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Crack;Bottlehead OTL - Page 422

post #6316 of 6326

Have you done all of them, or just the ones near the noisy tube?

post #6317 of 6326
Quote:
Originally Posted by Loquah View Post
 

Have you done all of them, or just the ones near the noisy tube?

All of them

post #6318 of 6326

Wow. That's weird then. I wonder what's causing it!?

 

Sounds like a case to take over to the Bottlehead Forum where the experts who designed it are.

post #6319 of 6326
Quote:
Originally Posted by Loquah View Post
 

Wow. That's weird then. I wonder what's causing it!?

 

Sounds like a case to take over to the Bottlehead Forum where the experts who designed it are.

I already use both forums for it. Never know in which forum some great info jumps out. 

post #6320 of 6326

Very true! Hopefully someone on the BH Forum will have a solution for you

post #6321 of 6326
Sounds like the tube is resonating for some reason, possibly loose construction in the tube. Did you say that you can hear it in the audio? This will sound weird, but I've had luck turning my WA3 on its side and let the tube get good and hot, then rap it with the eraser end of a pencil and sometimes they stop whining. Then turn it off and let it cool sideways. It's a last resort, and some will say crazy, but I've silenced a number of tubes this way.....I've also killed one. The tube might arc when you hit it, so use a pair of cheesy headphones and not your good ones.
Quote:
Originally Posted by Klots View Post

I already use both forums for it. Never know in which forum some great info jumps out. 

Edited by GrindingThud - 12/14/14 at 2:56pm
post #6322 of 6326
Quote:
Originally Posted by GrindingThud View Post

Sounds like the tube is resonating for some reason, possibly loose construction in the tube. Did you say that you can hear it in the audio? This will sound weird, but I've had luck turning my WA3 on its side and let the tube get good and hot, then rap it with the eraser end of a pencil and sometimes they stop whining. Then turn it off and let it cool sideways. It's a last resort, and some will say crazy, but I've silenced a number of tubes this way.....I've also killed one. The tube might arc when you hit it, so use a pair of cheesy headphones and not your good ones.



But if both tubes were quiet before and now both tubes have the same noise, then it can't be the tube?

post #6323 of 6326
How many 5998 make the noise? I thought your 6AS7 was quiet.....
post #6324 of 6326
Quote:
Originally Posted by GrindingThud View Post

How many 5998 make the noise? I thought your 6AS7 was quiet.....



I thought it was quiet too, but yesterday after 1 hour of listening the noise came in. It is lower frequency than with 5998, but it is still there, and it goes quiet when tapped like with the 5998. Previously both tubes were perfectly silent. Less than a month ago that noise appeared for the first time. But if both tubes react the same, then the tube(s) should not be the cause. That squeal does not get louder with volume. I change out electrolytic caps today and see if anything changes. 

post #6325 of 6326
I have piles of bad tubes...they are very old, and many are just not up to the task of high quality audio. You might just have 2 bad tubes. It is also possible something else is wrong....but it used to work, so I suspect the tubes is it.
Quote:
Originally Posted by Klots View Post



I thought it was quiet too, but yesterday after 1 hour of listening the noise came in. It is lower frequency than with 5998, but it is still there, and it goes quiet when tapped like with the 5998. Previously both tubes were perfectly silent. Less than a month ago that noise appeared for the first time. But if both tubes react the same, then the tube(s) should not be the cause. That squeal does not get louder with volume. I change out electrolytic caps today and see if anything changes. 
post #6326 of 6326

^Agree with GT's assessment.  I have had several power tubes do this as well - one of which was actually a very quiet tube until I fumbled it on to my hard wood floor, resulting in the hum and some loose glass in the base.  As far as short term fixes - I've had success wrapping a long thick rubber band around the base of the humming tube and then tipping it slightly in the socket at various angles until the tube runs quiet.  Real tube dampers would probably do the trick as well.   

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