Siemens codes

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In Reply to: Identifying NOS Siemens Tubes posted by erlandsen on September 21, 2004 at 03:33:22:

These codes are a mystery to me, too. Perhaps your post will lead to a response from someone out there who knows this subject. But in the category of here's what I know:
Late 50's and early 60's Siemens tubes have etched codes toward the bottom of the tube, in 3 rows, running parallel to the pins. In the top row I have seen a letter followed by an "O" with a "/" through it. (I don't know what this letter or symbol means.) In the second row there is a number and a factory code. (An "=" symbol with a "|" through it denotes the Siemens, Munich factory.) And in the 3rd row there is a number and a letter. These early tubes have a halo getter inside the top of the tube and the halo is supported by a bar rising from the splatter shield.
As I understand it, at some point, by the mid-60's at least, the etched coding stops and codes began to appear on a metal tab running from the upper mica. Perhaps someone can tell us how to read thes codes. The getter structure is the same as stayed the earlier tubes, with a halo-shaped getter supported by a bar.
In the early '70's the getter structure changed to the "A-frame," with a halo supported by 2 bars in the shape of an "A". These tubes also have a tab inside with codes.
Then in the late '70's and continuing into the '80's, the getter structure changed to what I think you describe, with a shinier halo loop supported by a single wire (and no splatter shield). These latter tubes also have the metal tab with codes. They are also usually the least favored sonically (but YMMV). And in my experience I prefer the earlier one-bar tubes to the A-frame type.
That is my .02, all based on my own observations and what I've been able to pick up here and there. The factory codes are taken from the list which also includes the familiar Philips/Amperex codes.
Others with more or better information, please help.

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Follow Ups Full Thread

Topic - Identifying NOS Siemens Tubes - erlandsen 03:33:22 09/21/04 (8)

Siemens codes - JFB 05:42:10 09/22/04 (0)

More info ) not much help though )) Re: Identifying NOS Siemens Tubes - ruffscruff 11:58:03 09/21/04 (0)

Re: Identifying NOS Siemens Tubes - Meister 05:27:54 09/21/04 (5)

Re: Identifying NOS Siemens Tubes - erlandsen 05:57:48 09/21/04 (4)

Re: Identifying NOS Siemens Tubes - 254mm 07:52:12 09/21/04 (3)

BTW 254mm - The picture you posted above is ours (nt) - tubemonger 08:39:33 09/21/04 (2)

Re: BTW 254mm - The picture you posted above is ours (nt) - 254mm 09:36:45 09/21/04 (1)

Cool - no prob at all. - tubemonger 09:47:36 09/21/04 (0)

Follow Ups

Siemens codes - JFB 05:42:10 09/22/04 (0)

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