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 Post subject: Flash of light
PostPosted: Mon Sep 11, 2017 9:48 am 
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Mark III
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When I turned on my amp the other day, from standby to on, I heard a loud "pop" through the speakers and saw a bright flash of light in one of the power tubes. I turned it back to stand by, inspected and then back to on. No noise and no flash of light. I've turned it on and off several times since with no issue. It's performing as well as ever.

Now I know, that a flash of light within power tubes can be a signal of near future failure. The tubes in there now are about 7 years old.

Should i just replace or let them go a while longer and just monitor?

Thanks

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 Post subject: Re: Flash of light
PostPosted: Tue Nov 28, 2017 7:17 am 
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swbo101 wrote:
When I turned on my amp the other day, from standby to on, I heard a loud "pop" through the speakers and saw a bright flash of light in one of the power tubes. I turned it back to stand by, inspected and then back to on. No noise and no flash of light. I've turned it on and off several times since with no issue. It's performing as well as ever.

Now I know, that a flash of light within power tubes can be a signal of near future failure. The tubes in there now are about 7 years old.

Should i just replace or let them go a while longer and just monitor?

Thanks

I would replace them ASAP, powertubes that fail in circuit can take out other components in the amp. You should also have the screen grid resistors checked. A sudden powertube failure can also blow the screen grid resistor on that socket. When the screen grid resistor fails, it 'shuts off' that tube, which may give the illusion that all is OK when actually you are only running on 3/4 of your output tubes.

Good luck, I hope it is just a failed powertube.

Dom

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 Post subject: Re: Flash of light
PostPosted: Tue Nov 28, 2017 3:51 pm 
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Mark III
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Thanks for the reply. Since I originally posted the topic, I've replaced those tubes (hate throwing out tubes :evil: ), but better safe than sorry. I've had them for 7 years so I guess they fulfilled their duty. I haven't brought it to a tech yet, been keeping an eye out & an ear. Volume and tone have been normal, so I'm guessing I pulled them out in time.

Appreciate the response.

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