Sony VPL-PX32 Service Manual page 51

When the potential difference between Pin 8 (CSH) and Pin 9 (CSL) of the control IC exceeds
100 mV due to shorting of the load, etc., the control IC internal current restriction circuit stops PWM
LOGIC and turns OFF the High side MOD-FET.
3. GC Board (SUB5 V DC-DC converter)
The GC board is input with the secondary side output voltage (9.0 ± 2.0 V) of T2101 from when the
power supply voltage is input. It steps down the standby voltage 5.0 ± 0.3 V supplied to the micropro-
cessor by the DC-DC converter (IC2500) and outputs it.
The GB board receives and transmits the POWER ON signal, and POWER PROT signal.
4. GB Board (D3.3 V DC-DC Converter)
The GB board is input with the secondary side output voltage A6 V (5.9 ± 0.3 V) of T2100 when the
power is turned ON. It steps-down the D3.3 V (3.3 ± 0.3 V) supplied to the signal circuit using the
DC-DC converter (IC2300), and outputs it.
5. GD Board 10.7 V DC-DC Converter and FAN+B1, 2 Regulator
The GD board is input with the secondary side output voltage 17.5 V (17.5 ± 0.4 V) of T2100 when
the power is turned ON. It steps-down the 10.7 V (10.6 ± 0.3 V) supplied to the signal circuit using
the DC-DC converter (IC2700), and outputs it.
The GD board is mounted with a regulator (IC2701, IC2702) which inputs the above 10.7 V and
steps-down the voltage FAN+B1, 2 for the suction and exhaust FAN. The microprocessor of the Y
board reads the resistance value of the thermistor (TH2020) (resistance value changes according to
the temperature) mounted on the S board and outputs the 0 to 5 V voltage from the port to Pins 7 and
9 of CN2701 of the GD board.
By adding the current based on the voltage to the ADJ terminal of the regulators (IC2701 and
IC2702), the suction FAN controls the 10.2 V to 6 V (FAN+B1) while the exhaust FAN controls the
10.2 V to 7 V (FAN+B2) voltage. The thermistor TH2020 mainly monitors the external temperature
of the unit. When the LAMP MODE STANDARD mode is selected on the menu, both fans are set to
the minimum voltage of FAN 7 V for the suction FAN and 8 V for the exhaust Fan. When the LAMP
MODE LOW mode is set, the fans are set to the minimum voltage of FAN 6 V for the suction FAN
and 7 V for the exhaust Fan.
VPL-PX32
3-23