31
CIRCUIT DESCRIPTION
Sw+9v and Sw+5v Regulator Operation in Stand-By:
Both of these ICs as well as the STY+11V and the STY+7V regulator ICs are DC to DC converters just
like last year. This is because of the wide range of input voltages from Stand-By to Normal operation of the
Power Supply. The SW+12V regulator (I908) and the SW+5V regulator (I907) are shut off during Stand-
By mode. Q002 and Q903 accomplish this. When the High for the power On/Off pin (53) of the Micro-
processor is inverted by the relay driver Q002, and routed through the PQS1 connector pin (8). This is
detected by Q903, and its collector will go low. This will pull pin (5) of I907 and I908 low, turning off the
two DC to DC converters.
Some Shut-Down Detection Circuits Shut Off During Stand-By:
During Stand-By, all of the secondary voltages are reduced to approximately 50% of their normal voltage,
except the STBY voltages. This could cause a potential problem with the Short Detection circuits for
shutdown. To avoid accidental shut down, Q903 also controls the activity of Q908 and Q909. During
Stand-By, Q903 is turned on. This allows the Base of Q908 to be pulled through D945. This action turns
off Q908. When Q908 is off, it doesnt supply emitter voltage to the collector of Q909. The base of Q909
is connected to 6 Low Detection in-puts, (See the Sub Power Supply Shut Down Circuit explanation and
diagram for further details). When the power supply operates at 50%, the Short Detection circuit could
activate. By turning off Q909, no accidental shut down operation can occur.
ZP94/95 Chassis Has 4 Green and 1 Red LED On Sub Power Supply PWB.
This chassis utilizes 4 Green LEDs in the power supply cold side and a Red LED in the HOT side. The
power supply operates it two different modes, Standby and Projection on mode.
R 907
I903
100% D ead T im e &
IC B + D etection
4
O sc B +
4
R 908
I903 Shutdown
P hotocoupler
Q 905
Shutdown
SC R
D 903 is a R E D L .E.D .
O ff = N o I901 B +
B linking = Shutdown
3
1
2
V cc
16 Shut D own
Inputs
R un
24.2V
24.2V
1.9V
Q 901
Shutdown
SCR
D 903
R
Start U p
R 905
R 906
I901 D river/
O utput IC
R933
Stby
+11V
R930
Stby +7V
Audio
Ft. 29V
R936
Sw
+5V
ZP94/95X CHASSIS L.E.D. (VISUAL TROUBLE DETECTION) DIODES
SUB POW ER SUPPLY PW B 4 GREEN L.E.D.s and 1 RED L.E.D.
ALL GREEN L.E.D.s
D949
G
D927
G
D912
G
D931
G