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Post subject: Re: Life is good...
Posted: Tue Jul 29, 2014 8:41 pm
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LB, February of 2001.

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Post subject: Re: Life is good...
Posted: Tue Jul 29, 2014 8:53 pm
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It has real solder! :!:

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Post subject: Re: Life is good...
Posted: Tue Jul 29, 2014 9:36 pm
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shimmilou wrote:
It has real solder! :!:


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:mrgreen:

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Post subject: Re: Life is good...
Posted: Sat Aug 02, 2014 11:33 am
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Now that Chuck's given the thumbs up, I feel 1000% better, :D .

On another note, I was studying the schematics and noticed fender suggest to set the bias at the test point to -37v. Since this does not take into account plate voltage, I'm guessing that this might not be the best way to bias the amp. Has anyone here used that method to bias their DRRI? After biasing the new EH6v6's I installed with a bias probe and reading the plate voltage, I measured this value just for comparison.......-34v.

I'd like to hear members thoughts regarding this.

Thanks

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Post subject: Re: Life is good...
Posted: Sat Aug 02, 2014 1:14 pm
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Your bias supply voltage at TP5 should measure around -49 VDC.

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Post subject: Re: Life is good...
Posted: Sun Aug 03, 2014 4:46 pm
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socal323 wrote:
...I was studying the schematics and noticed fender suggest to set the bias at the test point to -37v. ...


That isn't really a suggestion, that is just where they set it at the factory. The closer to zero, the higher the idle current. Note that at your bias setting, that negative voltage is closer to zero than the factory setting, indicating a higher idle current than the factory. Typically, Fender sets the bias quite cold, and most prefer it hotter.

As you correctly pointed out, you have to account for Plate voltage as well as taste for the particular tubes used.

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Post subject: Re: Life is good...
Posted: Mon Aug 04, 2014 8:55 pm
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Retroverbial wrote:
Your bias supply voltage at TP5 should measure around -49 VDC.

Arjay



Yup, -49 VDC at TP5.

shimmilou wrote:
socal323 wrote:
...I was studying the schematics and noticed fender suggest to set the bias at the test point to -37v. ...


That isn't really a suggestion, that is just where they set it at the factory. The closer to zero, the higher the idle current. Note that at your bias setting, that negative voltage is closer to zero than the factory setting, indicating a higher idle current than the factory. Typically, Fender sets the bias quite cold, and most prefer it hotter.

As you correctly pointed out, you have to account for Plate voltage as well as taste for the particular tubes used.


That's what I was thinking was happening. I biased them on the hot side so that explains why the value went less negative.

Thanks

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Post subject: Re: Life is good...
Posted: Mon Aug 04, 2014 8:59 pm
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socal323 wrote:
I biased them on the hot side so that explains why the value went less negative.


Monitor your output tubes periodically for any evidence of red-plating. If there are no indications after several hours you're prolly "in the pocket" as far as idle-bias goes.

Arjay

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