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In Reply to: RE: Heerlen Philips Factory 12ax7 Date Codes posted by vmazzone@fastmail.fm on December 27, 2014 at 13:03:22
Straight up triangle is Phillips Copenhagen.
That said, this is the first I've seen the codes on the bottom glass from Phillips/Amperex. I've always seen the codes acid etched in the glass in the area of the bottom mica.
IIRC, Siemens and/or Tele codes them as such.
Cheers,
W
Follow Ups:
The codes on the bottom of glass were used by Philips factories from 1950 -1956. The Philips new codes were acid etched on the side of the tube from around 1956 onwards. Philips old code dates require a lookup table to decipher manufacture dates. The more familiar new codes follow the factory , year, month numbering system.
Looking right at the Phillips factory valve codes manual, there's the FM/TTC and so on, at the bottom of the glass.
Thanks for the correction.
Cheers,
W
I am convinced by the shadow of a doubt, that you are discussing Philips, not Phillips. Please be advised and alter your editor functions. Since these tubes are so dear, I don't even look into buying until recently. I acquired a few tubed headphone amps and their power tubes. I am an inveterate tube roller and heard how much better they sounded with rolled tubes so I broke out my 16 Y.O. stash and made some subs very quickly, with good results but didn't have a lot of the subs for the power tubes . So... I on the hunt again.
As an aside I am surprised what a tube sellers maker up is on a single tube. E.G. a Metal based nos testing in original box, 6SN7W give you $30 but charges over $300 for the same tube while retaining the option to sell it back to you. A true story I kid you not.
I will have to sell privately.
Steve
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