Telefunken or not Telefunken, that is the question

[gadget73]

I have a set of EL84 tubes in my console marked Hoffman, made by Amprex. They also say Made in Germany. I thought Amprex tubes were from Holland? What sort of codes or other info would I be looking for on the tube to determine if it is actually a Telefunken or if its an Amprex?

 

[Stephen J]

Turn them..

..upside down.
Look in the center on the bottom,surrounded by the pins,is there a diamond shape in the glass ?

 

[Bluelobster]

I have a set of EL84 tubes in my console marked Hoffman, made by Amprex. They also say Made in Germany. I thought Amprex tubes were from Holland? What sort of codes or other info would I be looking for on the tube to determine if it is actually a Telefunken or if its an Amprex?

The way to tell for sure is to look at the etched date code on the bottles. The information is readily available on the 'net.
Phillips, who owned Amperex (as well as Mullard, Valvo, Osram and Sylvania) had plants in West Germany. If it is only marked Germany, I'd be willing to say it was made by RFT or another iron curtain manufacturer. Not that it is a bad thing, they made some good tubes we have come to find out.
Perhaps you can identify it by comparing it here.....
http://www.tubemongerlib.com/gallery2/v/EL84/

 

[gadget73]

codes on the bottles:

8-37



KM2
=8D (the = sign also has a | through the middle of it)

on the bottom, in the middle of the pins is a 28, no diamond.
?

They look like the Valvos in those pics, but they also look like the Brimar and the Bangalore tubes. Some looking tells me Seimens and Tungsram used the "not equal" marking ? Another site tells me these were made in Blackburn, but that doesn't jive with the Made In Germany printing. The description of the plate structure also doesn't jive with what I'm looking at.

 

[Bluelobster]

codes on the bottles:

8-37



KM2
=8D (the = sign also has a | through the middle of it)

on the bottom, in the middle of the pins is a 28, no diamond.
?

They look like the Valvos in those pics, but they also look like the Brimar and the Bangalore tubes. Some looking tells me Seimens and Tungsram used the "not equal" marking ? Another site tells me these were made in Blackburn, but that doesn't jive with the Made In Germany printing. The description of the plate structure also doesn't jive with what I'm looking at.

Here is a link to the code I googled, you can wade through it. There are other links to compare if you look.
A quick glance shows that the =i is the manufacture code for Siemens and Halske. Hence the "made in Germany" label. I didn't see anything to denote Tungsram. Not gospel but any tube I saw made outside the iron curtain had "West Germany" on it.
http://www.audiotubes.com/mullcode.htm

 

[5AR4]

I have a set of EL84 tubes in my console marked Hoffman, made by Amprex. They also say Made in Germany. I thought Amprex tubes were from Holland? What sort of codes or other info would I be looking for on the tube to determine if it is actually a Telefunken or if its an Amprex?

The brand name often has little to do with who made the tube. I have a couple of quads of EL84 branded Tung Sol that were made by Brimar, a quad of Phillips EL84 that are Mullard, Sylvanias made by Phillips (Amperex was simply Phillips' US marketing brand before they bought Sylvania) and some GE-branded EL84 that are also Mullard.

I have a quad of NOS Brimar EL34 that are Mullards.

Bluelobster is correct, the "unequal" code is Siemens. What follows the "unequal" sign is the date code.

They all sold each others' tubes. As an example of that if you see the famous red-based 5692 those were *always* made by RCA, but you'll see them in Sylvania, GE and many other brands. Ditto EL34s. I cannot think of a single brand that didn't sell relabeled Mullards at one point or another, including brands that aren't known for "high-end" audio tubes like Zenith or DuMont. And my namesake tube, the 5AR4/GZ34, were almost alaways made by Mullard regardless of the brand on them. I do have a couple of very early ones that were made by Phillips in Holland but those are kind of rare. Later Sylvania, Matsushita and GE also made versions but probably 90+% are Mullard.

True Telefunkens miniature tubes always have a diamond between the pins. Later on they sold Siemens with the Telefunken label on them. But guess what? All the Telefunken 5AR4s I've ever seen were Mullard.

Also, another thing to be careful of: as the US manufacturers wound down production they started bringing in Russian tubes (yes, the ENEMY at that time!). I just saw a quad of EL34s that were either Russian or Japanese (could not tell from the photo, but the guidepin did not have the telltale Mullard hole in it) that had "Made in England" on them go for close to $400 on eBay. Whoever bought them obviously thought they were getting Mullards. They weren't.

On that note, if you ever see "Made in England" on a tube beware. Mullard and the others always said "Made in Great Britain". Raytheon in particular was bad at that but they all did it. I've seen people pay big $$$ for 6L6GC tubes that are clearly Russian if you know what to look for because they were branded Raytheon and had "Made in England" on them. I've seen EI tubes called "Amperex" and sold for lots of money.

TMI? Sorry, I've been collecting tubes for years.