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Post subject: locating the bias points in a scxd
Posted: Tue Jul 21, 2009 6:46 pm
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I'm hoping some of you guys can help me. I'm planning on changing the 6v6 tubes in my scxd but I can't find the bias points to adjust the bias voltage. This is this the first time I'm doing this so I don't want to screw it up. Can anyone give me a few pointers? Oh, and do you also know the bias voltage as well? Thanks


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Posted: Tue Jul 21, 2009 8:26 pm
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There is lethal voltage in there. If you don't know what you're doing, I'd leave it to a tech. Are you unhappy with the sound? Your amp may not even be biased cold. Different tube manufacturers have different specs. For example, JJ's 6l6's can be run at 80mv and even higher. If you ran GT's that hot they'd probably red plate.

Here is a link http://www.agileguitarforum.com/viewthr ... 815&page=1


The thing is, if you do not know the plate voltage, the mv numbers mean nothing. People throw out mv numbers all the time.
If the tubes run too hot, they usually sound better but won't last as long, too cold and they,ll last forever but sound cold and sterile.

Check out www.eurotubes.com for biasing instructional videos.

Be Careful


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Posted: Wed Jul 22, 2009 5:50 am
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63supro wrote:
There is lethal voltage in there. If you don't know what you're doing, I'd leave it to a tech. Are you unhappy with the sound? Your amp may not even be biased cold. Different tube manufacturers have different specs. For example, JJ's 6l6's can be run at 80mv and even higher. If you ran GT's that hot they'd probably red plate.

Here is a link http://www.agileguitarforum.com/viewthr ... 815&page=1

Oh, and 1mv difference will not make any difference in your tone.
This guy just proves my point.


The thing is, if you do not know the plate voltage, the mv numbers mean nothing. People throw out mv numbers all the time.
If the tubes run too hot, they usually sound better but won't last as long, too cold and they,ll last forever but sound cold and sterile.

Check out www.eurotubes.com for biasing instructional videos.

Be Careful


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Posted: Wed Jul 22, 2009 8:59 am
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I do not believe that the SuperChamp XD has bias pots. I think you just need to retube with a matched set.

But I am not near the amp nor the owners manual at the moment...
Bill M's pages probably address it.

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Ignorance IS bliss - and I am the happiest person here!


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Posted: Wed Jul 22, 2009 10:20 am
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I probably leave something like this to a tech. I was planning on swapping out the stock groove tubes with a set of ruby tubes. I'm also planning to swap out the fender 12ax7 with a tunsol. I guess I am trying to get more of a bite out of this amp. Make it a little more aggressive.


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Posted: Wed Jul 22, 2009 5:29 pm
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Bias pot is R6. Adjust to 40 millivolts at test point 22. Warning! High voltage near test point 22. (around 375 volts, no respect = death) Bias itself is a negative voltage under 50.


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