Unidentified 12AU7

NOS, modern, dating and identifying.

Unidentified 12AU7

Postby deForest46 » Wed Sep 18, 2013 4:31 pm

Hi,

My research trying to ID this tube led me to this Forum.

The tube had masking tape on it with 12au7 and good written on it and also had a very faint capital letter R still visible. I could also see a faint horizontal octagon with 12au7 printed. I removed the tape and with it went he faint R.

My observations:
This tube has 4 seams that appear as very prominent ridges. The D getter is at a 45 degree angle, no supports and has a foil bar. The tube has copper posts, 17mm welded plates, no holes.

The code on this tube is between the pins as shown in the picture. Triangle with either a smudged capital E or stylized lower case t.
The second line reads K6R. Philips codes indicate lower case k6 as an ECC82?

I have come up with 3 possibilities, this is either a Matusishta tube, a Copenhagen tube or an early Heerlen tube.



I welcome discussion on this to try to solve this mystery,

Frank

Image
Image
Image
deForest46
 
Posts: 2
Joined: Wed Sep 18, 2013 2:38 pm

Advertisement

Banner ads are available for $25 a month. PM or Email me at Info@wallaceamps.com for more details.

Re: Unidentified 12AU7

Postby deForest46 » Wed Sep 18, 2013 4:35 pm

more images

Frank

Image
Image
Image
deForest46
 
Posts: 2
Joined: Wed Sep 18, 2013 2:38 pm

Re: Unidentified 12AU7

Postby Jeff West » Thu Sep 19, 2013 10:55 pm

Hey Frank- The Philips codes on the bottom indicate ECC82 manufacture in May 1954 at Philips Copenhagen plant, assuming that's an "E". I've seen others of these spot-welded early Philips ECC82 and ECC83s from late 1953 through mid 1954, with both Copenhagen and Heerlen factory codes (which differ only in orientation of the triangle). Also with factory code that's like a mirror image of Heerlen triangle, said to be Eindhoven by some although it's not in any official Philips list I know of.

The "R" if white may likely have been "RCA", and that would also be consistent with labelling as "12AU7"for U.S. sale. RCA sourced some of these spot welded Philips 12AU7s and 12AX7s and sold them as RCAs domestically, believe it or not, I have a few of those. When the RCA shipping date codes are visible on the tubes they're usually from early 1954, on the ones I've seen. IIRC, by 1955 all the Philips miniatures were crimped not spot welded.

-Jeff
Jeff West
 
Posts: 65
Joined: Fri Jun 13, 2008 12:19 am


Return to Tubes

Who is online

Users browsing this forum: No registered users and 3 guests


cron