Sony KV-32HS500 Training Manual page 17

Power-ON Switching Circuit
Reference Figure 3-2 during the following circuit description:
In the Standby mode, System Control (IC2300) is partially powered (using STBY 5V) and waiting for an ON
command from either the Front Panel Controls (IC2300/pins 93 and 94) or the Remote Control (IC2300/pin 7).
Once the ON command is received, IC2300/pin 69 (AC_RLY) outputs a high, which is applied to the base of
Q6527 (turning Q6527 ON). This completes the ground path for the AC Relay (RY6501) and for the base circuit
of Q503.
Q503 turns on and supplies the initial kick voltage and current through D508 to RY6501, closing the relay switch
and supplying AC power to the Main Power Supply through Inrush resistor R6516 and D6530. Once C513 in the
base circuit charges completely Q503 turns off; D508 reverse biases and D509 forward biases, supplying a hold
voltage (9V) to keep the relay switch closed in the ON mode.
At this point the Main Power supply is turning ON (operation will be discussed next). The initial AC power to the
Main Power Supply is through Inrush resistor R6516, which limits the high surge current that occurs momentarily
at turn ON. Once the secondary voltage UNREG 11V is developed on T6502 in the Main Power Supply, it is fed
back to the Inrush Relay (RY6502). RY6502 turns on and bypasses R6516 in the ON mode. R6516 is only in
the circuit during initial power-up of the set.
Troubleshooting Tip:
Obviously, if a failure occurs in the 5V Standby Power Supply the unit will not even attempt to turn ON. If this
condition occurs, check the following components:
1) FH501
2) 13V at IC501 Input Pin (I). If missing, suspect T502, D503 and/or C507.
3) 5V at IC501 Output Pin (O). If missing, suspect a defective IC501.
4) NOTE: Q503 is used as a current source for the AC relay (RY6501). If the collector/emitter junction of
Q503 becomes an Open circuit, the set will still turn ON (using voltage through D509) and function
properly with sufficient AC power input. If the AC power input is weak (Low Voltage ~90VAC, the unit will
have difficulty turning ON without Q503 functioning properly.
3. Power Supply (DA-4 & DA-4X Chassis)
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