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Tube - NOS - crackle/popping sound through headphones at first warm-up

post #1 of 5
2/3/12 at 4:16pm
Thread Starter 

Hi

 

Got some NOS Tung-Sol 5998 tubes ("Tests as new") for the WA2.

 

Plugged them in.

 

Turned on power with headphones on head and plugged in. 

 

One VERY loud crackle noise (like lightning...) through headphones.

 

Unplugged headphones and kept amp going. Went back 30 minutes later and inserted headphones. Music played, then suddenly another similar crackle/popping noise, then normal. 

 

I emailed seller, who told me I had to remember that these were NOS.."....well you have to remember that these tubes have not been operated since manufacture many, many years ago. Normally the cathodes will burn off any residue from manufacturing over the first 50 hours, and emissions will reach close to steady state at that point. Give them at least 24 hours of run time. ...."

 

Except for the two very loud crackle noises I haven't heard anything (but I aven't been listening fro more than a couple of hours)

 

The tubes look normal (no flashing, blue light, no noises) and are dead silent. They act as excellent tubes.

Were the first crackles due to some gas burn off, release of static electricity or something, and can be prefectly fine - or should I return the tubes?

 

 


Edited by ardilla - 2/3/12 at 4:19pm
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post #2 of 5
2/3/12 at 4:29pm

Hmmmm...couple possibilities.

 

One, the pins might be dirty.  Did they look clean? If not, you should take some 0000 steel wool, or a wire brush, and chean them gently, and then put on some deoxit.  This is a good regiment to always do with tubes.  Just make sure there is no residue from the steel wool after cleaning.

 

Second, the tubes might not be seated correctly in the sockets.  Make sure they are.

 

Third, and most problematic, the tubes might be arcing.  That would mean they are bad.  If you ever see any sort of spark or flash of light in the tune when you hear the pop, you know you are in trouble,  an arcing 5998 can take out your headphone driver, and possibly your hearing.  I lost a DT990 driver due to an arcing tube, and it's just lucky that I wasn't wearing them at the time.

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post #3 of 5
2/3/12 at 4:51pm
Thread Starter 

Thanks :)

 

So you exclude my theory that the first crackles were due to some initial gas burn off or release of static electricity?

 

There have been no pops, only to single loud crackles that came the first 30 minutes... I let them run for 15-20 hours total, and been listen 4-5 of them - no pops or crackles - only good acting tubes - dead silent, no issues.  

 

What would you do - return them to the seller and risk getting a pair with other issues (noisy, icrophonc etc), or keep them if they continue to act good - they seem to have acted perfectly after the first warm up ?

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post #4 of 5
2/3/12 at 5:35pm

I've never experienced NOS tubes doing what you described only when first used.  It's usually the sign of a tube going bad in my own experience,, but I suppose it's possible.  If you never get another pop, then you may be fine.


Edited by Skylab - 2/3/12 at 5:36pm
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post #5 of 5
2/3/12 at 7:14pm

Happened to me on some GE 6AS7, seller description was NOS but all three had some kind of noise and spark, one was so bad it didnt stop flashing and it was the first to test and the mothercracker killed the right side of my Beyer DT-990.  Popped my Tung-Sol 5998 and all is good.  I say it could be defective tubes or were very bad handle by the shipping.  Lesson learn, never connect hp when using new tubes. From now on I always disconnect hp when changing tubes, only after 10 mins of warmup i put them in.

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