First, about the ECC802S tube

Around 2018, there was a sudden surge of interest in the rare Telefunken ECC802S. This tube is internally different from the standard Telefunken ECC82, which meant fakers couldn’t simply rebrand ECC82 as ECC802S without being noticed. Prices jumped to about 150 euros. At the time, everyone thought that was outrageous.

Now, as I’m writing this in 2025, these same tubes easily sell for around 350 Euro "as is" on Ebay, or 500 Euro when guaranteed to be good, with detailed test data included. Such a price increase may sound like a dramatic increase, but it actually reflects a fairly typical yearly rise of around 20% per year, which is normal for highly sought-after NOS tubes.

Ift the trend continues, the Telefunken ECC802S will be around 1,240 euros in 2030. I’m sure there will be more people saying, this is crazy. Just give it time.

Telefunken G-73R

So what exactly is this tube? I can’t say with certainty. Is it an ECC802S or ECC82? Or perhaps an American tubes?

One very interesting way to research something like this is to use Google’s date-restricted search. Looking only within a specific time frame. It lets you see how information developed over time. And when you do that, you’ll notice something curious: the G-73R suddenly starts appearing around 2015, usually with handwritten numbers on the glass.

Before 2015? The internet is completely silent about the G-73R. Nobody reported discoveries, no foam boxes filled with dozains of tubes, nothing on Ebay, -- absolutely nothing.

I’m not very interested in social-media “information,” because none of it has real sources--it’s just the same claims repeated over and over. For example, a seller in Asia insists his tubes were made for Agilent, which is impossible since Agilent was founded long after Telefunken stopped production. He’s been selling the same pair for years, always claiming he “just found one more,” along with stories about medical and aviation use.

The stories continue with the tube’s coating. Everyone has their own guess--better shielding, special screening, and so on. Yes may be. And may be not. Without facts, it all goes into the drawer of unconfirmed ideas.

I was send the above picture by email, but it is the only picture I have seen. Indeed it would be easy to put the first fake ever, in such an empty box, and then sell more fakes. I do not say it was done like that, but I do say it is possible.

The box itself actually looks quite authentic. I worked at Hewlett-Packard in sales for 11 years, and I remember selling semiconductor diodes like the 5082-2811. Those were internal part numbers from HP’s very old numbering system, which was replaced in the 1970s by the newer “H-” system. For example, HP’s early LED lamps used part numbers like HLMP-1000 (“LMP” for lamp), and optocouplers were labeled HCPL-xxxx. Older parts simply kept their original numbers.

What we can say, this tube here, if it is not fake, was from before 1970. And no, it was not made for Agilent. On this box, it writes this is an aged 12AU7.

So what is the G-73R

Now im 2025, we got a lot further. Olaf M. from San Francisco send me a copy of the Hewlett Packard manual of the 410B tube voltmeter. There are six versions of the manual around, and only one refers to the G-73R. Now, theoretically someone could have faked this manual to promote sales, but this is probably not the case. Because so far, as re-write this text part in November 2025, nobody referred to it.

The 410B manual gives indeed this part number G-73R, saying it is a 12AU7 (=ECC82), selected for performance. Now that is really something.

What else do we read.... A normally good (EIA standard) tube will make the instrument work good, but G-73R will make it work better. The position is V2 and V3.

Here is a picture of V2 and V3 in the 410B, and what do we see? V3 is a "Hewlett Packard" re branded tube. On V2, the Telefunken logo is visible. What else do I see? tp me it looks like an ECC82, and NOT ECC802.

The application

More information is given by the calibration procedure. Five items are important.

Item 2 writes about low microphonics and better DC stability. This brings us to the schematic.

In the schematic we see, the "Zero Adjust" potentiometer. I have a Philips tube voltmeter, and it also uses an ECC82. I have the original tubes in there, and indeed the zero adjustment is something which needs to ne done regularly. I can confirm this, and you can bet Philips used their own very best tubes in the volt meter. Selection makes a lot of sense. Aging also makes sense, because what's the use if a tube is initially good, but becomes in stabile later. Or a tube is in stabile initially, but develops stability after aging. It is rather so, that the stability of this ECC82 defines the comfort level of the volt meter.

The black paint

The the black on the picture is missing. This is strange. If that painting was so important for shielding and whatever people came up with... Then why does Hewlett Packard picture it's 410B without it?

What is in favour of the black paint, is the picture which somehow seems genuine to me. But that is my gut feeling, I can't prove it.

Call for information: Perhaps someone has an manual of the HP equipment, using this tube? This would PROVE this tube existed indeed. All I see here, is a sticker, which I can produce myself with photoshop as many as I need. Please let me know if you have additional information which has hard facts. I will be glad to add it here, or make corrections to the text now written here, if needed. I try to stay with the facts in this article. Please do not write me about texts which you found in social media by anonymous writers, who do not give a source reference.

G-73R. The easiest to fake tube

I keep the option open, many G-73R on the market today, are well done fakes. One thing is sure: This is the easiest to fake tube for amateurs. Any used TFK ECC82 can be used for it, since the tube was 'aged' anyway. The black paint can be done by anyone, it hides whatever is inside. Just the original boxes, as you can see pictured here, they are missing of course. That is where the plastic bulk packs come in the game. With NOS, boxes are sometimes gone, with 20% or so of the tubes. But with G-73R... they are always, always gone. Very strange.

There is something else elementary wrong with 'Labormuster' Stickers I see. These stickers existed indeed, that is true. But it makes no sense for the G-73R. Let's put the puzzle pieces together for this.

Experimental prototypes

The German word Labormuster means: experimental prototype. When I search some internet pictures for this, I find tubes like that. Many are uninteresting tubes, like from the P-Series. This brings me back to Hewlett Packard, my ex-employer. At the beginning of the story, ist that Hewlett Packard box. The only reasonable reliable picture I know. So the Hewlett Packard designation is 5082-0406, and the Telefunken designation for the same is G-73R. So far so good. Now just imagine the situation at HP. They sold this tube in their measurement equipment. The make not just something. Performance of this tube, combines with a precision panel meter, form the core of the instrument. Do you really think they use "experimental prototypes" for this? I don't! That is out of the question. I have a copy here, of what is called the 'environmental manual' by HP. It describes in detail how products are qualified. Before a 5080-Part Number is assigned, products must pass painfully precise procedures. HP was famous for that. 100% sure. Imagine someone dies from this. The instrument if suspected, gets opened and out come.... experimental prototypes. I worked at HP also 2 years as an auditor at HP Medical, and I can tell you first hand, No, they would never do that for medical products. Any auditor would have picked such a product out. For a product like a voltmeter, it's a lower control level and perhaps yes they would allow it, but it stays weird because failures with the instrument caused by HP itself, can become expensive in some countries. HP is in trouble if the instrument causes severe damage, and experimental prototypes are found inside. So I tend to believe these stickers are a faker's mistake.

From the same seller from Asia, I see such stickers with clear visible traces of digital printer pixels on it. I am not surprised. I see more evidence of faking with this seller. Such as CCa tubes, labeled CCA., and printed with new, thick paint, instead of printed with this original white ink which is water solvable, and wipes off easily. His auctions have several faked products, that is certain. Not that I care much about this faker, it is just that I saw faked stickers of G-73R on his website.

Finally, someone asked an ex-Telefunken tubes sales person, who is now retired. He said, he never heard of G-73R. Not remembering it, is something else than saying: no we never made it. In any case this is what he said, and it is an information piece. I also met this person a few times, and I can tell you he has an excellent memory.

Conclusions and questions:

1. Yes, G-73R existed, if we can believe this one catalog. Five other catalogs do not mention it. Anyone with a color printer can make such stickers, and buy black spray paint in the super market. Some others write the tube number on it by hand, with a silver pen, as if Telefunken worked like that, and as if Hewlett Packard would accept this.
2. We just would need to see a few more of those original boxes. Why are these ALWAYS gone? That is VERY suspicious.
3. In the past, there was no G-73R offered at all, until in the year 2015 suddenly someone had a pair with a story. And then another one had a pair with a story, and another and so on. And now, when you look for images un Google, the internet is full if G-73R, the easiest to fake tube there is.
4. An Asian seller I have seen definitely seen offering fake tubes of other part numbers. He a mistake with the part numbers. This person always 'finds another pair' G-73R wich is the last, and he finds them since a few years.
5. Why does Hewlett Packard picture the tube with clear glass and Telefunken logo on it, and no black paint?
6. Why do no other brand G-73R pop up? Hewlett Packard does not write it has to be Telefunken.