding the code could be very easy, but occasionally it’s quite challenging.Start with naked eye and if you can’t find it use magnifying glass.Sometimes even the best tube dealers get stumped and you’ll see all kinds of incorrect listings on the web.Often, the printed brand or printed country is incorrect.The simplest vacuum tubes resemble incandescent light bulbs in that they have a filament sealed in a glass envelope which has been evacuated of all air.