Hello. Well first off I normally set bias at 120Vac input. The bias always shits around a bit and it depends on your DVM and how often it samples the voltage it's measuring. How much variation are we talking about? Remember you are measuring mV's, not volts. Also, the bias pots can be a bit touchy. I'm used to it...lol. BTW it's 2000 hours on the outputs so if you have exceeded that, it's time for a re-tube.
Biasing Question: ARC VS 115 Hifigeek
Gary -- Hifigeek1: Hi Gary. Hope you're having an enjoyable Memorial Day weekend. Took a little time to check the bias on my ARC VS 115. I have KT-120 tubes. Admittedly, I'm overdue for an all-around re-tube, including 6H30s.
Here's the Q. Bias wasn't all that far off, but since I was checking anyway, I thought I'd true up the bias to 65mV. I found that as I made small adjustments to the biasing pots around the 65mV point, bias would either move a lot or hardly at all. I got to the point that I turned the bias all the way down to minimum and then slowly working my way back. Still took more time zoning in than I thought it should have.
Is this normal? Or does it indicate, that a re-tube would indeed be timely. Or possibly something wrong with the pots or something else? Any thoughts? Thanks
Here's the Q. Bias wasn't all that far off, but since I was checking anyway, I thought I'd true up the bias to 65mV. I found that as I made small adjustments to the biasing pots around the 65mV point, bias would either move a lot or hardly at all. I got to the point that I turned the bias all the way down to minimum and then slowly working my way back. Still took more time zoning in than I thought it should have.
Is this normal? Or does it indicate, that a re-tube would indeed be timely. Or possibly something wrong with the pots or something else? Any thoughts? Thanks
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