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Post subject: Chopstick on tubes ; beware
Posted: Mon Oct 28, 2013 4:25 am
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I read that on Tube store ;

www.thetubestore.com/Resources/Product- ... ube-Review

_________________________________________

NOTE: For those of you that love to take a pencil and whack hot tubes, you will be rewarded with a satisfying, loud, "PING". It's the nature of the beast with any large plate dual triode used in V1. If you get uncontrolled squealing at higher volume levels or if touching the amp causes a ringing noise you probably have a genuine microphonics problem. If you like to tap your tubes all the time to see if they are microphonic, you will likely cause a genuine microphonics problem.
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Post subject: Re: Chopstick on tubes ; beware
Posted: Mon Oct 28, 2013 4:25 pm
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stratele52 wrote:
If you like to tap your tubes all the time to see if they are microphonic, you will likely cause a genuine microphonics problem.


+1

Absent the normal symptoms of a microphonic bottle, this test should only be performed "as needed" -- ie: when spurious-and-suspicious noise(s) are manifest. And the impact force when conducting this test should only be sufficient to simulate the nominal vibrations which would be present when playing the amp under operational conditions.

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Post subject: Re: Chopstick on tubes ; beware
Posted: Mon Oct 28, 2013 4:32 pm
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Retroverbial wrote:
stratele52 wrote:
If you like to tap your tubes all the time to see if they are microphonic, you will likely cause a genuine microphonics problem.


+1

Absent the normal symptoms of a microphonic bottle, this test should only be performed "as needed" -- ie: when spurious-and-suspicious noise(s) are manifest. And the impact force when conducting this test should only be sufficient to simulate the nominal vibrations which would be present when playing the amp under operational conditions.

Arjay


Just did this the other day with the first 12AX7 I put in V1 of my BDRI. it sounded odd with some strange background noise. A few very light taps with a chop stick showed it to be very noisy with a bright "tink tink" sound. The next tube made more of a "thunk thunk" sound with no noises when played.

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Post subject: Re: Chopstick on tubes ; beware
Posted: Mon Oct 28, 2013 5:12 pm
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For input stage, I tap the chassis next to V1. If V1 is microphonic, you will hear it, for sure.


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Post subject: Re: Chopstick on tubes ; beware
Posted: Mon Oct 28, 2013 10:54 pm
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Not a subscriber to the chopstick method, for tubes. A pencil eraser or finger is more than aggressive enough. And that seems to be rarely necessary. Microphonic symptoms will become apparent under operating conditions. Some tubes are the best sounding, for playing purposes. But won't stand up to the"tap test". If they ring on certain notes, then OK, they're done. Tubes are microphonic by their very nature!! Some of my Telefunkens will exhibit a protest, when tapped with a finger nail. But, their function in the amp is excellent. JMO, Art

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Post subject: Re: Chopstick on tubes ; beware
Posted: Mon Oct 28, 2013 11:49 pm
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Yeah, you need to be careful. But, a slightly noisy tube will become microphonic. I do this test with amps for others. To place the quietest tubes, esp critical positions (V1, reverb driver and PI). So, that the owner's amps go noisy too quickly (like within a year).


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Post subject: Re: Chopstick on tubes ; beware
Posted: Mon Oct 28, 2013 11:58 pm
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You can use a chopstick, a popsicle stick, a wooden pencil, even a plastic swizzle stick from McDonald's. Personally, I use a dielectric tuning tool left over from my radar-maintenance days. The operative protocol is, be gentle.

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Post subject: Re: Chopstick on tubes ; beware
Posted: Mon Oct 28, 2013 11:59 pm
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For sure, Steve, it's a trade-off!!! Your point is well taken!!! Art

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Post subject: Re: Chopstick on tubes ; beware
Posted: Tue Oct 29, 2013 12:49 am
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Retroverbial wrote:
You can use a chopstick, a popsicle stick, a wooden pencil, even a plastic swizzle stick from McDonald's. Personally, I use a dielectric tuning tool left over from my radar-maintenance days. The operative protocol is, be gentle.

Arjay


Agree. Everyone is writing like people are wailing away on their tubes with a 5 pound sledge. I barely tap the tube with the chop stick. I think the vibrations caused by my BDRI at full tilt are more than when I tapped V1 with a chopstick. I really don't see what the big deal is.

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Post subject: Re: Chopstick on tubes ; beware
Posted: Tue Oct 29, 2013 1:10 am
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bluesky636 wrote:
I really don't see what the big deal is.


+1

My Dad taught me about microphonic tubes while helping me assemble my first "All-American 5" superhet AM radio when I was around 11. He subbed a wonky bottle into the audio stage and showed me how to isolate and identify it. Just another facet of troubleshooting a tube audio circuit.

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Post subject: Re: Chopstick on tubes ; beware
Posted: Tue Oct 29, 2013 5:54 am
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It's unwise to advise anyone to "tap" tubes for any reason, they are fragile. Yes, one mans tap is another mans whack. All tubes are microphonic, that's exactly how they work, it's normal. You're in sad shape if you have to rely on a stick to troubleshoot a tube amp. :wink:

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Post subject: Re: Chopstick on tubes ; beware
Posted: Tue Oct 29, 2013 6:11 am
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shimmilou wrote:
It's unwise to advise anyone to "tap" tubes for any reason, they are fragile. Yes, one mans tap is another mans whack. All tubes are microphonic, that's exactly how they work, it's normal. You're in sad shape if you have to rely on a stick to troubleshoot a tube amp. :wink:



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Post subject: Re: Chopstick on tubes ; beware
Posted: Tue Oct 29, 2013 6:43 am
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shimmilou wrote:
It's unwise to advise anyone to "tap" tubes for any reason, they are fragile. Yes, one mans tap is another mans whack. All tubes are microphonic, that's exactly how they work, it's normal. You're in sad shape if you have to rely on a stick to troubleshoot a tube amp. :wink:


Guess we'll have to agree to disagree.

How do you suggest someone look for a bad solder joint?

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Post subject: Re: Chopstick on tubes ; beware
Posted: Tue Oct 29, 2013 7:17 am
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bluesky636 wrote:
[

How do you suggest someone look for a bad solder joint?


Do some test , locate wich section do not work propely and reheat solder could be defective if no components is defective. With experience you can see if solder mays be bad .

This is not for you Bill : If no electronic skill or knowledge to trouble shouting an amp you can try your best with any tool you have .


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Post subject: Re: Chopstick on tubes ; beware
Posted: Tue Oct 29, 2013 9:52 am
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stratele52 wrote:
bluesky636 wrote:
[

How do you suggest someone look for a bad solder joint?


Do some test , locate wich section do not work propely and reheat solder could be defective if no components is defective. With experience you can see if solder mays be bad .


Which is typically done by tapping on a joint or gently pushing on a component, and listening for noise, crackles, etc. I don't agree that you can easily tell a bad solder joint by sight alone.

These methods have all been discussed and advocated here and in other forums. The key word is "gently". Anyone banging on anything has no business with thier hands inside an amp, however, a good tech should know what works and what doesn't and how to use the tools at hand. Given how amps are handled on stage, transported in vehicles, and shipped across country, I think the occasional gentle tap with some item is the least of anybody's worries. Yeah, tubes are fragile, but they are not that fragile. Otherwise, how would a tube survive more than a few minutes in a Twin Reverb? :lol: :lol: :lol:

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