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Bias Potentiometer Issue

24.157.130.199

Wondering if anyone in this forum can offer guidance on a minor issue with my Unison Research S6 tube integrated amplifier. This amp has six buttons to adjust the bias - one for each EL34 power tube. There is one "bias meter" per channel and each meter has three buttons associated with it - one for each EL34 tube (six in total).

The issue is that the meter does not react when pressing the top left bias adjuster button. There are no issues with the other buttons. I have tried switching the afftected tube with a different functional EL34 tube but I'm still not getting a meter response - ie - meter needle does not react.

I may be wrong but in my newbie opinion, the tube and its power output do not seem to be affected. The tube glows as usual and there is no audible difference.

Anyone have any ideas of what can be wrong? Anyone believe this is serious enough for me to stop turning on the amp until it's fixed?

Thanks in advance for any response and guidance.
Tony
Tony
Montreal

Follow Ups:

probably just an issue with the button switch - Chip647 13:52:54 01/23/23 (2)
The button just puts the meter on that tube. If the button is not making contact it will not select the tube to display on the meter. Unless you have been fiddling with the tubes potentiometer it should be OK. Probably want to get the button fixed.

Per the manual

BIAS SETUP
The bias of the valve output stage is a mixture a �
automatic, 1/2 manual. The manual setup is done individually
on each output valves.

Pressing the left hand button marked V2 L or R the instrument
at left or right side will move the needle up the scale. At the
same time turn the potentiometer V2 L or R to place the needle
of the instrument exactly in the center between the green and
red zones of the scale.
This operation must be repeated with V3 L or R, V4 L or R .8

Finally we suggest repeating the setup procedure, as the output
stage is a parallel single ended there is a small interaction
between the output valves.
- RE: probably just an issue with the button switch - tonysco 16:41:35 01/23/23 (1)
  Thank you Chip for responding.
  
  So, I need not worry about using it until I get it fixed? Right?
  Tony
  Montreal
  - You are probably very safe (nt) - Chip647 06:17:50 01/25/23 (0)

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