STEP-BY-STEP OUTPUT TUBE BIASING PROCEDURE
RM200MkI/MkII Tube Biasing instructions (written for 4-Ohm speaker tap use):
1. Adjust your voltmeter to read DC volts, 200 milli-Volt range.
2. Turn on your RM200MkI/MkII amplifier and allow your RM200MkI/MkII to fully warm-up
(approximately 15-minutes).
Please note your RM200MkII has two 70-Amp rated “high in-rush” power switches for long
switch life. One power switch is marked “Master/Forming,” and the other is marked “Play.”
Please press the “Master/Forming” power switch to the “on” position first. Then, press the
“Play” power switch to the “on” position, and allow your RM200MkII to fully warm-up
(approximately 15-minutes).
3. To test one channel, please insert the "red"/"positive" (+) probe into the test point
(marked "TP+") closest to the tube to be tested (say "V6"), and place the "black"/"negative"
(-) probe on the (-) 4-Ohm binding post that is connected to your speaker cable and is
closest to the test point ("TP+")/tube you are testing (say "V6"). Please make sure your
probes are making firm contact...
4. Note the Bias Reading of the tube you are testing (say "V6"). (Bias reading should be
between the “Recommended” mV and “Maximum” mV Bias Values listed in the table
above for your RM200MkI/MkII).
5. Then, test the other tube in that same channel (say "V4"), by inserting the "red"/"positive"
(+) probe into the test point (marked "TP+") closest to the tube to be tested (say "V4"), and
place the "black"/"negative" (-) probe on the (+) 4-Ohm binding post that is connected to
your speaker cable and is closest to the test point/tube you are testing (say "V4)."
6. Note the Bias Reading of the tube you are testing (say "V4"). (Bias reading should be
between “Recommended” mV and “Maximum” mV Bias Values listed in the table
above for your RM200MkI/MkII).
7. Please average the two Bias Readings for one channel, and note the "Averaged Bias
Reading" for that channel.
For example, let's assume the Bias Reading for "V6" reads "38mV," and the Bias Reading
for tube "V4" reads "36mV." Then, the "Averaged Bias Reading" would be "37mV."
8. Use a fine flat-head adjustment screwdriver (we recommend a 2.5mm by 55mm
screwdriver) to adjust the Bias of your RM200MkI/MkII so each tube is set to your desired
Bias setting/reading.
For example, let's assume you wish to set the "Average Bias" of your RM200MkI/MkII at
"35mV." And, let's assume the Bias Reading for "V6" reads "38mV," the Bias Reading for
"V4" reads "36mV," and therefore, the "Average Bias Reading" for the right channel is
"37mV."
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