QSC ISA 280, Technical & Service Manual

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22 QSC Audio Products, LLC
TD-000163-00 Rev. B
back up until the output clips. The voltage at which the signal
starts to clip should fall within the range shown in Table 1. If
the clipping is asymmetrical, that is, the signal clips on either
the positive or negative side first, adjust R139 to make it
symmetrical.
6. Turn the gain control down. If the amp has begun to warm up
shut it off and let it cool a few minutes before proceeding
with Channel 2.
7. Repeat steps 1 through 5 for Channel 2. Use trimpots R239
and R240 to adjust the current limiting in steps 11 and 12.
8. Turn both channels’ gain controls all the way down. Clamp the
ammeter onto one of the amp’s AC wires and check the amp’s
idle current. If the amplifier is still at about room tempera-
ture, the idle current should match the value shown in
Table 1.