WE12 (WE12) - Similar or equivalent tube (EM4)

Tube administrators,

The Funkschau 17, Jahrgang 1944 - Heft 5/6, Page 6 of 6 which addresses the subject of the WE Italian Tubes  . . . . . .the tabular data identifies in the 3rd column the tube WE12 as "Corresponds to the Red tube or Philips--- EM4.

The WE 12 tube data sheet identifies as Similar Tubes only the Telefunken EM11 and the EM5.

Should the Similar Tubes be expanded to include also the EM4??

This inconsistency was noticed recently AFTER I had advised an RMorg member that the EM5 tuning indicator would be the most appropriate "substitute" if he could not locate the original WE12 tube.

Respectfully,
Robert Sarbell

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Dear Robert

Our tube pages are far from perfect - it is the last big activity we have introduced. we are glad for every hint where to improve our database.

You are right, the EM4 is best choice for a WE12. I would not say it is the same - the form for instance is a bit different and our data sheets show uncertainity for telling they are equal. But I would say the possible differences are so small that we can agree to the smallest difference we can notate.

I did put it into "normally interchangeable" - even when some books say equal - which is in our understanding not true.

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Dear Ernest,

Thank you so much for the prompt reply. When discussing the replacement for the WE12 tube in the Telefunken T5 radio (in some recent discussions between several RMorg members), I had advised that the EM5 was most appropriate.

However, the choice could be somewhat arbitrary. . .whichever the owner prefers.

Nevertheless, I sent a new EM5 to the member.

Respectfully,
Robert

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Apparently Telefunken didn't intend to introduce their all-metal E11- "steel"- tube line into Italy. 

Instead they introduced some special P8- side-contact-base glass tubes with the same characteristics as their respective E11- "steel"- tubes for the Italian market.

The "steel" ECH11 triode- hexode frequency converter became the P8-base glass tube WE20, the sharp cut-off penthode EF12 became the glass WE17, as well as the magic eye EM11 became the WE12.

In 1951, Telefunken introduced in Germany also a P8-base version of the EM11, the EM5, with considerable smaller bulb diameter, to compete with the EM4. Hence, both the WE12 and the EM5 are P8-base versions of the EM11, they only differ in their bulb diameter.

Short after the EM5, an octal version of the EM5 was introduced, the EM35, to compete with the EM34, which in turn is an octal version of the EM4.

Although the EM4 and the EM5 have different indicating patterns, they are interchangeable. The same is with EM34 and EM35 as well.

For those who understand German, see more about the WE- tubes in my article "Einige Kuriositäten und Exoten", particularly at post 4.

Best Regards,

Jacob

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Dear Jacob,

Without knowing the actual physical dimensions of the WE12 glass envelope, it appears as though there coiuld be some "mounting differences" if the smaller diameter EM5 tube is placed in the opening for the WE12 tuning eye.

From the photo of the WE12 tube, it appears as though the diameter of the tube (and not necessarily the "eye"), is identical to the EM11 - or the EFM11 as I have in my 1938 SABA 455WK.    

If that is so, then a WE12 tube should be replaced with only another WE12; or add some type of collar around the top of the "replacement EM4 or EM5" tube.

Respectfully,
Robert

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Hello Robert,

Here   U we can see the physical dimensions of the eye tubes EM5, EM11, UM11, EM34 and EM35.

The diameter of the WE12 bulb is 37 mm, which is same as of the EM11 (or EFM11 and EFM1 as well).

The diameter of the EM4 is 28 mm, same as for EM34 / EM35, while the EM5 has 31 mm, same as for AM2 / C/EM2.

Sure, the smaller diameter of the EM4 or EM5 may cause problems by using them as WE12 replacements, depending, how the WE12 is attached in the set and depending on the design of the "window" to watch the eye tube.

In some cases it may be easier to replace the WE12 by a cheaper russian 6e5s, particularly, since EM4s, EM5s or even WE12s are more or less elusive to get these days.

Best Regards, Jacob

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