• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

what should my mulit reader be on to bias yaqin 100b

Hi Youngie. Set your meter to 2000m on the V scale, that is second click clockwise from OFF.
Place the meter Black lead between Meter socket COM to the desired monitor point -
Place the meter Red lead between Meter socket VΩmA to monitor point +.

You need to adjust the bias control associated with the monitor sockets you are measuring, to a figure of 550mV (the meter may show 0.550).

BE AWARE - the adjustment controls work in reverse to what you may expect - you have to turn the controls CLOCKWISE to reduce the measured voltages.
Take care - it is easy for the newcomer to accidentally exceed the maximum figure, a lot of 100B owners in fact prefer to run their amps with the bias set to 0.45 to 0.50 i.e. 450mV to 500mV.


2012-01-14 2:54 pm
thank you so much mate. i have set them all at 0.55 but when i go into tr mode i can only get a reading from 3 not 4 the v4 will not read in tr mode. is there any reason for this. one more thing i have a pre amp xiang sheng 728a. witch i want to use on my yaqin 100b. what is the best way to set them both up together for a better sound around cheers lee
I cannot see how you lose all valve current just by switching into Triode mode, even if the switch was defective I would expect something to be shown on your multimeter. However, you obviously have a problem with the switching which is as attached. If the amplifier is new, it may be worth contacting the seller. I have no experience of using a pre-amp as I find the output of all my ancillary equipments are adequate to drive the amplifier direct.


  • 100b patch.JPG
    100b patch.JPG
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