Boulder Amplifiers 860 - Manual (Page 13)

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SHORTED OUTPUT DETECTION
If the output of the amplifier becomes shorted, the front panel
indicator will turn red and the amplifier will turn off the output stage
for about three seconds, then very briefly try to turn on again. If the short
still exists, this cycle will repeat until the short circuit is removed.
THERMAL PROTECTION
A thermal protection circuit prevents high case temperatures which
are unpleasant to the touch and potentially harmful to the amplifier. The
thermal cutout circuit will mute the amplifier when the transistor cases
reach 85°C, and the indicator will turn red.
If this happens, more ventilation should be provided for the
amplifiers.
MAINTENANCE
No routine maintenance is required for the Boulder 860 Stereo Power
Amplifier. However, to keep operating temperatures at a minimum, do
not block the heat sinks, and remove any dust buildup that may occur.
OPERATION