Marantz PM-10 Service Manual page 54

[C] PROT_4(FATAL,pin31) is the port for detecting a power amplifier ab-
normality or SMPS abnormality
(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 2.2V (DC), [Q9522, Q9523,
Q9521] will turn on, then the signal from the "PROT_4" will change to "Lo → Hi".
(2) Detection of a rapid drop of voltage in SMPS.
If SMPS ± HV falls below ± 27V, [Q9511, Q9521] turns on and "PROT_4" changes from "Lo → Hi".
When the abnormality mentioned in (1) or (2) is detected, "POW_1 : pin72" and "POW_2 : pin73"
change from "Hi → Lo" and power relay [S8501-S8503] immediately turns off and shuts down.
The STANDBY indicator flickers to inform that an error has occurred.
This protection operation is intended for when a breakdown of the Amplifiers circuit or the SMPS occurs
and immediately shuts off the power in order to avoid the risk of damage.
To check whether the amplifiers circuit or the SMPS is broken, turn off the unit, then wait for about 1
minute and turn it on again.
This action will deactivate the protection operation.
If the "PROT_4" remains in the "Hi"abnormal state, which constitutes an abnormality, the unit shuts
down approximately 4 seconds later and the STANDBY indicator starts flickering.
If the protection operation is not deactivated even after the power is turned on again, the amplifiers
circuit or the SMPS may be broken.
[D] PROT_5(READY,pin40) is the port for detecting abnormalities in the
SMPS and power amplifier
(1) Detection of an abnormality in the power amplifiers power supply circuit ( ± HV).
If undervoltage (around 30V) or overvoltage (around 101V) is detected for the ± HV of the power
amplifier power supply (SMPS), [Q6002, Q6005, Q7002 or Q7005] turns off and "PROT_5" changes
from "Lo → Hi".
(2) Detection of an abnormality in the power amplifiers power supply circuit (VDR).
If undervoltage (around 13.5V) or overvoltage (around 19V) is detected for the VDR of the power
amplifier power supply (SMPS), [Q6002, Q6005, Q7002 or Q7005] turns off and "PROT_5" changes
from "Lo → Hi".
(3) Detection of abnormal temperature increase in the power amplifier.
If an abnormal temperature increase (around 90° C or higher) is detected near the thermistor of the
power amplifier, [Q6002, Q6005, Q7002 or Q7005] turns off and "PROT_5" changes from "Lo → Hi".
(4) Detection of overcurrent in the power amplifier.
When an overcurrent (around 26A or higher) is detected in the power amplifier, [Q6002, Q6005,
Q7002 or Q7005] turns off and "PROT_5" changes from "Lo → Hi".
When the abnormality mentioned in (1) or (4) is detected, "POW_1 : pin72" and "POW_2 : pin73"
change from "Hi → Lo" and power relay [S8501-S8503] immediately turns off and shuts down.
The STANDBY indicator flickers to inform that an error has occurred.
This protection operation is intended for when a breakdown of the Amplifiers circuit or the SMPS occurs
and immediately shuts off the power in order to avoid the risk of damage.
To check whether the amplifiers circuit or the SMPS is broken, turn off the unit, then wait for about 1
minute and turn it on again.
This action will deactivate the protection operation.
If the "PROT_5" remains in the "Hi"abnormal state, which constitutes an abnormality, the unit shuts
down approximately 4 seconds later and the STANDBY indicator starts flickering.
If the protection operation is not deactivated even after the power is turned on again, the amplifiers
circuit or the SMPS may be broken.
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