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Old 9th July 2007, 10:03 AM   #1
Elegant is offline Elegant  Viet Nam
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Join Date: Sep 2006
Default Newbie need to help

Hello every body,

One chanel of 300B tube power amplifier has no sound when I turn on the power. After I use forefinger knocking on top of the tube, the sound to begin the sing, this problem is repetitive for few hours. I think this problem might be due to the socket but when I change to the other chanel the above problem still same as the talk.

Could you please tell me what is problem with my 300B tube and how to solve this problem.

Thank & Regards

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Old 9th July 2007, 09:38 PM   #2
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Location: Great Britain

Be wary of cooking something else. it sounds to me like the tube has had it. Danger is that you might short out something. There ARE only 3 components in a 300b...

In the absence of better advice I recomend you bin it and avoid killing the OPT's especially since you seem to have done a really good job of isolating the tube as the problem?

Can you see the 4 springs at the top of the tube in position? I have a 300b tube with a goosed heater/ cathode, the heater came loose at the mica in transit, (allegedly) I guess it might have worked as you describe since everything was still touching, at the beginning - until I shook it Now it would clearly short the anode to the cathode internally

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Old 10th July 2007, 04:09 AM   #3
Elegant is offline Elegant  Viet Nam
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Thanks Andy,

It is bad new to me, you mean that my 300B tube might be could not use permanently?

Could you please tell me another solution to solve it?

Thanks again

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Old 10th July 2007, 05:14 AM   #4
Colt45 is offline Colt45  Serbia
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shitty solder joint at the pin of the tube, perhaps?
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Old 10th July 2007, 07:02 AM   #5
Elegant is offline Elegant  Viet Nam
diyAudio Member
Join Date: Sep 2006
thanks colt45.
Your ideal is correct.
The solder joint between pin and glass is a little bit loose therefore when I turn the glass gently the 300B tube to be begin warming up.

It is main reason? how to fix this problem? and what kind of adhesive to be used for it?

Many thanks.
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