Packard Bell 12ax7a... is it an RCA?

[T-Dogg]

I have a particular "Packard Bell" labeled 12ax7x tube... Really like it, but its gone somewhat microphonic. I'm looking to find similar, but so far haven't seen anything matching its specific plate construction. I've read many Packard Bells were rebranded RCA's - does anyone know if this is the case for all of them? This one doesn't have the typical RCA- border style around the 12ax7, somewhat long gray ribbed plates with only one square hole cutout in the middle of each side... I could try to take pics, though much of the label is now missing.

[Alexo]

I assume this is a Made in the USA tube? Not having the stop sign logo suggests Sylvania, particularly if the "12AX7" is acid-etched in the glass and won't flake off. If it has large letters for the "12AX7" with little dots around it, it would be GE. A pic would help identify it... meanwhile, you might be able to find a look-alike here http://www.tubemongerlib.com/gallery2/main.php

[dotfret]

It is something of a shame, the long plate designs sound better than the short plate designs, but the fact that they "go microphonic" is the reason why most makers went over to the short plates.

only one square hole cutout in the middle of each side...

I take it you are talking about the "stitch holes" that hold the two plate halves together.

Go to the reference Alexo gives above, and check out the CBS 12AX7 valves. Is it like one of those?

[leslie]

Some Packard Bell and Emerson like these ones are made by Sylvania , so you can compare with yours...
http://i41.tinypic.com/14sjsc0.jpg

[dotfret]

I've read many Packard Bells were rebranded RCA's - does anyone know if this is the case for all of them?

I've been doing some research recently - Packard Bell were part of the Raytheon group in the 1960s.
As far as I can determine, Raytheon sold off a lot of plant to GE and outsourced much of their tube supplies from 62 onwards to Raytheon factories outside US, and other US suppliers.

Also "as I understand it", those dot-coded GE valves were produced on lines that GE bought from Raytheon - any body like to confirm or deny that?
I know I'm a yoyo, so don't be embarassed about telling me that I elocute from my anal orifice - I'm guessing, but finding the real info is like getting blood from water.

To me, that "one hole up the side" says CBS. Anybody got another idea?

[digbystar]

Hi, I'm new here , first post ever. I had to chime in. My uncle past away a month ago and in his stuff was a Sylvania tube caddy. I grab some what I think were used Packard bell 12AX7's. I can't believe how good these sound. I though I was smoking too much crack that day, but I keep coming back to them.
If anyone can find them I will take some too!, Digs

[novemberrain]

Also "as I understand it", those dot-coded GE valves were produced on lines that GE bought from Raytheon - any body like to confirm or deny that?

Raytheon 12AX7s were built on tooling sourced from Europe, their internal construction is identical to Amperex. The glass envelope was made on tooling dissimilar to Amperex, probably U.S. sourced.

GE was manufacturing 12AX7s on their own tooling in 1957 and continued to do so.

A peculiarity of Raytheon 12A-7 type tubes is that they frequently have the tube type printed on top of the tube around the pontil, no other maufacturer did that.

Manufacturers went to short plates to reduce inter-electrode capacitance which makes the tubes more suitable for RF applications.

[digbystar]

I just pulled mine out to try and get a picture of it , but I can't get it to take(stupid auto focus). But the date code is 60-17 and 274 which I think is RCA. long black plates too, Marked 7025

[digbystar]

[dotfret]

Yes, 274 = RCA

Now, closer to the original question - I went and looked in the big box:

I have some long black plate Sylvania JHS 12AX7, which look very similar to the valve pictured above, except they only have one stitch hole in the side, not two.

Example 1 - etched marks 12AX7 over L4V, labe reads JHS 12AX7 over MADE IN USA over SYLVANIA and an EIA code 507.

Example 2 is in an original "military supply" box, which indicates "MFG BY SYLVANIA --- PKD. 1-61" and "SIMILAR TO THE CV-492". Etched marks 12AX7 in a smudgy stop sign box over L1T, labe reads JHS 12AX7 over MADE IN USA over SYLVANIA, and an EIA code 238.

Exanple 1 shows typical Sylvania etched markings, example 2 does not, but the box says it is probably right (I have another similar).

So right now I am guessing the first valve asked about is a Sylvania, and also that I have found two more EIA codes to tentatively add to the list.

[Chappy]

Yes, 274 = RCA

I have some long black plate Sylvania JHS 12AX7, which look very similar to the valve pictured above, except they only have one stitch hole in the side, not two.

Example 1 - etched marks 12AX7 over L4V, labe reads JHS 12AX7 over MADE IN USA over SYLVANIA and an EIA code 507.

Dotfret
I went and had a look at some of my old 12ax7's which are pulls from one large piece of military hardware.

I have a long black plate Sylvania tube with the following markings

12AX7 (underlined)
A4J underneath

On the side it has
12AX7
Made In USA
Sylvania

code 424 beside that

What is interesting is that the plates inside this tube are physically identical to the plates inside some RCA tubes that came from the same hardware. All of the tubes have a small scratch on the side of one of the plates (possibly a quality assurance check mark?) The base of the tubes are slightly different though. The Sylvania tubes have a small circle pattern in the base on the inside of the glass. The RCA tubes do not. It looks to me like Sylvania and RCA were sourcing the same plate parts.

Chappy

[dotfret]

Well, thanks for those details. Another number for my list - I have to revise it again.

I looked at those Sylvania of mine again, and yes, they have a mark in the base glass - but I would describe it as a letter O shape - it is not circular.
That might be a useful telltale, but I don't have much to compare with. These Sylvanias are the only US blackplates I have. I do have some contemporary Sylvania 12AZ7, but none of those show that O mark. Then again, those are the lighter "standard" glass envelope, whereas the JHS 12AX7 appear to have a thicker "rugged" envelope. And the writing is pale green, not yellow - shd've mentioned that before.

I only own one other blackplate, which is a Brimar. Everything else I have in the long plate style is grey and European - only Brimar made blackplates in GB, and not many of those.

I don't think RCA would be sharing components with Sylvania - anyway, look at that RCA pic above. Two stitch holes each side holding the plates together - only one on the Sylvanias I have. RCA did occasionally buy valves in from Sylvania, but more often they bought from Mullard when they were short of stock.

Then again, when all is said and done, I am just an old limey.
Go back 40 years and there were 2 kinds of valves in GB. There were Mullard valves, and valves you used until you could get a Mullard to replace them. Well ... RCA and Philips - you wore those out, then you replaced them with Mullard. Other makes were for radios, TVs and gramophones, not serous pro applications like guitar amps.
Honestly, in the "way back when", I can remember replacing an input valve of an AC30 in the music shop for a customer who was waiting, when the repairman was out to lunch. I went for a new one off the shelf - there were only Brimar and Philips in stock. I switched the dodgy valve for a Philips, and HID THE BOX as I went back to the counter - so embarassed it wasn't a Mullard.

[TimbreWolf]

What is interesting is that the plates inside this tube are physically identical to the plates inside some RCA tubes that came from the same hardware. All of the tubes have a small scratch on the side of one of the plates (possibly a quality assurance check mark?) The base of the tubes are slightly different though. The Sylvania tubes have a small circle pattern in the base on the inside of the glass. The RCA tubes do not. It looks to me like Sylvania and RCA were sourcing the same plate parts.

Sylvania black-plates are shiny, whereas RCA black-plates are relatively dull (non-reflective). Raytheon black-plates are also shiny, too, like Sylvania. You can tell them from Sylvania plates by looking at the plate tabs, as they emerge from the mica: squared-off/one cut = Raytheon, angled/rounded/3-cuts = Sylvania.

- Thom

[Alexo]

Also "as I understand it", those dot-coded GE valves were produced on lines that GE bought from Raytheon - any body like to confirm or deny that?

Raytheon 12AX7s were built on tooling sourced from Europe, their internal construction is identical to Amperex. The glass envelope was made on tooling dissimilar to Amperex, probably U.S. sourced.

GE was manufacturing 12AX7s on their own tooling in 1957 and continued to do so.

A peculiarity of Raytheon 12A-7 type tubes is that they frequently have the tube type printed on top of the tube around the pontil, no other maufacturer did that.

Manufacturers went to short plates to reduce inter-electrode capacitance which makes the tubes more suitable for RF applications.

Welcome back, NR, nice to see ya 'round these parts again.

[Chappy]

Dotfret

Your description is more accurate, it is more of a letter O than a perfect circle on the bottom. All of my tubes have only one `stitch hole` on the sides though.

Timberwolf

I checked my tubes again, and you are right about the dullness of the RCA tubes. The getter rings look like they are attached differently also. The tabs which extend through the mica have rounded corners on the Sylvania tube. The RCA tubes seem to have a mix of rounded and squared of corners, but the rounded corners are more subtle. Finally the ribbing on the sides of the plates are a bit different. The Sylvania tube`s cross members overlap the vertical members whereas they don`t on the RCA tube. I stand corrected on my previous post. The plates look very similar in physical construction but they are not identical. Thats what I get for examining tubes while drinking Vodka!

Chappy

[TimbreWolf]

Timberwolf

I checked my tubes again, and you are right about the dullness of the RCA tubes. The getter rings look like they are attached differently also. The tabs which extend through the mica have rounded corners on the Sylvania tube. The RCA tubes seem to have a mix of rounded and squared of corners, but the rounded corners are more subtle. Finally the ribbing on the sides of the plates are a bit different. The Sylvania tube`s cross members overlap the vertical members whereas they don`t on the RCA tube. I stand corrected on my previous post. The plates look very similar in physical construction but they are not identical. Thats what I get for examining tubes while drinking Vodka!

Chappy

The closer you look, the more you see. Don't look too closely, though, because then things get all quarky, and you discover its all only your own reflection, peering back at you

- T