Tube ID Question

[xStonr]

I recently was able to get some NOS tubes. These tubes came out of a shop that did electrical repair and has not been in business for many years.

The tubes are labeled Dumont and are 12AX7a. I'm having trouble finding any info on these tubes but Dumont probably is only a reseller and the tubes are made by someone else. There is some other writing on them. Dumont is in red and the other writing is in red also. Written is 30-62 which is underlined and below the line, 158 is written. And written vertically is ABD. Written in red and grey is made in USA and also 12AX7.

The box is gold with black writing and a with circular graphic.


Any info on these tubes would be appreciated. Thanks

[mojo2001]

Steve:

Dumont repackaged those tubes.

Some of the Dumont tubes I have seen were actually rebranded Mullards and Amperex.

Admiral branded tubes are also good stuff--mostly European.

The way the numbers are etched onto the glass should give a good hint as to manufacturer, because this was typically done at point of production.

[JimiBryant]

look at the markings for the tube types.

if they are inside of an octagon then it's of RCA manufacture

the letters U.S.A. under the tube designation generally indicate a Phillips/Sylvania tube.

GE tubes all have this odd little pattern of dots which, once a person recognizes 'em, will
allow one to spot any GE-manufactured tube from that point onward..

that's it for domestically manufactured tubes, I think?

many times re-brands were due to one company owning another or being sub divisions of
a large conglomerate (RCA and Zenith/Admiral being one example) and other times due to
a bulk purchase under contract.

Dumont probably sub-contracted from various suppliers so they could
be just about anything. I've seen RCA-branded Amperex 12AX7s, so
anything is possible. apparently, re-branding was very common in the
1940's and 1950's.

[xStonr]

Here's a quick shot I took of the tube. Excuse the size.

[51Esquire]

The 30-62 is the date code, which is the 30th week of 1962. As I remember, the ABD is the warranty expiration code. You needed a chart to figure that one out. I remember counter men at the parts houses had them at the counter. I'm dating myself!

The 158 is the DuMont EIA manufacturer's code.

[mojo2001]

How about a pic of the etched tube number...looking like a Sylvania to me.

[xStonr]

How about a pic of the etched tube number...looking like a Sylvania to me.

You are correct sir!

From my other "research", the consensus is that they are Sylvania short plates.

[mojo2001]

Thought so...that's the benefit of wasting my youth looking at tubes!

[Opaltone]

Originally Posted by xStonr

You are correct sir!

From my other "research", the consensus is that they are Sylvania short plates.

Indeed! From 1957 or 1958, not '62. Sylvania made these short gray-plates for only one year, then went to their long-plate 12AX7. Sylvania is the only "golden years" manufacturer I know that went from long (black) plate to short (black in '56, gray in '57/early-'58), then long (gray) plate 12AX7.

- Thom