Hitachi 46W500, Training

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DP-3X POWER SUPPLY SHUT DOWN EXPLANATION
PAGE 01-07
The next explanation discusses the Cold Ground side shut down circuit operation.
This explains the Power Supply Shut Down Circuit Diagram:
See DP-3X Power Supply Shut Down Diagram for details
Use this explanation and Diagram in conjunction with the following diagrams;
DP-3X Deflection Protect Power Supply Shut Down Circuit Diagram and
DP-3X PROT_CPT and PROT_SW Shut Down Circuit Diagram.
The Power supply is centered around the Switching Transformer T901 and the driver IC, I901.
This power supply creates voltages that are Switched on when the Set is turned on.
1. Audio SW +30V 2. SW +10V
3. +220V 4. SW+28V
5. SW -28V 6. SW +115V
Other supplies are generated from these 6 main voltages.
Q904 Relay Inhibit Activation. (SHUT DOWN) called COMMON ACTION CIRCUIT.
All Shut Down events will cause the main power relay to turn off. This action will stop all secondary power supplies.
The Low Voltage power supply (Stand-By) continues to operate.
If any of the
23 shut down circuits activate, the base of Q904 will go High. This turns on Q903 and removes the Power On
High from PPS4 connector pin 7 called Power_1 and the main power supply will STOP. Q903 operates as a “latch”. This
prevents Q904 from turning off is the shut down signal disappears after shutdown.
SOME SHUTDOWN CIRCUITS ARE DEFEATED IN STANDBY MODE. (Set Off).
When the set is turned off or in Stand By, 12 of the shut down inputs are not active.
•
Shorted SW+35V (from voltage divider R940 and R941 off the SW+115V from pin 11 of T901 ). This voltage is
monitored by D938 .
•
Shorted SW+10V (from pin 16 of T901 ). This voltage is monitored by D939 .
•
Shorted SW+5.5V (from pin 1 of I905 ) This voltage is monitored by D940 .
•
Shorted 220V (from pin 10 of T901 ) This voltage is monitored by D941 and D942 .
•
Shorted SW+6.3V (from pin 1 of I906 ) This voltage is monitored by D943 .
•
Prot_SW (6 shut down inputs) This voltage is monitored by D944 .
1. SW +2.2V 2. SW +3.3V
3. SW +5V 4. SW +9V
5. SW +9.3V 6. Blue CRT VM 220V excessive current sensing circuit.
•
Shorted SW+28V (from pin 15 of T901 ) This voltage is monitored by D943 .
These shut down circuits are defeated because the SW (Switched) power supplies are turned off in standby. So to prevent
faults triggering of the shutdown circuit, the sensing circuits are turned off also..
Q906
supplies the high for shutdown if any of the shut down circuit attached to its base become low.
Q906
requires emitter
voltage to operated. Emitter voltage is supplied from the SW +6.3V and SW +10V line. This voltage must be active for Q906
to function. When the set is turned off these switched voltages disappear, so Q906 can no longer operate.
COLD GROUND SIDE SHUT DOWN INPUTS EXPLAINED
GENERAL INFORMATION (See previous pages for generic circuit details):
All of the Power Supply Shutdown circuitry can be broken down into the following categories;
•
Voltage Missing Detection or Short Detection or Negative Voltage Loss Detection
•
Voltage Too High Detection
•
Excessive Current Detection
(Continued on page 8)