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Post subject: Re: DRRI: Rectifiers and Bias and well ... I need advice
Posted: Wed Feb 10, 2016 10:54 am
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Apologies if I am going off-topic but I am planning to replace the JJ GZ34 in my DRRI with a Tung-Sol 5AR4 so same type of rectifier.

I have a simple bias probe (that I have never used) so could I check the mA with the JJ rectifier then again with the new Tung-Sol rectifier and if the mA is the same assume no adjustment is necessary?


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Post subject: Re: DRRI: Rectifiers and Bias and well ... I need advice
Posted: Wed Feb 10, 2016 11:23 am
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fifty4 wrote:
I have a simple bias probe (that I have never used) so could I check the mA with the JJ rectifier then again with the new Tung-Sol rectifier and if the mA is the same assume no adjustment is necessary?


Correct, assuming that the existing bias current is within the operating parameters of the output tubes. Adjust as necessary after the rectifier swap.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: DRRI: Rectifiers and Bias and well ... I need advice
Posted: Thu Feb 11, 2016 5:08 am
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Retroverbial wrote:
fifty4 wrote:
I have a simple bias probe (that I have never used) so could I check the mA with the JJ rectifier then again with the new Tung-Sol rectifier and if the mA is the same assume no adjustment is necessary?


Correct, assuming that the existing bias current is within the operating parameters of the output tubes. Adjust as necessary after the rectifier swap.

Arjay

To conclude, the JJ GZ34 gave a bias reading of 21.7 mA and the new Tung-Sol 5AR4 was 21.8 mA so no adjustment made.


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Post subject: Re: DRRI: Rectifiers and Bias and well ... I need advice
Posted: Thu Feb 11, 2016 10:54 am
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I wouldn't pay that miniscule difference any mind.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: DRRI: Rectifiers and Bias and well ... I need advice
Posted: Tue Feb 16, 2016 4:28 pm
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If you're going with a 5Y3, I'd stay away from the Sovtek. They appear to be 5AR4s that didn't make the grade and will not give the same voltage drop as a proper 5Y3. Swapping an NOS or a JJ 5Y3 for the Sovtek "5Y3" lowered my plate voltage 30 volts.


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