Hitachi 51SWX20B Installation guide

CONTENTS... 2002 DP-2X Chassis Projection Television Information
INSTRUCTOR… Alvie Rodgers C.E.T. (Chamblee, GA.)
Dec 2004(ver g)Training Materials Prepared by: ALVIE RODGERS C.E.T.
2002 and 2003
MODEL RELEASE
DIGITAL
HD READY PTV
Chassis Model # Aspect
DP-27 51SWX20B 16X9
57SWX20B
65SWX20B
DP-27D 57TWX20B 16X9
65TWX20B
DP-26 65XWX20B 16X9
57XWX20B
51XWX20B
DP-24 43FWX20B 16X9
DP-23G 57GWX20B 16X9
51GWX20B
DP-23K 46F500 16X9
DP-23 57UWX20B 16X9
57F500
57G500
51UWX20B
51F500
51G500

THIS PAGE LEFT BLANK

DP-2X TABLE OF CONTENTS
Table of Contents Page 1 of 4
Dec 2004(ver f)Materials prepared by
Alvie Rodgers C.E.T.
TOPICS PAGE
Continued on Next Page
SECTION (1) POWER SUPPLY DIAGRAMS:
•+6V Lo Voltage Regulation Circuit Diagram Explained ------------------------------------------ 01-01
•+6V Lo Voltage Regulation Circuit Diagram DP-26 and DP-27 ------------------------------------- 01-02
•+6V Lo Voltage Regulation Circuit Diagram DP-23, DP-23G and DP-24---------------------------- 01-03
•Power On Relay Controls Circuit Diagram Explained --------------------------------------------- 01-04
•Power On Relay Controls Circuit Diagram DP-23, DP-23G and DP-24------------------------------- 01-06
•Power On Relay Controls Circuit Diagram DP-26 --------------------------------------------------- 01-07
•Power On Relay Controls Circuit Diagram DP-27 and DP-27D ------------------------------------- 01-08
•Low Voltage Shut Down Circuit Diagram Explained --------------------------------------------- 01-09
•Low Voltage Shut Down Circuit Diagram ----------------------------------------------------------- 01-13
•SW +115V Hi Voltage Regulation Circuit Diagram Explained ---------------------------------- 01-14
•SW +115V Hi Voltage Regulation Circuit Diagram ----------------------------------------------- 01-15
•Additional Hi Voltage Shut Down Circuit Diagram Explained ----------------------------------- 01-16
•Additional Hi Voltage Shut Down Circuit Diagram ------------------------------------------------ 01-17
•Protect (Deflection) Hi Volt Shut Down Circuit Diagram Explained --------------------------- 01-18
•Protect (Deflection) Hi Volt Shut Down Circuit Diagram ---------------------------------------- 01-19
•LEDs (Visual Trouble Shooting) Lo Voltage Power Supply Circuit Diagram Explained ---- 01-20
•LEDs (Visual Trouble Shooting) Circuit Diagram DP-23, 23G and DP-24 ------------------------------- 01-21
•LEDs (Visual Trouble Shooting) Circuit Diagram DP-26 ------------------------------------------------ 01-22
•LEDs (Visual Trouble Shooting) Circuit Diagram DP-27 and DP-27D ----------------------------------- 01-23
SECTION (2) MICROPROCESSOR INFORMATION:
•Microprocessor DATA COMMUNICATION Explanation ------------------------------------- 02-01
•Microprocessor DATA COMMUNICATION Circuit Diagram DP-23, 23G, 24, 27 & 27D ---------- 02-04
•Microprocessor DATA COMMUNICATION Circuit Diagram DP-26------------------------------ 02-05
•Microprocessor Sync Input Circuit Diagram Explained ----------------------------------------- 02-06
•Microprocessor Sync Input Circuit Diagram Circuit Diagram DP-23, 23G, 27 & 27D ---------------- 02-07
•Microprocessor Sync Input Circuit Diagram Circuit Diagram DP-24 -------------------------------- 02-08
•Microprocessor Sync Input Circuit Diagram Circuit Diagram DP-26 -------------------------------- 02-09
SECTION (3) VIDEO CIRCUIT INFORMATION:
•Video NTSC Circuit Diagram Explained ----------------------------------------------------------- 03-01
•Video NTSC Circuit Diagram Circuit Diagram DP-23, 23G, 27 & 27D -------------------------------- 03-03
•Video NTSC Circuit Diagram Circuit Diagram DP-24 ------------------------------------------------ 03-04
•Video NTSC Circuit Diagram Circuit Diagram DP-26 ------------------------------------------------ 03-05
•Video Component, OSD & NTSC Circuit Diagram Explanation -------------------------------- 03-06
•Video Component, OSD & NTSC Circuit Diagram DP-23, 23G, 27 & 27D ------------------------ 03-08
•Video Component, OSD & NTSC Circuit Diagram DP-24 ---------------------------------------- 03-09
•Video Component, OSD & NTSC Circuit Diagram DP-26 ---------------------------------------- 03-10
•ATSC (Digital Tuner) Block Diagram DP-26 Only ------------------------------------------------- 03-11

DP-2X TABLE OF CONTENTS
Table of Contents Page 2 of 4
Dec 2003 (ver g)Materials prepared by
Alvie Rodgers C.E.T.
TOPICS PAGE
Continued on Next Page
SECTION (3) VIDEO CIRCUIT INFORMATION: (Continued)
•Rainforest IC Pulse Explanation Explained-------------------------------------------------------- 03-12
•ABL Circuit Diagram Explanation ------------------------------------------------------------------- 03-13
•ABL Circuit Diagram ---------------------------------------------------------------------------------- 03-14
•ABL Switch (Black Side Bars) Circuit Diagram and Explanation ------------------------------ 03-15
•Audio Video Mute Circuit Diagram Explanation ------------------------------------------------- 03-16
•Audio Video Mute Circuit Diagram ----------------------------------------------------------------- 03-18
•DVI Input Circuit Diagram ---------------------------------------------------------------------------- 03-19
•Component Sync Circuit Diagram Explanation ----------------------------------------------------- 03-20
•Component Sync Circuit Diagram --------------------------------------------------------------------- 03-21
SECTION (4) AUDIO CIRCUIT INFORMATION:
•Audio Main Terminal Circuit Diagram Explanation ---------------------------------------------- 04-01
•Audio Main Terminal Circuit Diagram ------------------------------------------------------------- 04-02
SECTION (5) DEFLECTION CIRCUIT:
•Horizontal Drive Circuit Diagram Explanation --------------------------------------------------- 05-01
•Horizontal Drive Circuit Diagram ------------------------------------------------------------------ 05-03
•IH01 Horizontal Drive IC Voltages and Waveforms (Also, Not Running Info.) ------------ 05-04
•Sweep Loss Detection Circuit Diagram Explanation ---------------------------------------------- 05-05
•Sweep Loss Detection Circuit Diagram ------------------------------------------------------------- 05-06
•Vertical Output Circuit Diagram Explanation ---------------------------------------------------- 05-07
•Vertical Output Circuit Diagram -------------------------------------------------------------------- 05-08
•Pincushion Circuit Diagram-------------------------------------------------------------------------- 05-09
•Pincushion Circuit Diagram-------------------------------------------------------------------------- 05-10
SECTION (6) DIGITAL CONVERGENCE CIRCUIT INFORMATION:
•Digital Convergence Interconnect Circuit Diagram Explanation ------------------------------ 06-01
•Digital Convergence Interconnect Circuit Diagram DP-23, 23G, 26, 27 & 27D ----------------------- 06-05
•Digital Convergence Interconnect Circuit Diagram DP-24 ------------------------------------------ 06-06
•Remote CLU4321UG (Digital Convergence Mode Functions) DP-23, DP-23G & DP-24 -------- 06-07
•Remote CLU5721TSI (Digital Convergence Mode Functions) DP-26 -------------------------- 06-08
•Remote CLU5722TSI (Digital Convergence Mode Functions) DP-27 -------------------------- 06-09
•43" Overlay Dimensions ----------------------------------------------------------------------------- 06-10
•46" Overlay Dimensions ----------------------------------------------------------------------------- 06-11
•51" Overlay Dimensions ----------------------------------------------------------------------------- 06-12
•57" Overlay Dimensions ----------------------------------------------------------------------------- 06-13
•65" Overlay Dimensions ----------------------------------------------------------------------------- 06-14
SECTION (7) ADJUSTMENT INFORMATION:
•Adjustment Order ------------------------------------------------------------------------------------ 07-01
•Pre Heat Run ------------------------------------------------------------------------------------------ 07-02
•Cut Off Adjustment ----------------------------------------------------------------------------------- 07-03
•Pre-Focus Adjustment -------------------------------------------------------------------------------- 07-04

DP-2X TABLE OF CONTENTS
Table of Contents Page 3 of 4
Dec 2003 (ver f)Materials prepared by
Alvie Rodgers C.E.T.
TOPICS PAGE
SECTION (7) ADJUSTMENT INFORMATION (Continued):
•DCU Crosshatch Phase Settings ------------------------------------------------------------------- 07-05
•Horizontal Position (Coarse) Adjustment --------------------------------------------------------- 07-06
•Raster Tilt Adjustment ------------------------------------------------------------------------------- 07-07
•Beam Alignment Adjustment ------------------------------------------------------------------------ 07-08
•Off-Set for Red and Blue Raster Position Adjustment ----------------------------------------- 07-09
•Vertical Size Adjustment ----------------------------------------------------------------------------- 07-10
•Horizontal Size Adjustment -------------------------------------------------------------------------- 07-11
•Beam Form Adjustment ------------------------------------------------------------------------------ 07-12
•Lens Focus Adjustment ------------------------------------------------------------------------------- 07-13
•Static Focus Adjustment ------------------------------------------------------------------------------ 07-14
•DCU Character Set-Up and DCU Data Confirmation Adjustment -------------------------- 07-15
•DCU Pattern (Sensor Position) Set-Up Adjustment --------------------------------------------- 07-16
•43" Overlay Dimensions ----------------------------------------------------------------------------- 07-17
•51" Overlay Dimensions ----------------------------------------------------------------------------- 07-18
•57" Overlay Dimensions ----------------------------------------------------------------------------- 07-19
•65" Overlay Dimensions ----------------------------------------------------------------------------- 07-20
•Remote CLU5721TSI (Digital Convergence Mode Functions) --------------------------------- 07-21
•Remote CLU5722TSI (Digital Convergence Mode Functions) --------------------------------- 07-22
•Remote CLU4321UG (Digital Convergence Mode Functions) ---------------------------------- 07-23
•Read from ROM Notes ------------------------------------------------------------------------------ 07-24
◊DIGITAL CONVERGENCE ALIGNMENT PROCEDURE ------------------------------ 07-25
◊(Clearing RAM) Clearing Digital Convergence Data -------------------------------------------- 07-25
◊Centering Magnet Adjustment ---------------------------------------------------------------------- 07-25
◊Static Centering Adjustment (Freeze Button)------------------------------------------------------ 07-26
◊Green 3X3 Mode Adjustment ------------------------------------------------------------------------ 07-27
◊Red and Blue 3X3 Mode Adjustment --------------------------------------------------------------- 07-28
◊Green 7X5 Mode Adjustment ------------------------------------------------------------------------ 07-29
◊Red and Blue 7X5 Mode Adjustment --------------------------------------------------------------- 07-30
◊Green 9X13 Mode Adjustment ----------------------------------------------------------------------- 07-31
◊Red and Blue 9X13 Mode Adjustment -------------------------------------------------------------- 07-32
◊Storing Digital Convergence Data (Write to ROM)---------------------------------------------- 07-33
◊Initializing Magic Focus Sensors ------------------------------------------------------------------- 07-34
◊Convergence Touch Up Minor Adjustments ------------------------------------------------------ 07-35
◊ERROR CODES for DCU HD FOCUS Description-------------------------------------------- 07-36
•Blue De-Focus Adjustment --------------------------------------------------------------------------- 07-37
•White Balance and Sub Brightness Adjustment ------------------------------------------------- 07-38
•White Balance Adjustment Flow Chart ------------------------------------------------------------ 07-39
•Sub Picture (PIP) Amplitude Adjustment --------------------------------------------------------- 07-40
•Horizontal Position (Fine) Adjustment ------------------------------------------------------------- 07-41
•Magnet Locations ------------------------------------------------------------------------------------- 07-42
Continued on Next Page

DP-2X TABLE OF CONTENTS
Table of Contents Page 4 of 4
Dec 2003(ver f)Materials prepared by
Alvie Rodgers C.E.T.
TOPICS PAGE
SECTION (8) MISCELLANEOUS INFORMATION:
•Rear Panel DP-27 and DP-27D (Terminal Input) Drawing -------------------------------------- 08-01
•Rear Panel DP-23 and DP-23G (Terminal Input) Drawing -------------------------------------- 08-02
•Rear Panel DP-26 (Terminal Input) Drawing ----------------------------------------------------- 08-03
•Rear Panel DP-24 (43FWX20B Only Terminal Input) Drawing ------------------------------- 08-04
•Signal PWB Drawing --------------------------------------------------------------------------------- 08-05
•Deflection PWB Drawing ---------------------------------------------------------------------------- 08-06
•Power Supply PWB Drawing ----------------------------------------------------------------------- 08-07
•CRT PWBs Drawing ---------------------------------------------------------------------------------- 08-08
•All but DP-24 Front Control PWBs Drawing ---------------------------------------------------- 08-09
•DP-24 Front Control PWBs Drawing -------------------------------------------------------------- 08-10
SECTION (9) THINGS YOU SHOULD KNOW / SERVICE BULLETINS / ETC….:
•This section changes often, the index for this section is shown on the
Things You Should Know section divider.
Please go to Section 9 section divider cover page for details------------------------------------- 09-00
•Download this Section Separately.

DP-2X
CHASSIS DIAGRAMS
POWER SUPPLY
INFORMATION
SECTION 1

THIS PAGE LEFT BLANK

DP-2X +6V POWER SUPPLY REGULATION EXPLANATION
PAGE 01-01
+6V Power Supply Circuit Diagram explanation: The Primary Chassis Discussed is the DP-27 and DP-27D.
(See DP-26, DP-27 and DP-27D +6V Regulation Circuit Diagram for details).
(Also, see DP-23, DP-23G and DP-24 +6V Regulation Circuit Diagram for details).
Note: Items described below for the DP-23, 23G and DP-24 are shown in brackets [ ].
THIS POWER SUPPLY RUNS ALL THE TIME:
When a Projection set is plugged into an AC outlet, it must produce a power supply to energize certain circuits.
These circuits are responsible for monitoring the Infrared input or Front control Keys as well as the Auxiliary
inputs if the Auto Link feature is active.
These power supplies are generally labeled as Always power supplies or Standby power supplies. As an example
A+6V would indicate a +6V power supply that’s always present. If the power supply has an Sby prefix, (example
Sby +6V) this too is always present if the set is plugged into the AC outlet.
The DP-2X power supply Standby voltages are regulated by monitoring the Control +6V which becomes the
Sby +5V after it is regulated by I909.
The Control +6V is generated on the Secondary of T901 pin 10 [7]. The pulse is rectified by D941 and filtered
by C954 and becomes a +6V Power Supply.
REGULATION: Note: Items for the DP-23, 23G and DP-24 are shown in brackets [ ].
The primary route for the Control +6V is to pin 3of I909 and output as Sby. +5V from pin 2.
However, the regulation route is to pin 1of I904. Internally, the LED is illuminated by degrees dependant upon
the Control +6V voltage fluctuations. The internal receiver receives this light and acts as a variable resistor from
pin 4to pin 3ground. This action causes pin 6of I901 to manipulate the internal oscillator within I901. This in
turn causes the frequency of the drive pulse delivered to the Gate of the internal SMOSFET (Switch Metal Oxide
Semiconductor Field Effect Transistor) to manipulate the frequency of the pulse generated on the primary of
T901. Pin 6 [3] of T901 is routed to pin 1of I901 which is the Drain of the SMOSFET. The source is connected
internally to pin 2and then to floating ground pin 9 [6] of T901. The floating ground is monitored by three [two]
low ohm resistors, R908, R909 and R910 [R908, R909] to hot ground. Here, the current drain of the internal
SMOSFET is monitored. If this current exceeds a specific value, the voltage developed by these low ohm resis-
tors is routed back into pin 5 which is the Over Current Protection circuit. This pin will inhibit the drive signal to
the gate of the SMOSFET. As soon as the excessive current situation is eliminated, the IC will recover and con-
tinue functioning.
B+ GENERATION FOR THE LOW VOLTAGE POWER SUPPLY DRIVER IC:
Vcc for the Driver IC is first generated by the AC input. This voltage is called Start Up Voltage. I901 requires
16V DC to operate normal. However, it will begin operation at 6.8V DC on pin 3of I901.
When AC is applied, AC is routed through the main fuse F901 (a 6 Amp fuse), then through the Line filter L901
to prevent any internal high frequency radiation for radiating back into the AC power line. After passing the fil-
ters it arrives at the main full wave bridge rectifier D901 where it is converted to Raw 150V DC voltage to be
supplied to the power supply switching transformer T901 pin 2[1].
However, one leg of the AC is routed to a half wave rectifier D904 where it is rectified, routed through R906 and
R907 (both a 68K ohm resistor), filtered by C911, clamped by a 30V Zener D907 and made available to pin (3)
of I901 as start up voltage. When this voltage reaches 6.8Vdc, the internal Regulator of I901 is turned On and
begins the operation of I901.
When the power supply begins to operate by turning on and off the internal Switch MOS FET, the Raw 150V DC
routed through T901, to I901 in on pin 1(Drain) and out on pin 2which is the Source. The Source of the internal
Switch MOS FET is routed out of pin 2through three low ohm resistors to hot ground. When the internal Switch
MOS FET turns on, it causes the transformer to saturate building up the magnet field. When the internal Switch
MOS FET turns off, the magnet field collapses and the EMF is coupled over to the secondary windings, as well
as the drive windings. The drive windings at pin 8 [5] of T901 produce a run voltage pulse which is rectified by
D905, filtered by C911 then routed clamped by D907 and now becomes run voltage (16V) for I901 pin 3.
Note too that Hot Ground is the Negative Leg of the bridge rectifier D901 and the Floating Ground is pin 9 [6] of
T901.

D901
DP-26, DP-27 and DP-27D CHASSIS POWER SUPPLY Sby +6V REGULATION
Lo Voltage Power Supply
PAGE 01-02
R913
Run
Start Up
Osc B+
16.3V
3
R907
R906
D905
7
D910
R914
R911
PPS3
2
0.0685A
Sby +5V
10
T901
11
C969
C954
D941
8
T902
9
C916
BD
1
2
R912
150V
F902
2
6
T901
R908
R909
R910
0.47
Ohm
D
S
D904
D906
C914
I901
Driver/
Output IC
OCP
Control
+6V
I909
+5V
Reg
3 2
1
C985C972 C973
I904
Regulator Photocoupler
3
R915
Hot Ground from
negative leg of
Bridge D901
FB
1
2
R958
R957
D953
4
FB/OLP
6
D908
C918
R916
C917
R917
1.79A
Cold Ground Pin 11
Secondary of
T901
C904
Floating Ground
from pin 9 of T901
C915
4
ABS
5
D907
C911
C910A
AC

R914
C916
R912
C914
D901
DP-23, DP- 23G and DP-24 Chassis
+6.0 V Low Voltage Regulation
R913
Run
Start Up
Osc B+
16.3V
3
R907
R906
D905
7
D910
R911
PPS3
2
0.0685A
Sby +5V
7
T901
8
C969
C954
D941
5
T901
6
BD
1
2
150V
F902
1
3
T901
R908
R909
0.47
Ohm
D
S
D904
D906
I901
Driver/
Output IC
OCP
Control
+6V
I909
+5V
Reg
3 2
1
C985
C972 C973
I904
Regulator Photocoupler
3
R915
Hot Ground from
negative leg of
Bridge D901
FB
1
2
R958
R957
D953
4
FB/OLP
6
D908
C918
R916
C917
R917
1.79A
Cold Ground from
pin 8 of T901
C904
Floating Ground
from pin 6 of T901
C915
4
ABS
5
D907
C911
C910A
AC
C913
PAGE 01-03

DP-2X POWER ON RELAY CONTROLS EXPLANATION
PAGE 01-04
Relay Controls Circuit Diagram explanation:
(See DP-23, DP-23G, DP-24 and DP-27, DP-27D Relay Controls Circuit Diagram for details)
POWER ON:
When the Customer presses the Power On button on the Front control panel or the Remote control, the Micro-
processor I001 output a High from pin 59. This high is routed to the base of Q026 which turns this transistor On
and it’s collector connected to the Sty +5V line goes low. This action in turn causes the base of Q025 to go low
and turns Q025 to turn Off. Q025 collector is also connected to the Sby +5V line and it’s collector pulls up to
5V.
This high is routed to the PPS3 connector pin 4. Provided the Short Detection transistor Q903 isn’t activated,
(See the Lo Voltage Power Supply Shut Down Circuit for details), then the High from pin 4is routed to the base
of Q908 turning it On.
When Q908 turns on, it’s collector is connected to the Sby +5V line. It’s emitter pulls up and supplies a high to
the base of Q907 turning it On. When Q907 turns on, it causes the following relays to energize.
RELAYS ENERGIZED BY Q907 (DP-23, DP-23G, DP-24, DP-27 and DP-27D:
Note: This description refers specifically to the DP-27 and DP-27D chassis. Components identified inside brack-
ets [ ] are for the DP-23, 23G and DP-24 chassis.
S901
This completes the path for AC to reach the High Voltage power supply bridge diode D902. (See the High Volt-
age Regulation Circuit for details). This action starts the High Voltage power supply SW+115V for the deflection
circuit.
S902
This completes the path for the pulse generated from pin 14 [11] of T901, (+38V for DP-26, DP-27 and DP-27D)
and [+29V for DP-23, DP-23G and DP-24] to reach the Audio B+ rectifier diode D944. Here the Audio +38V
[+29V] is generated and output from the PPS5 connector pins 1, 2and 3and on to the Audio output circuit.
S903
This completes the path for the pulse generated from pin 10 [7] of T901 (Control +6V), rectified by diode D941
which produces SW+6V to reach the PPS4 connector pins 7and 6and on to IP52 (Switched +3.3V regulator)
and IP53 (Switched +5V regulator) on the Signal PWB.
S905
This completes the path for the pulse generated from pin 13 [10] of T901 (+35V) to reach the Tuning Voltage B+
rectifier diode D943. Here the SW+35V is generated and output from the PPS3 connector pin 8and on to the
Tuners pin 9.
DP-26 ONLY: RELAYS ENERGIZED BY POWER _1 and POWER _2:
(See DP-26 Relay Controls Circuit Diagram for details)
Power _1: (High when the Set is turned 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 59. This high is routed to the base of Q026 which turns this
transistor On and it’s collector connected to the Sty +5V line goes low. This action in turn causes the
base of Q025 to go low and turns Q025 to turn Off. Q025 collector is also connected to the Sby +5V
line and it’s collector pulls up to 5V.
•This high is routed to the PPS3 connector pin 4. Provided the Short Detection transistor Q904 isn’t ac-
tivated, (See the Lo Voltage Power Supply Shut Down Circuit for details), then the High from pin 4is
routed to the base of Q907 turning it On.
•When Q907 turns on, it causes the following relays to energize.
(Continued on page 5)

DP-2X POWER ON RELAY CONTROLS EXPLANATION
PAGE 01-05
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, 2and
3and 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 7and 6and 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 2of 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
3to 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 6DM +28V, to be-
come tuning voltage for the Digital Tuner (ATSC) via pin 1of 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 3to 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 POWER _1 POWER _2
Stand By L L
Timer L H
Power ON H H

S-905 SW +35V
Supply Relay
1.30A
DP-23, DP-23G and DP-24 Chassis Power On Relay Controls
GREEN L.E.D.
Audio + 29V
D944
T901
C962
L922
C957
C978
PPS5
1 2
E911
S-902 Audio Power
Supply Relay
3 4
Sby +5V
C961 C956
PPS3
8
0.0165A
Audio Gnd
12 11
SW + 35V
10
L921
R992
3 7
Gnd Gnd
5 6 7
L923 PPS4
6
1.33A
SW + 6V
7
S-903 SW +6V
Supply Relay
4 3
Gnd Gnd
C957 R961
R962 R963 4
POWER _1
Q903 Short Det.
See Power Supply Shut Down Circuit
Q908
Q907
D954 R960
R959
D943
5Gnd
Off
On
Audio Gnd Audio Gnd Audio Gnd
+35V +29V
R985
D965
8
S-901 Main
Power Relay
AC
AC to D902
High Voltage
Power Supply
Sby 5V comes from I909 pin 2
Sby +5V
2
Sby +5V
7
Q025 Q026
59 I001
Micro
T901
PAGE 01-06
C959
D941
C954
Control +6V
On Off

R963
0.25 A From I909
DM +28V
Audio + 38V
Audio
+38V 1.55A
GREEN L.E.D.
D944
T901
C952
C957
PPS5
1 2
S-902
SW +35V Relay
3 4
Sby +5V
Audio Gnd
15 14
5 6 7
Audio Gnd Audio Gnd Audio Gnd
R985 D965
Sby 5V comes
from I909 pin 3
C961
C956
PPS3
1
1.30A
SW + 35V
3 7
Gnd Gnd
C959
L923
PPS4
6
1.54A
10
S-903 SW +6V
Supply Relay
4 3
Gnd Gnd
C957
R962 R963 4
POWER _1
Q904
Short Det.
See Power Supply
Shut Down Circuit
Q907
D954 R960
R959
D941
C954
7 5Gnd
Off
On
+35V
Control +6V
11
S-901 Main
Power Relay
AC
AC to D902
High Voltage
Power Supply
Sby +5V
2
T901
S-905 SW +35V
Supply Relay
D943
1.55 A
D945
T901 C963
C958
PPS7
2
1
E912
S-906 Digital
Module 10 V Relay
3 4
Sby +5V
Audio Gnd
16 17
5 6 7
Audio Gnd N/C
Sby +10V
DM +10V
DM +10V
DP-26 RELAY CONTROLS
Q909
L922
C978
L921
R992
0.36 A
From D942
0.006 A
5
POWER _2
C968 R984
D972
2
SW + 9V
1
1.06A
SBY + 5V
Off
On
From Micro Pin 59 From Micro Pin 58
SW + 6V
From I911
MODE
Stand By
Timer
TV On
POWER
_1
L L
H
POWER
_2
L
H H
13
E911
On Off
PAGE 01-07
R973

S-905 SW +35V
Supply Relay
1.95A
DP-27 and DP-27D CHASSIS RELAY CONTROLS on the POWER SUPPLY
GREEN L.E.D.
Audio + 38V
D944
T901
C962
L922
C957
C978
PPS5
1 2
E911
S-902 Audio Power
Supply Relay
3 4
Sby +5V
C961 C956
PPS3
8
0.0165A
Audio Gnd
15 14
SW + 35V
13
L921
R992
3 7
Gnd Gnd
5 6 7
L923 PPS4
6
1.33A
SW + 6V
10
S-903 SW +6V
Supply Relay
4 3
Gnd Gnd
C957 R961
R962 R963 4
POWER _1
Q903 Short Det.
See Power Supply Shut Down Circuit
Q908
Q907
D954 R960
R959
D943
5Gnd
Off
On
Audio Gnd Audio Gnd Audio Gnd
+35V +38V
R985
D965
11
S-901 Main
Power Relay
AC
AC to D902
High Voltage
Power Supply
Sby 5V comes from I909 pin 3
Sby +5V
2
Sby +5V
7
Q025 Q026
59 I001
Micro
C959
D941
C954
Control +6V
On Off
PAGE 01-08

DP-2X LOW VOLTAGE POWER SHUT DOWN EXPLANATION
Low Voltage Power Supply Shut Down Circuit Diagram explanation:
(See DP-27 Signal Power Supply (Low Voltage) Shut-Down Circuit Diagram for details)
The Low Voltage power supply is centered around the Switching Transformer T901 and I901.
This power supply creates the Standby voltages SBY +5V which runs anytime the set is plugged into an AC out-
let. It also creates other voltages that are Switched on when the Set is turned on.
Audio +38V
SW +35V
SW +9V
SW +HVcc
The following explanation will describe the Low Voltage Power Supply Shut Down Circuit.
POWER SUPPLY SHUTDOWN PHOTO COUPLER I905 EXPLANATION
This chassis utilizes I901 as the Osc.\Driver \Switch for the Low Voltage power supply, just as the previous chas-
sis have done. The Shutdown circuit, (cold ground side detection), removes I901 B+ at pin 3 via the following
circuit, I905 (the Photo Coupler), which isolates the Hot ground from the Cold ground and couples the Shutdown
signal to the Hot Ground side, Q902 on the hot ground side and Q901 which latches Q902 on. When Q902 is on,
it removes B+ from pin (3) of I901 (the Vin pin).
The Power Supply utilizes a Shutdown circuit that can trigger Q902 from 2input sources. (1 of these Short De-
tection circuits are not operational in Stand By mode). I905 is activated by a Low being applied to pin 2, which
forward biases the internal LED. The light from this internal LED is then coupled to the receiver transistor. The
receiver transistor turns On and output a High from pin 3. This high is routed to the base of Q902 turning it On,
which grounds out the Vin at pin (3) of I901, disabling the power supply. Q901 will keep a high on the base of
Q902 as long as there is any voltage available at its Emitter.
The individual Shut Down circuits will be discussed later.
GENERAL INFORMATION:
All of the Power Supply Shutdown circuitry can be broken down into the following category;
•Voltage Missing Detection or Short Detection
•Voltage Too High Detection
•Excessive Current Detection
•Negative Voltage Loss Detection
The following will explain all of these commonly used circuits. The Service Technician should become familiar
with the appearance of these circuit and their function.
VOLTAGE LOSS or SHORT DETECTION
(See Figure 1)
One circuit used is the Voltage Loss Detection cir-
cuit. This is a very simple circuit that detects a loss of
a particular power supply and supplies a Pull-Down
path for the base of a PNP transistor.
This circuit consist of a diode connected by its cath-
ode to a positive B+ power supply. Under normal
conditions, the diode is reversed biases, which keeps
the base of Q1 pulled up, forcing it OFF. However, if
there is a short or excessive load on the B+ line that’s
being monitored, the diode in effect will have a LOW
on its cathode, turning it ON. This will allow a cur-
rent path for the base bias of Q1, which will turn it
ON and generates a Shutdown Signal.
(Continued on page 10)
Any Positive
B+ Supply
B+
Q1
Shut-Down Signal
Voltage
Loss
Detector
Figure 1
PAGE 01-09

DP-2X LOW VOLTAGE POWER SHUT DOWN EXPLANATION
VOLTAGE TOO HIGH DETECTION
(See Figure 2)
Another circuit used is the Voltage Too High Detec-
tion circuit. In the example shown in Figure 2, the
zener diode D1 is connected to a voltage divider. If
the voltage source rises too high, the voltage at the
divider center point will rise as well and trigger or fire
the zener diode which produces a Shutdown signal.
EXCESSIVE CURRENT DETECTION
(See Figure 3)
One very common circuit used in many Hitachi tele-
vision products is the B+ Excessive Current Sensing
circuit. In this circuit is a low ohm resistor in series
with the particular power supply, (labeled B+ in the
drawing). The value of this resistor is determined by
the maximum current allowable within a particular
power supply. In the case of Figure 1, the value is
shown as a 0.47 ohm, however it could be any low
ohm value. When the current demand increases, the
voltage drop across the resistor increases. If the volt-
age drop is sufficient to reduce the voltage on the base
of the transistor, the transistor will conduct, producing
a Shutdown signal that is directed to the appropriate
circuit.
NEGATIVE VOLTAGE LOSS DETECTION
(See Figure 4)
The purpose of the Negative Voltage Loss detection circuit is to
compare the negative voltage with its’ counter part positive volt-
age. If at any time, the negative voltage drops or disappears, the
circuit will produce a Shutdown signal.
In Figure 5, there are two resistors of equal value. One to the
positive voltage, (shown here as +12V) and one to the negative
voltage, (shown here as -12V). At their tie point, (neutral point),
the voltage is effectually zero (0) volts. If however, the negative
voltage is lost due to an excessive load or defective negative
voltage regulator, the neutral point will go positive. This in turn
will cause the zener diode to fire, creating a Shutdown Signal.
SPECIFIC INFORMATION:
In addition, there are 7 Hot Ground side Shutdown inputs that are specifically detected by the main power driver
IC I901. These sensors circuits protect I901 from excessive current, temperature or over voltage.
HOT GROUND SIDE SHUT DOWN SENSING CIRCUITS. (Specific to I901).
LATCHED SHUT DOWN MONITORS: (AC must be removed to recover).
1. (OVP) Pin 3 is monitored for Over Voltage Protection at pin 3 of I901.
2. (TSD) I901 itself is monitored for Excessive Heat. This block is labeled TSD. (Thermal Sensing Device).
3. (OLP) Over Load Protection monitors the difference between the Hot Ground and Floating Ground.
RECOVERING SHUT DOWN INPUT: (Driver IC will recover on it’s own when trouble is removed.)
4. (OCP) Pin 5 monitors the low ohm resistors, R908, R909, and R910. If these resistors have an excessive
(Continued on page 11)
Any Positive
B+ Supply
Voltage Too High
Detector
Shut-Down Signal
Figure 2
Current Sensor
Base
Bias
B+
Shut-Down Signal
R1
0.47
Figure 3
Voltage
Loss
Detector
+12V -12V
Shut-Down Signal
Figure 4
PAGE 01-10

DP-2X LOW VOLTAGE POWER SHUT DOWN EXPLANATION
current condition caused by monitoring the current through the internal Switch MOS FET, the voltage will
rise and pin 5has an internal Over Voltage detection op-amp. If this voltage rises enough to trigger this op-
amp, the IC will stop producing a drive signal.
5. (ABS) Pin 4 also has C915 monitoring spike current in case the CRTs “Snap” indicating a quick discharge
of High Voltage.
6. (BD) Pin 7 Monitors the Run Voltage generated by pin 18 of T901 for excessive voltage.
COLD GROUND SIDE SHUT DOWN SENSING CIRCUITS. (AC must be removed to recover).
(See DP-27 Signal Power Supply (Low Voltage) Shut-Down Circuit Diagram for details)
Looking at Pin 2 of I905 the shut down events are triggered by two routes.
D963, D962:
The cathode of D963 is connected through R982 to pin 10 of PPS3. This in turn is connected to R298 which is
connected directly to the 3.3V power supply produced by IP81 on the Signal PWB. If something were to load
this line down, D963 would forward bias and supply a current path for pin 2 of I905. This in turn would produce
a Shut Down event. See Power Supply Shutdown Photo Coupler I905 Explanation on the previous page.
Q910:
This transistor’s base is connected to Q911 through D955. Q911 emitter is connected to Q912. This transistor is
the Shut down enable circuit.
DP-27 SHUT DOWN CIRCUIT:
There are a total of 3individual Shutdown inputs to the photo coupler I905.
There are a total of 3individual Shutdown inputs to the Relay Inhibit transistor Q903 from the power supply.
There are a total of 4individual Shutdown inputs to the Relay Inhibit transistor Q903 from the Deflection Cir-
cuit. For a total of 10 individual Shutdown inputs that will kill the Lo Voltage Power Supply. (Note: The Hi Volt-
age Power Supply Shutdown will be discussed later.)
All of the Cold Ground side Shutdown detection circuits can be categorized by the two previously described cir-
cuits
In the following explanation, the Shutdown circuits will be grouped. This will assist the Service Technician with
trouble shooting the Chassis, by understanding these circuits and having the associated circuit routs, the techni-
cian can then “Divide and Conquer”.
Voltage Loss Detection through I905 Photo coupler
•Shorted STBY +3.3V generated by IP81 and monitored by (R298) on Signal PWB through PPS3 pin 10
to (D963) on Low Voltage Power Supply PWB. Labeled PROT-SBY on the Schematic.
•Shorted SW+2.2V (IP52 pin 5) on Signal PWB monitored by RP53 through PPS3 pin 11 to to (D961)
on Low Voltage Power Supply PWB. Labeled PROT-SW on the Schematic.
•Shorted SW+3.3V (IP52 pin 2) on Signal PWB monitored by DP53, RP53 through PPS3 pin 11 to to
(D961) on Low Voltage Power Supply PWB. Labeled PROT-SW on the Schematic.
•Shorted SW+5V (IP53 pin 2) on Signal PWB monitored by DP54,RP53 through PPS3 pin 11 to to
(D961) on Low Voltage Power Supply PWB. Labeled PROT-SW on the Schematic.
Q903 Relay Inhibit Activation.
From the Power Supply.
SW +115V Voltage Too High Detection
•Monitored by (D927) See additional Shut Down Circuit Diagram for details.
SW +115V Excessive Current Detection
•Monitored by (Q905) See additional Shut Down Circuit Diagram for details
(Continued on page 12)
PAGE 01-11

DP-2X LOW VOLTAGE POWER SHUT DOWN EXPLANATION
SW –28V Loss Detection
•Monitored by (D937) See additional Shut Down Circuit Diagram for details
From the Deflection Circuit PPD3 connector pin 6.
Vertical B+ 28V Voltage Excessive Current Detection
•Monitored by (Q604) See Deflection Protect Power Supply Shutdown Diagram for details.
Excessive High Voltage Detection
•Monitored by (DH15)See Deflection Protect Power Supply Shutdown Diagram for details.
-5V Loss Detection
•Monitored by (DK90)See Deflection Protect Power Supply Shutdown Diagram for details.
Side Pincushion Failure Detection
•Monitored by (D702,D703)See Deflection Protect Power Supply Shutdown Diagram for details
If any one of these circuits activate the base of Q903 will go High and remove the Power On High from PPS3
connector pin 4 and the power supply will STOP.
SOME SHUTDOWN CIRCUITS ARE DEFEATED IN STANDBY MODE. (Set Off).
As indicated in the Power Supply (Lo Voltage) Shutdown circuit diagram, 3 of the shut down inputs are not ac-
tive when the set is in standby.
•Shorted SW+2.2V (IP52 pin 5) on Signal PWB monitored by RP53 through PPS3 pin 11 to to (D961)
on Low Voltage Power Supply PWB. Labeled PROT-SW on the Schematic.
•Shorted SW+3.3V (IP52 pin 2) on Signal PWB monitored by DP53, RP53 through PPS3 pin 11 to to
(D961) on Low Voltage Power Supply PWB. Labeled PROT-SW on the Schematic.
•Shorted SW+5V (IP53 pin 2) on Signal PWB monitored by DP54,RP53 through PPS3 pin 11 to to
(D961) on Low Voltage Power Supply PWB. Labeled PROT-SW on the Schematic.
These voltage loss sensing 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..
Q911 supplies the high for shutdown if any of the voltage loss circuits become activated. Q911 requires emitter
voltage to operated. Emitter voltage is supplied from the emitter of Q912. Q912s base is connected to the power
on/off line. When the set is not on or turned off, the power on/off line goes Low. This Low pulls the cathode of
D956 low, removing the base voltage of Q912 turning it OFF. This removes the emitter voltage from Q911 and
this circuit can not function. The base of Q912 is also connected to the SW +6V line. This voltage must be active
for this circuit to function.
B+ GENERATION FOR THE LOW VOLTAGE POWER SUPPLY DRIVER IC:
Vcc for the Driver IC is first generated by the AC input. This voltage is called Start Up Voltage. I901 requires
16V DC to operate normal. However, it will begin operation at 6.8V DC on pin (3) of I901.
When AC is applied, AC is routed through the main fuse F901 (a 6 Amp fuse), then through the Line filter L901
to prevent any internal high frequency radiation for radiating back into the AC power line. After passing the fil-
ters it arrives at the main full wave bridge rectifier D901 where it is converted to Raw 150V DC voltage to be
supplied to the power supply switching transformer T901 pin (2).
However, one leg of the AC is routed to a half wave rectifier D904 where it is rectified, routed through R906 and
R907 (both a 68K ohm resistor), filtered by C911, clamped by a 30V Zener D907 and made available to pin (3)
of I901 as start up voltage. When this voltage reaches 6.8Vdc, the internal Regulator of I901 is turned On and
begins the operation of I901.
When the power supply begins to operate by turning on and off the internal Switch MOS FET, the Raw 150V DC
routed through T901, in on pin 1(Drain) and out on pin 2which is the Source. The Source of the internal Switch
MOS FET is routed out of pin (2) through three low ohm resistors to hot ground. When the internal Switch MOS
FET turns on, it causes the transformer to saturate building up the magnet field. When the internal Switch MOS
FET turns off, the magnet field collapses and the EMF is coupled over to the secondary windings, as well as the
drive windings. The drive windings at pin (8) produce a run voltage pulse which is rectified by D905, filtered by
C911 then routed clamped by D907 and now becomes run voltage (16V) for I901 pin 3.
PAGE 01-12