Indicators - Crown MA-1202 Operation Manual

MA Series Power Amplifiers
4 Operation
Operation Manual

4.4 Indicators

The amber Enable indicator is provided to
show that the amplifier has been turned on (or
enabled), and that its low-voltage power supply
and forced-air cooling system are working. It
does not indicate the status of the high-voltage
power supplies. For example, the Enable indi-
cator will remain lit during unusual conditions
that would cause the amplifier's protection sys-
tems to put a high-voltage power supply in
"standby" mode (see Section 5.1.2).
The amber ODEP indicators confirm the nor-
mal operation of Crown's patented Output
Device Emulation Protection circuitry. During
normal operation, they glow brightly to show
the presence of reserve thermal-dynamic
energy. They dim proportionally as the energy
reserve decreases. In the rare event that there is
no reserve, the indicators turn off and ODEP
proportionally limits the drive level of the out-
put stages so the amplifier can continue safe
operation even when conditions are severe.
(For a more detailed description of ODEP, see
Section 5.1.1.)
Figure 4.3 Indicators
The ODEP indicator for the affected channel will
turn off if a high-voltage power supply is put in
"standby" mode, a high-voltage power supply
fuse (or breaker) blows, or a transformer acti-
vates its thermal protection circuitry (see Sec-
tion 5.1.3). Both ODEP indicators turn off if the
amplifier loses AC power, the power switch is
turned off or the low-voltage power supply fuse
blows.
The green Signal/IOC indicators show sig-
nal presence and distortion. As signal presence
indicators, they flash with normal intensity in
sync with the output audio signals. As IOC
(Input/Output Comparator) indicators, they
flash brightly if there is any difference between
the input and output signal waveforms greater
than 0.05%. Because transient distortion hap-
pens quickly, a 0.1 second "hold delay" keeps
the indicators on long enough to be easily
noticed. The IOC function essentially provides
proof of distortion-free performance. Note: The
Channel 2 IOC indicator will remain lit when
running in Parallel-Mono mode.
Under conditions where one of the amplifier's
high-voltage power supplies is temporarily put
in standby mode, the Signal/IOC indicators will
stay on with full brightness. They will resume
normal operation when the amplifier is no
longer in standby mode.
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