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Scratching sound from tube?

post #1 of 10
Thread Starter 
I have had my mullards EF95 for couple of weeks and listened extensively. Liked the sound and all. However, few days ago one of the tubes started producing scratching noise and it seems to get louder now. Switched the sides and the noise switched too. Volume pot doesnt affect it, its same with volume all the way down. Music is still great and there isnt channel imbalance, but in silent parts its annoying noise. Is this the sign of dead/dying tube?
post #2 of 10
Was it OK when you got it? How many hours are on the tube.

It could be a leak. If the noise switched sides when you switched the tube you know it is a faulty tube.
post #3 of 10
If you wire brush the pins on the tube(s), the problem will likely go away. Sometimes lite oxidation builds up on the pins and will create a noise like you described.

- augustwest
post #4 of 10
You might try an old toothbrush and rubbing alchohol to give 'em a good scrubbing. One of the problems with tube rolling is that sometimes a set of tubes has pins oversized and they widen the tube sockets so skinny pin tubes like Mullards are sometimes a loose fit. Particularly if it's the grid pin that's loose, since it's a very high impedence connection.
post #5 of 10
With the amp umplugged you can use tooth picks to close up the tube sockets to help improve the contact with the tube pin.
post #6 of 10
Thread Starter 
Quote:
Originally Posted by tbonner1 View Post
Was it OK when you got it? How many hours are on the tube.

It could be a leak. If the noise switched sides when you switched the tube you know it is a faulty tube.


Yup, they were perfectly fine when I got them. Dont know how many hours they had though.

I'll try to clean the pins when I get my hands on some alcohol, other than my booze that is.
post #7 of 10
Everyone should own a bottle of Caig ProGold contact cleaner. It's indispensable.
post #8 of 10
Quote:
Originally Posted by MaZa View Post
Yup, they were perfectly fine when I got them. Dont know how many hours they had though.

I'll try to clean the pins first thing,when I get my hands on some alcohol, other than my booze that is.
Stolichnaya will work fine

Skykab's advice about Caig's Pro Gold is as good as advice gets. I clean pins first, new or old and use a small amount of ProGold before I plug 'em in.
post #9 of 10
Thread Starter 
I remembered that I had some cleaning contact-spray (which I had used with my old amplifiers when volume knobs and such started to get scratchy and losing balance), and it worked! No more scratching! Thanks folks.
post #10 of 10
If you still have scratching sound even after you clean your tubes with contac-spray, try to contac-spray clean the tube contact inserts itself on the amp. This trick worked in my tube amp.
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