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Old 30th September 2010, 08:40 PM   #1
yan6 is offline yan6  Canada
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Default One channel has less glow

Hi there, I have a yaqin MC-10l. I just changed tubes to some used ones a friend gave me. After re-setting the bias on both channels the same; I noticed one side has much less glow on the two tubes. I'm not sure yet if the audio is stronger in the one channel, if it is its not that noticeable. Any thoughts, is this common?
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Old 30th September 2010, 08:45 PM   #2
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Quote:
Originally Posted by yan6 View Post
Hi there, I have a yaqin MC-10l. I just changed tubes to some used ones a friend gave me. After re-setting the bias on both channels the same; I noticed one side has much less glow on the two tubes. I'm not sure yet if the audio is stronger in the one channel, if it is its not that noticeable. Any thoughts, is this common?
I assume you mean heater glow? This is common. I have a couple of projects that use multiple 807s, 6AQ5s, 6BQ7s, 6BQ6s. Some of these have heaters that are a definite red, yet others a brighter, almost red-orange glow. So long as the heater voltage and current are within spec, and they bias up properly, then the only difference is aesthetic.
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Old 30th September 2010, 09:21 PM   #3
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We have to admit that there is nothing more awesome than some glowing tubes...
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Old 30th September 2010, 09:59 PM   #4
Hi_Q is offline Hi_Q  England
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Snap! Same Amp, Same problem. I think it is due to heater drop as all my latest 6CL6 were uniformly bright but after a time some glowed less than others. I noticed that the heater had physically dropped down inside the cathode on the dimmer ones, the cathode providing more shielding from the heaters glow. I checked the heater volts on all four and all are correct.
Les
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Old 30th September 2010, 10:30 PM   #5
yan6 is offline yan6  Canada
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Ok, that's good to hear. Hi-Q could you tell me how I can check my heater voltage to ensure that it is alright
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Old 1st October 2010, 03:28 PM   #6
Hi_Q is offline Hi_Q  England
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You will need a multimeter, preferably a digital one, set to measure AC Volts.
Connect it as per the attached photo, you can do it on any tube holder though I have a special extender box so I can measure the heater voltage with the tube plugged in. BE CAREFUL ! ! You will see that 450Volts lurk on other pins!
Avoid
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