Lab.gruppen PLM 20000Q - Manual (Page 29)

Operation and Performance
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PLM Series Operation Manual rev 1.2.3
5.3.8.3 Power Supply / DSP
A power supply (PSU) or DSP temperature warning or fault is indicated by the LED in the top-left function
button.
▸ A warning is indicated by a static yellow LED and adjacent warning message: TEMP WARN:PSU
(or TEMP WARN:DSP)
▸ A fault is indicated with a static red LED and adjacent warning message: TEMP FLT:PSU
(or TEMP FLT:DSP)
An event report is sent to the Lake Controller software for both the warning and the fault. If a temperature
fault condition arises in the power supply the output of all channels will be muted. If a temperature fault
condition arises in DSP area, audio will not be muted but continued operation is not recommended.
5.3.8.4 PLM 20000Q
For the PLM 20000Q a temperature dependant limiting feature is also present. At temperatures above the
critical warning level and below the dangerous fault level, the ISVPL threshold is slowly reduced to decrease
the output power and cool down the device. This enables the device to continue to pass audio, although
with a reduced amplitude, in extreme conditions. If reducing the ISVPL threshold does not cool down the
device a temp fault will still be issued when the dangerous temperature level is reached.
5.3.9 DC Protection
DC protection is implemented on each power output to prevent damage to connected loudspeakers or any
PLM components. DC present at the output will cause the PLM’s power output module breaker to blow. In
this instance a red LED will illuminate and NEEDS SERVICE will display on the LCD.
The power output channel modules are independent of
the input voltage. Both 115 and 230 V models have amp
channel fuses. This is not a user-servicable fault
condition and the unit should be returned for repair.
5.3.10 VHF Protection
The PLM includes protection circuits that detect Very High Frequency (VHF) content in the input signal. The
detection is frequency-dependent, initiated from 10 kHz upwards. If VHF signals are detected above the
threshold, the output will mute for approximately 6 seconds before a further measurement is taken. When
continuous VHF signal stops, the output unmutes and the amplifier returns to normal operation.
This protection system recognizes that continuous VHF signals at high levels do not appear in speech or
music. Any such content can therefore be considered as a fault condition. VHF protection is essential to
avoid damage to HF drivers.