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
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
We would have to see a circuit to have some idea of possible problems but given that the description describes three EL34's essentially in parallel per channel points to a problem around one of them. If you've swapped them around then its obviously not the individual valve.
It may be anything from a problem with the switches used for monitoring (meaning no real fault within the amp) to a problem with the biasing or supply to that one valve.
Without a circuit its impossible to say. You would need to do basic checks of looking at current flow in each valve and to tell you how to do that needs a circuit diagram. Typically you might measure the voltage across each cathode resistor for example.#
A generic type circuit here:
http://www.audiodesignguide.com/my/el34_pse/2A3pse_sch1a.JPG
Voltage across the 47 ohm's in this circuit would tell you a lot about where the issue was.
It may be anything from a problem with the switches used for monitoring (meaning no real fault within the amp) to a problem with the biasing or supply to that one valve.
Without a circuit its impossible to say. You would need to do basic checks of looking at current flow in each valve and to tell you how to do that needs a circuit diagram. Typically you might measure the voltage across each cathode resistor for example.#
A generic type circuit here:
http://www.audiodesignguide.com/my/el34_pse/2A3pse_sch1a.JPG
Voltage across the 47 ohm's in this circuit would tell you a lot about where the issue was.
