Marantz PM-11S3 Service Manual page 14

[B] the PRot_2 (pin53) 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 between +58V and -58V. If the voltage at the
connection point of R8002 and R8003 exceeds DC ±1.2V, Q8001 or Q8002 will turn on to change the signal from the
PROT_2 (pin2) to L from H.
2. Detection of an abnormality in the preamp power supply circuit.
This port monitors the midpoint voltage between +30V and -30V. If the voltage at the connection point of R8123 and
R8124 exceeds DC ±1.2V, Q8003 or Q8004 will turn on to change the signal from the PROT_2 (pin2) to L from H
3. Detection of an abnormality in the function relay power supply circuit.
If the +24VLB of the relay power supply receives an electric current of over 120mA, Q8006 and Q8003 will turn on to
change the signal from the PROT_2 (pin2) to L from H.
If any of the above four abnormalities is detected, the signal from the changing to L from H, the power relay S8502 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 shut
s 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 (pin2) 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.
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