Please Help with Sound Valves M40 Monoblock Bias Adjustment Procedure!!! - diyAudio
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Old 19th September 2006, 09:37 AM   #1
mq1688 is offline mq1688  United States
diyAudio Member
Join Date: Nov 2005
Location: Santa Clarita, California
Default Please Help with Sound Valves M40 Monoblock Bias Adjustment Procedure!!!

I own a pair of Sound Valves M40 Monoblocks, bought them used a while back. Please help me with bias adjustment procedure. I do not have the operation manual. This is the first re-tubing experience. Your helps are greatly appreciated. Many many thanks! -Mike Q.
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Old 13th February 2013, 05:27 AM   #2
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Join Date: Feb 2013
do you still need help on M40's? if you do i will dig out my manual , i also do have a schematic. you just have to set to 1 Volt , using VOM test point + and ground (one of the chassis screws)
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Old 6th April 2013, 05:14 AM   #3
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Join Date: Apr 2013
I also own a pair of M40 monoblocks. It was in my garage for almost 10 years before I took it out again and powered it up. I readjusted the bias and it'd been working well for some time until the green LED on one of the amps went out. The LED itself is fine, and it would always turn on (after a minute or so from red upon powering up), but after 10 minute or so the green LED would go out. I checked the bias but it seemed to be fine. The amp also sounds fine. Does anyone know what is happening? Is it indication that the tubes are reaching end of life? I seemed to recall that the green LED monitors the cathode current but if the bias is correct it doesn't seem to make sense that the green LED would go out.
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