PDA

View Full Version : Can anyone help me identify this RCA 12AX7?


Curt
11-08-2008, 07:10 PM
Can anyone help me identify this tube.
It's new in a the original RCA box. It's made in Britain.
The "HA" has me confused.

http://img.photobucket.com/albums/v604/PrivateStock/RCA.jpg

http://img.photobucket.com/albums/v604/PrivateStock/RCA1.jpg

rockon1
11-08-2008, 07:24 PM
I have a few fake Mullards like those. See the semi circle holes on the sides of the plates? Can you see right thru them? If so its probably made in India by Bharat Electronics, Ltd. (BEL), . -Never actually owned by Philips but used Philips tooling .

If you cant see thru them look for etch codes near the base of the tube. The code should stasrt with B### . Heres a link explaining Philips family etch codes.

http://www.tube-classics.de/TC/Tubes/Valvo/Phlipscode.htm


.....

Jeff West
11-08-2008, 08:00 PM
Really only a fake Mullard to us, it's a "real" RCA but sold by them after they stopped making tubes themselves. The "GT. Britain" is definitely a lie!

"HA" is an RCA applied shipping date code, for 4/79. The dot you see after the letters is their designation that the tube was actually purchased from another manufacturer and then sold new by them. You'll see those following dots inconsistently from the '50s to the '70s, on (some) RCA branded tubes they bought from Mullard, Matsushita, GE, etc.

That one's actually a Matsushita (although RCA also did BELs in the '70s so that's another good likely suspect!). Some of the '70s ones can be real hard to tell from BELs sometimes, esp in photos, but one thing that can help ID is as follows (something I wrote before in another place):

"It's true that some '70s era Matsushitas closely resemble Bharat-made versions from the same time frame, with similar getter rings, top seams, grid rods, etc., and both can have the well-known "round holes through to inside of the plate" ruling out other contenders but not nec discriminating between Japan vs. India. Also, both of these widely carried other brandings, including some of the same ones.

There are some characteristic "feel" details that can help, like the slight cants of the halo, etc., also a few other things if you can really see everything "in hand". But here's a more concrete tip that might help, if you've got "holes thru" but you can't see all the other details.

As you face the plates head on, i.e., POV perpendicular to the broad area of the plate, and check the mica edge, with a known Matsushita you will likely find that you've got one of the standard mica points centered exactly in the middle of the plate and pointing right at you. With a BEL, you won't, the points are not centered in the midline of the plate, in fact there's a little extra concavity there, with points on either side (also found similarly on some other shortplates like Heerlens). Can often see this in photos."

Two seams on the top of that one, not four, right?

Matsushita ended all tube production in 1979, this one was likely actually manufactured up to a few years before RCA got it and labelled it and sent it out for sale. Nice tube IMO, BTW.

Jeff W.

Curt
11-08-2008, 08:10 PM
Thank you both for the quick answer.
I was rather doubtful it was actually made in GB.

rockon1
11-08-2008, 08:39 PM
As you face the plates head on, i.e., POV perpendicular to the broad area of the plate, and check the mica edge, with a known Matsushita you will likely find that you've got one of the standard mica points centered exactly in the middle of the plate and pointing right at you. With a BEL, you won't, the points are not centered in the midline of the plate, in fact there's a little extra concavity there, with points on either side (also found similarly on some other shortplates like Heerlens). Can often see this in photos."


As usual amazing amounts of information! I have to ask where you have amassed such a vast knowledge of tubes? Its staggering.

You lost me in the part I quoted. "POV purpendicular to the broad area of the plate"? In other words do you mean looking thru the center of the tube-edge of the plates? Also Im gathering not all Matsushitas had the angled getter? thanks Bob :bow

http://i38.tinypic.com/t89m4p.jpg

59Vampire
11-08-2008, 08:54 PM
thanks for the link above

jcs
11-08-2008, 09:56 PM
i think i have at least one of the exact same tube with 'IEC mullard' printed in addition to 'gr britain'.... (thank you jeff!) ...btw,great sounding tube!

rockon1
11-08-2008, 10:11 PM
i think i have at least one of the exact same tube with 'IEC mullard' printed in addition to 'gr britain'.... (thank you jeff!) ...btw,great sounding tube!

These tubes are easily mis-identified. I learn something new all the time(usually from Jeff West!) From memory all the IEC Mullards I own are actual Mullards(Made at the Blackburn England plant ) Bob

jcs
11-08-2008, 10:34 PM
actually the other IEC 12ax7 i have are blackburn mullards as well...

rockon1
11-08-2008, 10:36 PM
actually the other IEC 12ax7 i have are blackburn mullards as well...

Yeah you have to keep your eyes wide open,glasses on(in my case) and magnifying glass in hand! lol! Bob

Jeff West
11-09-2008, 08:47 AM
Hey Bob and Jim and all- Sorry, as usual I'm overcomplicating and can use a good editor. I just meant that if you look at the edge of the mica from the front, facing the ribbed plate head on, it seems that most if not all Matsushita 12AX7s throughout the '60s and '70s will have a "tooth" dead center, i.e., pointing right at you from the midline. In the last photo here, look for example at the point more or less under the first "A" in the orange "12AX7A". This distinguishes them from all the BELs I've checked. I think that'll hold up, but as always, if you find exceptions please post!

Matsushita started doing non-canted halo shortplates, i.e., with added support rod, at least by 1969 and thru at least 1977, going by their own date coded Matsushita-branded specimens. Prior to 1969, the shortplates had canted halos w/o support rod, like Hamburg Valvos. Whether they made more canted ones in the '70s is not entirely clear (to me), a lot of them were first sold new under other brands in the '70s with canted, and unlike the '60s canted these tended to have "holes-through", like the '70s non-canted, but they also could have been manufactured earlier. Well, there I go again . . .

My understanding is that IEC basically had ownership for distribution of Mullard-labelled tubes in North America, and they started putting "IEC" in various forms in the Mullard labelling beginning by ca. beginning of 1965. The "1022" identifier and printing/shipping date code was theirs (and was in use in U.S. for years before "IEC" was added). But "IEC Mullard" went onto a lot of tubes that weren't made in Mullard factories, including not only Matsushita-made 12AX7s (including "10M") but also KT66s and '88s, T-S 5881s, etc. They were official N. American Mullards, but made by non-Philips manufacurers.

And also by other Philips factories outside of Britain . . . I think I've posted before that I've got a couple of authentic "Mullard IEC" labelled 12AX7s with mid '65 "1022" code that are actually 1/61 I61 Munich Siemens, per the etch codes (and Batman ears).

I'll try to return soon to say more about good sources of info for various things related to this thread.

JW

rockon1
11-09-2008, 09:09 AM
Hey Bob and Jim and all- Sorry, as usual I'm overcomplicating and can use a good editor. I just meant that if you look at the edge of the mica from the front, facing the ribbed plate head on, it seems that most if not all Matsushita 12AX7s throughout the '60s and '70s will have a "tooth" dead center, i.e., pointing right at you from the midline. In the last photo here, look for example at the point more or less under the first "A" in the orange "12AX7A". This distinguishes them from all the BELs I've checked. I think that'll hold up, but as always, if you find exceptions please post!

Got it! Interesting distinction.


Matsushita started doing non-canted halo shortplates, i.e., with added support rod, at least by 1969 and thru at least 1977, going by their own date coded Matsushita-branded specimens. Prior to 1969, the shortplates had canted halos w/o support rod, like Hamburg Valvos. Whether they made more canted ones in the '70s is not entirely clear (to me), a lot of them were first sold new under other brands in the '70s with canted, and unlike the '60s canted these tended to have "holes-through", like the '70s non-canted, but they also could have been manufactured earlier. Well, there I go again . . .



Im not looking thru all my non coded suspected BEL tubes...Im not....well not today anyways! lol! I do need to catalog my collection better though.



My understanding is that IEC basically had ownership for distribution of Mullard-labelled tubes in North America, and they started putting "IEC" in various forms in the Mullard labelling beginning by ca. beginning of 1965. The "1022" identifier and printing/shipping date code was theirs (and was in use in U.S. for years before "IEC" was added). But "IEC Mullard" went onto a lot of tubes that weren't made in Mullard factories, including not only Matsushita-made 12AX7s (including "10M") but also KT66s and '88s, T-S 5881s, etc. They were official N. American Mullards, but made by non-Philips manufacurers.


I have a few IEC branded I believe have B codes. Its been a while but I put them in with my B coded Mullards.


And also by other Philips factories outside of Britain . . . I think I've posted before that I've got a couple of authentic "Mullard IEC" labelled 12AX7s with mid '65 "1022" code that are actually 1/61 I61 Munich Siemens, per the etch codes (and Batman ears).

I'll try to return soon to say more about good sources of info for various things related to this thread.

JW

That would be great! Thanks again,:BEER Bob

Jeff West
11-14-2008, 11:52 AM
Agreed, a great number of tubes with "1022" codes are from Blackburn.

A fine multilayered reference site with lots of branches, for Japanese (and some other) tubes online is at:

http://radiomann.hp.infoseek.co.jp/HomePageVT/Audio_EU_Pentode.html (http://radiomann.hp.infoseek.co.jp/HomePageVT/Audio_EU_Pentode.html)

Includes various Japanes manufacturers' dating codes. This site has been references on tubes boards a lot (I think Dai Hirokawa was the first), but great to check out if anyone hasn't. If like me you don't read Japanese, you'll have to deal with some dubious translations.

Another useful reference, for RCA lovers (and would-be daters), if anyone hasn't seen, is online at:


http://mysite.verizon.net/tubetronic/PDF_FILES/RCA%20DATE%20CODES.pdf (http://mysite.verizon.net/tubetronic/PDF_FILES/RCA%20DATE%20CODES.pdf)

Actually, this is scanned verbatim from Tube Collector V.1, no.2, April 1999. That's the publication of the Tube Collectors Association. Some of y'all might want to join. They bring forth especially good direct info on RCAs, due to having a massive archive (160+ shelf feet, two tons+) of classified factory publications, technical papers, and literature, miraculously saved from certain loss to the landfill at the time of the closing of the RCA Harrison, NJ plant in April, 1976 (which effectively ended RCAs manufacture of receiving tubes like we want, also had cascaded negative effect on other US manufacturers). The story of the Dowd-RCA Archive is quite a saga in itself, collector members of the Antique Wireless Association in '75-'76 recognized the future importance of this literature when no one else did, managed to get stuff on pallets and trucked to upstate NY where they were stored in a barn for over 20 years. They're still going through them . . .

As long as we're discussing clues in the mica spacers of vintage 12AX7s, another one that could be useful to someone sometime I've noticed but never seen mentioned anywhere at all is on almost all shortplate Blackburn-made Mullards: specifically, on the edge of the top mica (only; not the bottom one). If you check from the side of the plates (edge on), the top mica on a Blackburn Mullard is readily noticed to have a space where there are no teeth, on each side. This distinguishes them from virtually all other similar looking non-US 12AX7s, Heerlen, Electrohome Canadian, etc. So, in many photos you can immediately get a clear idea that it is or isn't Blackburn, even with no access to etch codes, etc. Now, in my observation this seems to hold up across almost all shortplate Blackburns, I61, I62, I63, 1959 to late '70s, except for the very first few months production of shortplates, I61s from first 6 months or so of production in '59; these have points all around the top mica, just like longplates, Dutch Bugle Boys, etc. Last 1959 I61s and from then on don't . . .

rockon1
11-14-2008, 02:43 PM
Agreed, a great number of tubes with "1022" codes are from Blackburn.

A fine multilayered reference site with lots of branches, for Japanese (and some other) tubes online is at:

http://radiomann.hp.infoseek.co.jp/HomePageVT/Audio_EU_Pentode.html (http://radiomann.hp.infoseek.co.jp/HomePageVT/Audio_EU_Pentode.html)

Includes various Japanes manufacturers' dating codes. This site has been references on tubes boards a lot (I think Dai Hirokawa was the first), but great to check out if anyone hasn't. If like me you don't read Japanese, you'll have to deal with some dubious translations.

Another useful reference, for RCA lovers (and would-be daters), if anyone hasn't seen, is online at:


http://mysite.verizon.net/tubetronic/PDF_FILES/RCA%20DATE%20CODES.pdf (http://mysite.verizon.net/tubetronic/PDF_FILES/RCA%20DATE%20CODES.pdf)

Actually, this is scanned verbatim from Tube Collector V.1, no.2, April 1999. That's the publication of the Tube Collectors Association. Some of y'all might want to join. They bring forth especially good direct info on RCAs, due to having a massive archive (160+ shelf feet, two tons+) of classified factory publications, technical papers, and literature, miraculously saved from certain loss to the landfill at the time of the closing of the RCA Harrison, NJ plant in April, 1976 (which effectively ended RCAs manufacture of receiving tubes like we want, also had cascaded negative effect on other US manufacturers). The story of the Dowd-RCA Archive is quite a saga in itself, collector members of the Antique Wireless Association in '75-'76 recognized the future importance of this literature when no one else did, managed to get stuff on pallets and trucked to upstate NY where they were stored in a barn for over 20 years. They're still going through them . . .

As long as we're discussing clues in the mica spacers of vintage 12AX7s, another one that could be useful to someone sometime I've noticed but never seen mentioned anywhere at all is on almost all shortplate Blackburn-made Mullards: specifically, on the edge of the top mica (only; not the bottom one). If you check from the side of the plates (edge on), the top mica on a Blackburn Mullard is readily noticed to have a space where there are no teeth, on each side. This distinguishes them from virtually all other similar looking non-US 12AX7s, Heerlen, Electrohome Canadian, etc. So, in many photos you can immediately get a clear idea that it is or isn't Blackburn, even with no access to etch codes, etc. Now, in my observation this seems to hold up across almost all shortplate Blackburns, I61, I62, I63, 1959 to late '70s, except for the very first few months production of shortplates, I61s from first 6 months or so of production in '59; these have points all around the top mica, just like longplates, Dutch Bugle Boys, etc. Last 1959 I61s and from then on don't . . .

Thanks for the links/info! I'll have to take some time to peruse them!

Yes Ive noticed the missing teeth (two per mica)on my mullard collection that I just went thru recently. I didnt realise it was Blackburn only. Just did a spot check on a few Seimens and Heerlen short plates and ,yes, they dont have this distinction! Also the 59 Blackburns I have DO have all the teeth as you mentioned. I only own 2 59's I guess they are early-I didnt taken notice of the full code.
I also noticed the few Heerlen's I checked seemed to have thicker mica than the Blackburns and Seimens. I should have noted the date and such but I was pre occupied with the "teeth " thing. So much minutia,so little time! :BEER Bob

jcs
11-14-2008, 06:55 PM
hey jeff,thanks for the info and links!

Jeff West
11-16-2008, 09:17 PM
Hi J&B- FWIW I have an amp here handy that has a couple of '59 I61s with shield logos, I pulled them and the "B9F" has all the teeth on the top and a "B9L" does not. I'll maybe get around to looking at some others at some point.
Incidentally, both of the above have the silver/plated grid rods poking above the top mica, the rods went back to bare copper very shortly after that December one.

JW