USER GUIDE
CTM-200-RACK
2/ "BIAS" - In this mode the meter will glow RED.
To check the bias of the output tubes proceed as follows:
Run the amplifier for at least 10 mins to allow the output tubes to fully heat up with
the amplifier set to mute. Standby on. Select.. Tube 1 and with an insulated jewelers
screwdriver gently adjust the trimmer situated on the rear panel. The reading to aim
for is the needle just at the start of the red ie 0db.
Note that although each tube can be adjusted individually it is possible to get tubes
that cannot be adjusted to the correct reading, these can still be used providing the
reading is not in the red, a lower reading is acceptable and will note impact audibly
on the power output or sound quality of the amplifier.
Please also note that the trimmers are 25 turn types to make adjustment easy, This
type of adjuster has no end stop so if you reach a point where the adjuster will
not give any more adjustment then the output tube will have to be replaced if the
reading is to high ie in the RED.
Repeat this for each of the four output tubes in turn.
RETURN THE METER TO "audio" MODE AFTER BIASING. DO NOT RUN THE
AMPLIFIER IN BIAS MODE WHILST PLAYING.
Note there is a protection fuse fitted to each of the output tubes and if no reading
is obtained on the meter this fuse will have failed. The protection fuses are situated
next to the output they are protecting the correct rating is 315Ma quick blow, in the
event of a blown fuse they MUST be replaced with fuses of the correct rating and
type.
A continually blowing fuse would indicate either an incorrectly biased output tube
or a defective output tube.