Raytheon and Sylvania 12ax7 differences

[brads]

Can anyone describe the differences (plates, getters, etc) between blackplate Raytheon and Sylvania 12ax7s?

[teefus]

i have some of both at home and will post a jpeg later tonight if no one responds by then. craig

[Timbre Wolf]

Both Raytheon and Sylvania black-plate 12AX7 have shiny black plates (not dull black like RCA). Older Raytheon have a square-getter, but the "square" is connected to the plate tab with a vertical "stem" wire, going to the center of one of the sides of the square wire. I've only seen square-getter black-plate Sylvanias, never round ones, and the square wire is mounted directly to the plate tab, from one of the corners of the square wire. Here are some more differences:

Raytheon - On top of the upper mica disk, there is a third, partial mica - it has a shape that, to me, is reminiscent of a kind of paper clip (you'll know it when you see it). The plate tabs that come through the mica disks are cut in a single, perpendicular line. These tubes often have the EIA code of 280 somewhere on the tube (usually P280), and may have a two-letter code that begins with "A" (AS is common) etched near the upper side of the glass.

Sylvania - Plate tabs are cut three times each: one perpendicular, and two at ~45deg. angle, so they appear more rounded than Raytheons (depending on your vision).

Square Getter Raytheon:
http://i6.photobucket.com/albums/y223/guohengji/12AX7/IMG_5111.jpg

Round-Getter Raytheon:
http://i14.ebayimg.com/01/i/08/8d/ef/2e_1.JPG

Sylvania 12AX7:
http://www.eecs.berkeley.edu/%7Eloarie/12AX7/img7.gif

How's that?

Tubemonger (http://www.tubemonger.com/)'s tube picture library (https://69.36.182.51/NOS%20Tubes%20Picture%20Library/index.html) has more detailed photos to peruse (apologies for future viewers as the photos disappear - I lifted some from current eBay auctions)

- Thom

[brads]

Thanks much for the detailed reply. Time to dig them out and see what I have.