Setting The Bias - Velleman K8060 Assembly Manual

Test & adjustments
•
Turn the RV1 bias adjust trimmer fully counter clockwise (turn left) before applying power for the first time.
ADVICE: For safe first-time testing insert a 60W light bulb in series with the AC power and the trans-
former. If the light bulb lights up continuously, disconnect the transformer and check all your wiring and
assembly. Reconnect the power supply. If the lamp remains off, everything is OK, replace the light bulb
with a fuse.
If the TR8040 transformer is used there is a selection of primary AC voltage :
120Vac: black / brown.
230Vac: black/orange.
IMPORTANT: Insulate the wire that is not being used.
NOTE: Two amplifiers and two transformers are required for stereo. Never attempt to run two amplifi-
ers from a single transformer!

Setting the bias:

•
Connect a multimeter (lowest DC voltage range 1V or lower) over the leads of R19 (polarity is indicated on
the PCB).
•
Turn on the power, the power LED should light.
•
Check the multimeter, it should read 0V, adjust RV1 carefully to about 10mV (0.01V) Wait a few minutes
until the meter reading remains stable.
•
Turn off the AC power. The amplifier is now ready for use.
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