Marantz PM-KI-PEARL-LITE, Руководство по обслуживанию

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15
PROTECTION MODE
Explanation of microprocessor (U101) [PROT-1 (pin6) and PROT-2 (pin7)].
1. The PROT-1 (pin6) is the port to detect the following abnormalities of the Power AMP
(1) Detection of an abnormality in the DC offset voltage from the Speaker Output terminal.
If the voltage from the Speaker Output terminal exceeds approximately 1.2V (DC), Q955 or Q956 will turn on and the
signal from the PROT-1 terminal will change to "L" from "H".
(2) Detection of an abnormal current from the power transistors (Q713 ~ Q716).
If an electric current of over 7A flows in Q713 or Q715, Q951, Q953 and Q957 turn on, and the signal from the
PROT-1 terminal will change to "L" from "H".
If an electric current of over 7A flows in Q714 or Q716, Q952, Q954 and Q957 turn on, and the signal from the
PROT-1 terminal will change to "L" from "H".
(3) Detection of an abnormal temperature of the Heat Sink.
If the temperature of the Heat Sink exceeds approxi110 degrees C, the posistor (R969) will turn on Q958
and the signal from the PROT-1 terminal will change to "L" from "H".
If any of the above three abnormalities is detected, the signal from the PROT-1 terminal will change to "L" from "H", and
the protection circuit will be activated, the signal from the SPK_OUT (pin10) changing to "H" from "L" and the speaker
relays L751, L752 and L753 immediately turned off.
What this protection operation results in after this depends on how long the signal from the PROT-1 has to remain "L".
·
If the PROT-1 (pin6) recovers to "H" within as short a period of time as one second or less.
The MUTE indicator starts flickering, thereby indicates that the protection circuit has come into operation and
automatically turns down the volume. The protection circuit is deactivated after approximately 15 seconds, so
that readjusting the volume will allow normal use of the unit again. This protection operation is intended for the
situation wherein the user has misused the unit temporarily and automatically resets the unit while the amp circuit is
functioning properly.
· If the PROT-1 (pin6) remains "L" for more than one second.
The amp will be powered off by the P_ON (pin15) changing to "H" from "L" and Power relay S851 turned off Then,
the STANDBY indicator flickers, thereby indicating that an error has occurred. This protection operation is intended
for a failure in the amp circuit and immediately turns the power off to avoid the risk of any damage.
Depending on how the user is handling the unit, this operation may be performed no matter if the amp is functioning
properly.
To check if the amp is in order, switch off the unit and switch it on again one minute later. This action will deactivate
the protection operation. If the PROT-1 (pin6) remains "L", which constitutes an abnormality, the unit shuts down
approximately 3 seconds later and the STANDBY indicator starts flickering.
If the protection operation will not be deactivated after the power is turned on again, the amp circuit may be broken.
2. The PROT-2 (pin7) is the port to detect abnormalities of the power supply circuit.
(1) Detection of an abnormality in the power amp power supply circuit.
This port monitors the midpoint voltage of the power amp power supply b49V and -49V. If the voltage at
the connection point of R801 and R802 exceeds DC ±1.2V, Q903 or Q904 will turn on to change the signal from the
PROT-2 (pin7) to "L" from "H".
(2) Detection of an abnormality in the preamp power supply circuit.
Q901 and Q902 monitor the midpoint voltage b28V and -28V. If the voltage at the connection point of R905
and R906 exceeds DC ±1.2V, Q901 or Q902 will turn on to change the signal from the PROT-2 (pin7) to "L" from "H".
(3) Detection of an abnormality in the function relay power supply circuit.
If the +24VL of the relay power supply receives an electric current of over 80 mA, Q815 and Q901 will turn on to
change the signal from the PROT-2 (pin7) to "L" from "H".
If any of the above three abnormalities is detected, the signal from the P_ON (pin15) terminal will be changed to "L" from
"H", the power relay S851 will be turned off and the unit will be shut down. Then, the STANDBY indicator flickers and
indicates that an abnormality has occurred.
This protection operation is intended for a breakdown of the AMP circuit or the power supply circuit and immediately
shuts off the power in order to avoid the risk of damage.
To check if the amp circuit or the power supply circuit is broken, switch off the power and then switch it on again one
minute later. This action will deactivate the protection operation.
If the RPOT-2 (pin7) remains "L" after the power is switched on again, the unit will be shut down again three seconds
later with the STANDBY indicator flickering.
If the unit is powered on again and yet cannot get the protection operation deactivated, the amp circuit or the power
supply circuit may be broken.