Hitachi 51SWX20B Training page 13

DP-2X POWER ON RELAY CONTROLS EXPLANATION
RELAYS ENERGIZED BY Q907: Activated by Power _1
•
S901
This completes the path for AC to reach the High Voltage power supply bridge diode D902. (See the
High Voltage Regulation Circuit for details). This action start the High Voltage power supply
SW+115V for the deflection circuit.
•
S902
This completes the path for the pulse generated from pin 14 of T901, (+38V) to reach the Audio B+ rec-
tifier diode D944. Here the Audio +38V is generated and output from the PPS5 connector pins 1, 2 and
3 and on to the Audio output circuit.
•
S903
This completes the path for the pulse generated from pin 10 of T901 (Control +6V), rectified by diode
D941 which produces SW+6V to reach the PPS4 connector pins 7 and 6 and on to IP52 (Switched
+3.3V regulator) and IP53 (Switched +5V regulator) on the Signal PWB.
Power _2: (High when the set is turned On and/or when the Timer is On).
•
When the Customer presses the Power On button on the Front control panel or the Remote control, the
Microprocessor I001 output a High from pin 58. This high is routed to two different circuits.
•
DM +9V REGULATOR:
•
When Power _2 goes high, it's routed to pin 2 of IP01 on the Signal PWB. This is the DM +9V regula-
tor and it turns on. Input to pin 5 is the DM +10V, IP01 regulates this down to 9V and output it from pin
3 to the Digital Module (ATSC Tuner) pin 12 PMS1.
•
The DM +9V is also routed to the Terminal PWB pin 21of the PST2 connector. This turns on the Selec-
tor IC IX01 and the Monitor Out Circuit.
•
Power _2 is also routed to the PPS3 connector pin 4 and then to the Power Supply. This high is routed
to the base of Q909 turning it On.
•
When Q909 turns on, it causes the following relays to energize.
RELAYS ENERGIZED BY Q909: Activated by Power _2
•
S905
This completes the path for the pulse generated from pin 13 of T901 (+35V) to reach the Tuning Volt-
age B+ rectifier diode D943. Here the SW+35V is generated and output from the PPS3 connector pin 8
and on to the Tuners pin 9. This voltage is also routed out the PPS7 connector pin 6 DM +28V, to be-
come tuning voltage for the Digital Tuner (ATSC) via pin 1 of the PMS2 connector.
•
S906
This completes the path for the pulse generated from pin 17 (Digital Module +10V) of T901 to reach the
rectifier diode D945. Here the DM +10V is generated and output from the PPS7 connector pin 2 and 3
and on to the DM +9V regulator IP01. Input to pin 5, IP01 regulates this down to +9V and outputs it
from pin 3 to the Digital Module (ATSC Tuner) pin 12 of the PMS1 connector.
TIMER (Unattended Recording) OPERATION:
NOTE: Power _2 is also high when the Timer is set for unattended recordings. When the Timer is activated, the
Tuners, Selector IC and Monitor output become active. During this time, Power_1 remains Low.
This way, the Selector IC, Tuners, Audio Circuit and Monitor outputs remain active.
The Table below shows the logic state of Power _1 and Power _2.
MODE
Stand By
Timer
Power ON
POWER _1
L
L
H
POWER _2
L
H
H
PAGE 01-05