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EQUIPMENT FORUMS >> TORII JR >> Normal to need bias adjustment after 3 months?
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Message started by AlexR on 06/02/20 at 23:50:08

Title: Normal to need bias adjustment after 3 months?
Post by AlexR on 06/02/20 at 23:50:08

Still getting to know my new (to me) Torii Jr. Today I decided to check the bias and it was 435 millivolts. Is it normal for the Torii Jr to drift this much with 3 months of use?

Also, when I adjust bias using the multimeter, the reading doesn't stay fixed, but fluctuates rapidly by about 3 digits +/- 825 millivolts. Is this normal?

The entire tube compliment in the amp was new from Decware as of early March.

Thanks for the help!

Title: Re: Normal to need bias adjustment after 3 months?
Post by Chester on 06/03/20 at 05:22:25

Hi Alex,

I would say that is not normal at all. Please don’t take this the wrong way, but are you sure you are using the multimeter correctly?

The voltage will fluctuate, but in my experience not by more than one or two millivolts. So, on my meter, 826 or so.

If you are 100% on the multimeter use, then I’d call Steve.

Good luck.

Title: Re: Normal to need bias adjustment after 3 months?
Post by AlexR on 06/03/20 at 22:34:56

Chester, thanks for your thoughts. I'm not the most technically minded, but I believe I'm using the multimeter correctly. That said, it's entirely possible I'm flubbing it. Here are some pics of my process, please feel free to let me know if something doesn't look correct.

Thanks again for your help.

Title: Re: Normal to need bias adjustment after 3 months?
Post by Archie on 06/03/20 at 23:46:51

I just had a thought about the fluctuations. First, the difference between 1 or 2 mV and 3 doesn't seem like a big difference. Second, I wonder if the fluctuation either has to do with equipment warmup or line voltage fluctuation. As for the former, I get a variation on my ZMA meters that can take hours to fully settle after a cold start.

Title: Re: Normal to need bias adjustment after 3 months?
Post by HockessinKid on 06/04/20 at 00:40:51

Wow, hours for the ZMA bias meters to settle in?? Mine are usually up in no more than 10 minutes and stay rock solid. This with the TAD 7027a tubes, TungSol 7027a - 7581 - KT66 tubes, and Gold Lion KT66's. Never experienced any problems.

HK

Title: Re: Normal to need bias adjustment after 3 months?
Post by Archie on 06/04/20 at 01:18:19

I'm talking about parts of a mA. It does depend on the tube and the age of the tube. If your meters are exactly the same from 10 minutes to shutdown, that's awesome.