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 Post subject: Rebel 20 biasing
PostPosted: Wed, Apr 21, 2010 12:26pm 
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Supah Stah
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I have several RM MTS amps so I understand how those work but, I just picked up a Rebel 20 last night. I was wondering if I open it up, is checking the bias just as easy on these? Are the contact points labeled and all that?


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 Post subject: Re: Rebel 20 biasing
PostPosted: Wed, Apr 21, 2010 12:35pm 
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Hack

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The bias test points are marked and the recommended bias voltage is printed on the PCB legend.

Image


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 Post subject: Re: Rebel 20 biasing
PostPosted: Wed, Apr 21, 2010 1:07pm 
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Supah Stah
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That was a better answer than I expected! Thank you.


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 Post subject: Re: Rebel 20 biasing
PostPosted: Wed, Apr 21, 2010 3:39pm 
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Hack

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Where do you plug the black lead from the volt meter?


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 Post subject: Re: Rebel 20 biasing
PostPosted: Wed, Apr 21, 2010 4:01pm 
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Rock God
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WIRED wrote:
Where do you plug the black lead from the volt meter?

You could just stick the black lead into the screw hole on the chassis,it's just a ground.

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 Post subject: Re: Rebel 20 biasing
PostPosted: Wed, Apr 21, 2010 11:14pm 
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Really dumb question but I'm asking anyway...when you're biasing a Rebel 20 or 30, you do it with the power on, speaker(s) plugged in, guitar plugged in right? Or can you bias it while on standby? Or while it's off?


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 Post subject: Re: Rebel 20 biasing
PostPosted: Thu, Apr 22, 2010 5:38pm 
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Turn it on, no guitar. Not on standby, let it warm up and take your readings and adjust with the trimpot if necessary. Be careful, there are lethal voltages in there. If you're not sure, let a tech do it.


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 Post subject: Re: Rebel 20 biasing
PostPosted: Fri, Apr 23, 2010 5:02pm 
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First of all mad props & thanks to Danelectro & bbrodiefor the graphic and tips. That being said, the picture has the test points backwards. The 6V6 testpoint is actually the one that Danelectro has labeled "EL84", however it's kind of hard to screw up anyways because Bruce in his mighty wisdom has them labeled on the PCB as well as the correct voltages to bias to.
Now that I've got all that out of the way, I must say that biasing my Rebel 20 was a cakewalk. Went to the shack and picked up a digital multimeter for 20 bucks. Owned my Rebel 20 for about a year. Haven't swapped any tubes, still has stock JJ's in the power and soveteks in pre. Interestingly, when I checked the bias, BOTH the 84's and the 6V6's were a tad on the cool side...about about 36mv on the 84's and about 40 on the 6V6's. Makes me wonder if power tubes have a bit of a break-in period. Made the adjustment in a matter of moments and a great amp sounds even a little better. Thanks for this thread and all the help. Egnater rules!


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 Post subject: Re: Rebel 20 biasing
PostPosted: Fri, Apr 23, 2010 10:15pm 
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Immortal Rock God
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Break in period and they drift as time goes on.

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