Fake valves...

[Nick]

Probably been seen here before - good information, though...

http://www.vacuumtubesinc.com/VacuumTube...Shame.aspx

[Radio Fixer]

Interesting site as well Nick.

thanks Gary

[Yorkie]

Interesting site - thanks for the link Nick.

Those valves look very authentic, and I guess that even with a valve tester, some wouldn't show up as anything but genuine. EG, the '80' rectifier - really a 5W4G tube put on a 4 pin base, would test fine, but only has an output of 300mA rather than the 400mA of a genuine '80'. Maybe in some applications that wouldn't matter, because 400mA is a hefty output. A knowledgeable valve aficionado would notice the difference in the size of the bottle too.

There are some 'fake' valves that are fine in the electrical sense but not in terms of physical dimensions. The best example I can bring to mind is the EBL31s that have been on offer from reputable UK valve dealers for years for £25.00+, but which are actually EBL1 side contact valves with an octal bases fitted over the side contact base. That's neatly done, and may even have been done at the factory, but they're not the genuine article, though I'm sure they weren't converted with any intention to deceive, but as an expedient due to the lack of genuine EBL31s.

The EBL1 and EBL31 are electrically identical and have the same sized glassware, but the converted EBL31s are 1" taller and are too tall to fit into an Ekco A22, to allow the back to fit on, though in most sets calling for an EBL31, it wouldn't matter. The converted EBL1s are easily spotted as they have a tall octal base with a join where it meets the original still fitted side-contact base, and also have a 3/8" top cap rather than a 1/4". They can be reduced in height, which I covered in a BVWS Bulletin article, but it's not a task for the faint-hearted. The pic attached shows the clear differences.

[pwdrive]

I wouldn't fancy trying to pull a continuous 400 ma DC output from an 80.

Lawrence.

[AlanBeckett]

I don't think you'd manage it.
As far as I can tell from the available Data the Peak Anode Current is quoted as 400mA but the maximum Output DC Current is only 125mA.

Alan

[pwdrive]

That was the point I was making Alan, in a sort of diplomatic way.

I don't think I have anything with an 80 in it, only an 83 which is a mercury job.

Lawrence.

[AlanBeckett]

Lawrence,

Actually I do, but it's in an ancient American Valve - sorry Tube - Tester.
However, I can't imagine that it ever needs to supply a great deal of Current. I suspect it was just what was readily available at the time.
I have a NOS spare. Do you think I should cash it in?


Alan

[pwdrive]

Yes, stick it on Ebay, tell them it's got it's original vintage vacuum.

The 83 mercury vapour job I have is also in a valve tester, it was working last time I tried it.

Lawrence.

[Nick]

...vintage vacuum...

I like that concept - by definition, vintage "nothing".

The idiots on eBay would pay a fortune for that.