Noisy NOS Telefunken tubes

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AusTex64

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Jun 3, 2013
Messages
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I have three Telefunken tubes purchased for some mic builds that are all very noisy. Which really surprises me, I've never had this happen with Telefunken tubes before. I have another Telefunken tube of the same type that is quiet and sound great in my builds, so I know it's not the mics. I suspected that first, so checked tube socket tension, cleaned all components, cleaned tube pins, etc. The noise follows the tubes.

So, is there any procedure for burning in these tubes to eliminate the noise? Or do I just pitch them and get more? Just seems odd that all 3 have this problem. Unfortunately I've rubbed the date code off the tubes by handling them, but I'm guessing they are quite old based on the packaging.
 
run them 100 hours or so first.  RDH also lists some tube burn in procedures, and there are some other threads here too. 
 
I bought these tubes from Oliver Archut, they are original Telefunken tubes in the factory packing, never opened before me. I have purchased at least 100 Telefunken tubes in the past. So while I'm no expert, I have seen numerous examples of original tubes and packing over the years. A reasonable concern, though. That's why I always buy from reputable, known sellers. It's worth a little more not to get jacked by bogus goods.
 
Doug, thanks for the advice. I will burn them for at least 5 days straight. Was about to buy 8 more tubes to try. Perhaps I need to be more patient. :)
 
Interesting. What tube models are they? I have some pf 86 Telefunken tubes that seem to be hissy also. I need to trouble shoot, but seems like tube noise to me. Burned in for many hours.
 
Check the Morgan Jones book. There's some text in there on commissioning old tubes that have been in storage for a very long time. I don't remember the exact details, but it is a several hours relatively low temperature bake in your kitchen oven followed by running heaters only for 30 or 60 minutes and then bringing up the B+
 
Matt, thanks for that info!

Here's a link to a Morgan Jones paper addressing this: http://www.vacuumstate.com/fileupload/Baking_valves%20pix.pdf
 
AusTex64 said:
Matt, thanks for that info!

Here's a link to a Morgan Jones paper addressing this: http://www.vacuumstate.com/fileupload/Baking_valves%20pix.pdf
Ah great - that is much more detail than he provides in the book I have. More people need to know about this. Starting up the old valves (Even on a tester) before baking can lead to cathode poisoning. Bowie needs to know this. I did tell him once but I don't know if he adopted this practice. Seems a shame to potentially ruin good valves by not doing this.
 
Baking audio tape.

Baking guitar soundboards.

Baking vacuum tubes.

Perhaps even the odd bread and pizza, while we're at it.

Is there anything we shouldn't bake nowadays?



;)



Yup, interesting stuff.

Keep it coming.
 
I used to like to get baked. But that was in the 80's. 😎

I'm gonna try this baking thing on my noisy mic tubes and will report the results.
 
AusTex64 said:
I used to like to get baked. But that was in the 80's. 😎

I'm gonna try this baking thing on my noisy mic tubes and will report the results.
OK. But I think you get the most out of it if you need to do it before using the NOS tubes at all. Once they've been fully powered up there is less scope to improve things by baking.
 
<OK. But I think you get the most out of it if you need to do it before using the NOS tubes at all. Once they've been fully powered up there is less scope to improve things by baking.>

Agreed. But there's nothing to lose at this point by giving it a try. These three tubes are useless as is.
 
Baked three tubes for 12 hours at 130C. Used a temerature probe to attain accurate temperature in my home oven. No change in noise. But the cathodes might have already been polluted by me trying to burn them in the mics first, before finding out about this procedure. They ran for at least three days straight beforehand.

I have one good tube though. It is was always good from the get go. I inspected it closely under a magnifying and nited some construction differences between it and the other three Telefunken tubes.

I have 12 more tubes on the way. Six each Telefunken and Mullard. Gonna bake all of them before trying them in the mics.
 
Bought six Telefunken EF86s from a reputable dealer.
All six useless.
Switched to the Philips family.
Now we're talking.
Some pretty darn nice tubes used to come from my country (and foreign factories owned by Philips).
Those were the days.
 
micaddict said:
Switched to the Philips family.
Now we're talking.
Some pretty darn nice tubes used to come from my country (and foreign factories owned by Philips).
Those were the days.
The best valves (tubes) in the known universe came from the huge Mullard factory in Blackburn, UK

But Mullard was Philips, UK for a loo..ng time.

It was one of the reparations demanded by de Ruyter for removing his fleet from the Medway  ;D
 
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