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Post subject: Fender Hot Rod Deluxe III blowing power tubes - please help!
Posted: Fri Jul 13, 2012 8:13 pm
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Hey folks,

Glad to be part of the forum... I play a Fender USA Jazz V and a Fender USA P-Bass V... looking forward to chatting with folks about them.

Today though, I need some advice about a guitar amp. I'm recording an album for a Halifax NS based indie rock/punk band. The girl playing guitar has a Hot Rod Deluxe III that's acting up. When she brought it in, the 6L6's were glowing blue. The amp sounded great and she had been using it for a while so I figured we could give it a shot. About 10 minutes in she lost 90% of her volume. I swapped out the tubes with another set from an older amp and within minutes one of them was glowing blue and the volume drop occurred again. Today I put another older set in that I know worked well and within 5 minutes or so, same deal... one blue and no volume.

Any idea what I should look at next?

Thanks


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Post subject: Re: Fender Hot Rod Deluxe III blowing power tubes - please h
Posted: Fri Jul 13, 2012 8:15 pm
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I should also mention that if I let the amp cool... I get about 5 minutes again and then the tube goes blue and the drop occurs. Any help would be greatly appreciated.


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Post subject: Re: Fender Hot Rod Deluxe III blowing power tubes - please h
Posted: Fri Jul 13, 2012 10:26 pm
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Probably one of the power valve losts the filament supply. Check all solder joints especially in power section and valve sockets.

:)
;)

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Post subject: Re: Fender Hot Rod Deluxe III blowing power tubes - please h
Posted: Fri Jul 13, 2012 10:43 pm
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Tis-san wrote:
Probably one of the power valve losts the filament supply. Check all solder joints especially in power section and valve sockets.


+1

It could also be a bias-supply problem.

The amp needs to see a qualified tech. Immediately.

Arjay

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Post subject: Re: Fender Hot Rod Deluxe III blowing power tubes - please h
Posted: Sat Jul 14, 2012 2:58 am
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" I swapped out the tubes with another set from an older amp and within minutes one of them was glowing blue and the volume drop occurred again. Today I put another older set in that I know worked well and within 5 minutes or so, same deal... one blue and no volume. "

Lazy, hazy blue glow from an output tube usually is ok. But, if volume drop is associated with the color (that is, volume is ok--- when no blue glow), then it could mean excess current draw. And after 5 minutes of playing it could = parasitic oscillation or other induced instability.

First off, check your idle bias draw. All ok, at the start? See if you are getting excess draw during that "blue glow." If so, you'll need a scope to hunt down the issue. It may not be in the output section, but due to defect in the negative feedback circuit that feeds back to the gain stage.

Translation: you may need a good amp tech.

Good luck! Keep us posted.


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