Datasheet ITC 222 Datasheet

VERTICAL

TO
E8

RED BIAS

<21-B>

TO
E7

GRN BIAS

E5003

E5007

TP50

RED OUTPUT

TP24

194V

TECHNICAL TRAINING

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ITC222

PTV Troubleshooting Guide

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FOREWORD

This publication is intended to aid the technician in servicing the ITC222 television chassis.
Directed at the safety circuitry and based on the previous ATC221 Safety Circuit
Troubleshooting Manual, it will explain the theory of operation of those circuits highlighting
new and different technologies associated with this digitally controlled chassis. It is
designed to assist the technician to become more familiar with the safety circuit operation,
increase confidence and improve overall efficiency in servicing the product.

Note: This publication is intended to be used only as a training aid. It is not meant to replace
service data. Thomson Service Data for these instruments contains specific information
about parts, safety and alignment procedures and must be consulted before performing
any service. The information in this manual is as accurate as possible at the time of
publication. Circuit designs and drawings are subject to change without notice.

SAFETY INFORMATION CAUTION

Safety information is contained in the appropriate Thomson Service Data. All product
safety requirements must be complied with prior to returning the instrument to the
consumer. Servicers who defeat safety features or fail to perform safety checks may be
liable for any resulting damages and may expose themselves and others to possible injury.

All integrated circuits, all surface mounted devices, and many other
semiconductors are electrostatically sensitive and therefore require
special handling techniques.

First Edition - First Printing
Copyright 2005 Thomson, Inc.
Trademark(s)® Registered Marca(s) Registrada(s)
RCA and the RCA logos are trademarks of THOMSON
S.A. used under license to TTE Corporation
Printed in U.S.A.

Prepared by
Thomson, Inc for TTE Technology, Inc.
Technical Training Department, INH905
PO Box 1976
Indianapolis, Indiana 46206 U.S.A.

Contents

Foreword............................................................................................................................. 3

Safety Information CAUTION............................................................................................. 3

Introduction ........................................................................................................................ 5

Overview ............................................................................................................................. 7

ITC222 Dead Set Troubleshooting.................................................................................. 10

Shutdown or Three Strikes.............................................................................................. 12

Standby Power Supply Troubleshooting........................................................................ 1 3

System Control (SSB) Troubleshooting......................................................................... 14

Safety Shutdown .............................................................................................................. 15

ITC222 Force ON RUN supply ......................................................................................... 16

Run Supply Troubleshooting .......................................................................................... 17

Run Supply Troubleshooting Continued........................................................................ 18

Deflection Shutdown........................................................................................................ 19

ITC222 Force on Horizontal Drive................................................................................... 20

Deflection Shutdown 2..................................................................................................... 22

Beam Info T roubleshooting............................................................................................. 23

EW Troubleshooting ........................................................................................................ 24

XRP T roubleshooting....................................................................................................... 25

V ertical Troubleshooting ................................................................................................. 26

Start-up and Shutdown Information

Power On/Off............................................................................................................... 27

Audio Protection ......................................................................................................... 29

Audio Power Supply Shutdown................................................................................. 29

Audio Output Safety Shutdown (SAFETY_AP)......................................................... 30

Over Voltage Protection ............................................................................................. 31

Power Supply Voltage Loss-Safety PTV CRT ........................................................... 32

Safety_PTV Interlock .................................................................................................. 34

Safety_PTV_CRT (Rear Projection Only) .................................................................. 35

Deflection Shutdown Overview ................................................................................. 37

Excessive High Voltage .............................................................................................. 38

ABL & XRP................................................................................................................... 39

Safety Enable .............................................................................................................. 39

Vertical Guard ............................................................................................................. 40

SSC_VERTICAL_GUARD............................................................................................ 40

East-West Protect ....................................................................................................... 42

Summary ........................................................................................................................... 43

Appendix

SSB Component and Test Point Locations

Interconnect Wiring Diagram

Op-Amps

ITC222 Safety Shutdown

4

Introduction

The ITC222 Troubleshooting Guide will cover the different shutdown circuits and how to

troubleshoot each. It will concentrate on each circuit individually but provide an overall starting

point to isolate each shutdown when possible.

Also included in this manual is detailed information about each shutdown. Flow charts and

procedures are used to isolate down to a circuit and, where possible, components. Some of

the procedures require disabling a shutdown and potently create a safety issue if not performed

correctly. It is the responsibility of the servicing technician to return the set back to safe

operation.

An Appendix provides additional information on test points and Op-Amp operation.

This training material assumes the reader has a base knowledge of the ITC222 television

chassis. The material has been prepared using general values of components. These

components and other circuitry may change over time, so in all cases, Electronic Service

Data for the instrument should be consulted for the most accurate component values and

voltages.

Typical nomenclature for component ID and references to ground and supply voltages

will be used throughout. To designate individual pin assignments of an IC and active

components the following formats are used.

IR001-115 designates IC IR001, pin 115.

TR198-B designates the Base of transistor TR198.

Power supply labels will be used whenever possible. S for standby operation and R for

run. Normal operating voltages and signal designations will be used. For example:

SAFETY ENABLE would stand for a signal that under normal run conditions would be a logic

HIGH, in most cases near +5V . SAFETY ENABLE would signify a signal whose normal operating

level is LOW, in most cases near ground.

EEPROM’s or Electrically Erasable Programmable Read Only Memory, are sometimes

referred to as NVM’s or NonVolatile Memory devices. They are the same device simply

called by different names.

The following symbol is used to reference additional information. It has the page number were

the additional information can be found.

INFO

Pg XX

ITC222 Safety Shutdown

5

5

FP400

CP410

CP411

DP400

LP401

LP400

MID

BP400

BP401

BP414

TP630

BP610

IP650

LP650

LP605

BL600

BH

BL660

BW004

BV

Watchdog

Circuit Area

CPS

2
0
4
P
B

BP010

BP130

BP120

TL010

BL200

BP011

LP050

LL008

PSD

BP150

BL035

BF001

TP020

BL500

IP080

LP020

BP005

BL111

BP501

BP500

BV001

Link

G

BK202

IR & Key Board

BR001

IR001

Gem Cam

IT600

DVI

BV500

IV400

IR006

IX400

Comp

DVI

1

Aud

GH GV RH RV

BW005

IK201

IV100

CVBS

1&2

SSB

IC040

Comp

BK270

IV300

IX300

S

2

Vid

CAM

BA002

r
e
n
u
T

n

i
a
M

s
s
u
B
I

C
E
T

BA010

r
e
n
u
T

d
n
o
c
e
S

Monitor

BW001 BW002

BA001

IA001

Out

IA900

IB101

R-CRT

IB201

Grn

IB301

Blue

Red

BB104

BB204

BB201

BB203

BB202

G-CRT

BB303

B-CRT

Figure 1; CBA Layout

The ITC222 PCB’s may be referenced during troubleshooting. The Board layout view above
will be used to navigate to the various test points referred to in this troubleshooting guide.
The view is from the top of the PCB with reference connectors shown for ease of identifica­tion. The technician may count from pin one from either the top or bottom of the board. In
most cases the test points are easier to access from the bottom of the board.
Some connectors may appear in-line from the top, but may have staggered pinouts on the
solder side as in the figure below.

Pin 1 Pin 1

15 Pin Connector Top View

6810

123

4

5

7 9 11 13 15

12 14

15 Pin Connector Bottom View

Figure 2; Connector Pinouts

Note from the top of the board, pin one through pin fifteen is sequential. However, from the
bottom of the board the pins are staggered with pin one starting from the larger row at the
lower left, pin 2 diagonally up, then diagonally back to pin 3 and so on.

ITC222 Safety Shutdown

6

Overview

As the ATC221 did previously, the ITC222 uses two independent legs of safety and

operational shutdown circuits closely tied together. These legs are made up of other

circuits that protect individual sections to prevent catastrophic failure in circuits such as

the power supplies, deflection, convergence and others. The individual sections are

connected to one of two main branches of protection circuitry: one for safety related

shutdowns of the main run supply (Safety Shutdown) and another for deflection related

failure shutdown including XRP Deflection Shutdown).

The two branches operate independently of each other and although performing different

functions both result in a shutdown of the set which may or may not provide error code

data. In many cases recovering from shutdown is automatic. Other times an AC recycle

of the instrument is required. If there are three deflection rest arts within 2 minutes a special

warm start is performed. After the third deflection restart the system will switch to Standby-

mode and stay there for a minimum of one minute. During this minute all FPA and remote

IR commands are ignored which means the set cannot be turned on. This is implemented

due to safety reasons and to avoid overheating components.

ITC222

Shutdown/Safety

SAFETY_AP

Block Outline

SAFETY_INT

TO MAIN MICRO

BEAM CURRENT

PS LOSS

SAFETY_PTV_CRT

STARTUP DELAY

PS OVERVOLTAGE

Conv Micro

SAFETY

IP190B

5

+

-

6

NORMAL: High
PROTECT: Lo
STDBY: Lo

IP190A

2

IV400

VID PROC

EHTIN

IK201

SSC

V GUARD

RUN:< +3V
XRP: > +3.8V

4

28

+5Vs

TP210

XRP

EW_PROT

BEAM INFO

SAFETY_ENABLE

VERTICAL GUARD

Safety Shutdown

To Pwr On Switch
NORMAL: Low
PROTECT: High

Figure 3; Shutdown / Safety Block

7

Deflection Shutdown

ITC222 Safety Shutdown

In many areas multiple signal lines converge into one point. Most times those converging
lines are isolated by a diode. New for the ITC222 is the use of open collector comparators
allowing direct connection of multiple signal lines. Since one shutdown can affect other
safety or protection lines it complicates troubleshooting. This manual will attempt to show
where common checkpoints and measurement locations are along with nominal voltages
expected during run or shutdown situations.

Below are the shutdown circuits and the signal lines that connect to the different shutdowns.
The Safety shutdown may be broken into five distinct sections:

• Audio Power Supply and Audio Output Monitoring

• Main Run Power Supply Loss (PS LOSS)

• Rear Projection Instrument Safety (CRT Scan Loss protection)

• Start-up Delay

• Power Supply Overvoltage

Deflection Shutdown may also be broken into six distinct sections:

• Beam Current monitoring

• XRP

• East West Circuitry Power Dissipation

• General Deflection Safety

• Micro based suspension of the Safety Monitoring during deflection start-up
(Safety_Enable)

• Vertical Guard to shut down CRT drive in the event of vertical scan failure

Because many of the sensors are looking at voltages that could cause shutdown circuits
to activate, there are typically threshold voltages causing the actual shutdown trip. In this
manual many voltages provided are “nominal”. In other words, the voltages may change
during operation or may not be exactly as indicated depending upon circuit tolerances,
alignments, and adjustments. When nominal voltages are indicated study the surrounding
circuits to determine how close to the nominal the voltage should be. Every attempt will
be made to provide the range expected, however; due to accumulative circuit tolerances
nominal voltages are interdependent on the circuits feeding them and may vary over a
wide range yet still be valid. The most important indication of circuit activity will usually be
the relationship of the input voltages of the Op-Amps or comparators and whether the
output of those devices logically follow the inputs.

Threshold voltages are generally more accurate since they have been set specifically to
shutdown operation if the threshold is reached. The only exception to the specific threshold
voltage is XRP, which must be adjusted according to specific circuit reaction to many
interrelated conditions.

ITC222 Safety Shutdown

8

SAFETY_AP

PS LOSS

ITC222

Shutdown/Safety

Block Outline

SAFETY_INT

TO MAIN MICRO

IV400

VID PROC

RUN:< +3V
XRP: > +3.8V

4

EHTIN

BEAM CURRENT

XRP

SAFETY_PTV_CRT

ST AR TUP DELAY

PS OVERVOLTAGE

Safety Shutdown

IK201

Conv Micro

28

SSC

V GUARD

SAFETY

IP190B

5

+

-

6

NORMAL: High
PROTECT: Lo
STDBY: Lo

+5Vs

TP210

IP190A

2

To Pwr On Switch
NORMAL: Low
PROTECT: High

Figure 4; Shutdown / Safety Block

EW_PROT

BEAM INFO

SAFETY_ENABLE

VERTICAL GUARD

Deflection Shutdown

Tool Box Key

The graphic below is a key to the ICONS found in the troubleshooting procedures. It lists the
tools and test equipment required to perform each procedure.

TOOL BOX

Equipment required for this procedure

Digital Volt Ohm Meter

Oscilloscope

Isolation Transformer

Variable
ISO-Tap

AC Voltage Out
with 120VA C In

Monitor

ADD

Basic Hand Tools

Signal Generator

ATSC/NTSC

Chipper Check

Figure 5; Tool Box Key

ITC222 Safety Shutdown

9

ITC222 Dead Set Troubleshooting

The first step in all troubleshooting is to determine what is or is not working. The following
information should be used when the set is totally dead or nothing happens when the power
button is pushed.

1 Once the main fuse has been eliminated as a potential problem, measure the +1.8Vs

supply at IP551 on the SSB board:

Figure 6; STBY 1.8V Location

The +1.8Vs voltage is the main supply for the main microprocessor, IR001. Without it,
nothing will fire up. If missing, troubleshoot the Standby Power Supply.

2 Once the +1.8Vs supply has been confirmed as operational, check the clock (pin 6)

and data (pin 5) lines to the main NVM, IR005.

ITC222 Safety Shutdown

Figure 7; Clock and Data Location

10

In the first 100mS after AC power is applied the CLOCK and DATA lines must rise to very
near +5V and have at least few cycles of data. This indicates communication between the
main microprocessor and NVM (EEPROM). Note only a limited amount of Data is
transferred when AC is applied. Communications will cease until the power ON button is
pressed to start the chassis. However, the short amount of data transfer between the
microprocessor and NVM is a good indication that communications between the main
microprocessor, ROM and RAM were successful and the main microprocessor is alive.

From observing clock and data activity, there are two failure indications. First, if there were
no signs of data or clock suspect the main microprocessor is defective. However if there
is constant communications it indicates the microprocessor is trying to communicate with
the NVM and cannot. Suspect a defective NVM (EEPROM). In either case the SSB should
be replaced.

NOTE: In some cases it may be required to check the communications again. To do so
requires the main micro be in a zero voltage state. Be aware the mains doubler can hold
a significant voltage for a long period of time. AC must be removed for at least several
minutes to give the +1.8Vs supply time to completely bleed off. To save time the +1.8Vs
supply may be bled by shorting CP555 on the SSB module. Check the +1.8Vs supply to
make certain it is less than +0.2V before attempting to reapply AC power.

Figure 8; Location of Reset Cap

POWER FAIL (INF_POW_FAIL)

Figure 9; Inf_Pow_Fail

Another useful preliminary check is the INF_POW_FAIL voltage located on the PSD board.
The voltage monitors an unregulated rectified output from the +7Vs winding. This can be
located on one end of RP231 as shown. During normal operation this voltage will be less
than -1V and normally stays around -2V. INF_POW_FAIL can indicate severe loading
problems on the standby supplies. Absence of a negative INF_POW_FAIL signal will not
allow the chassis to start.

ITC222 Safety Shutdown

11

Troubleshooting flow charts and procedures

Start

Apply AC power

and Press the

power switch

Does the FPA

LED flash?

Yes

System

Reset

See Bottom of Page

for System Reset

No

Check standby

power supply

voltages per chart

Voltages
correct?

Shutdown or Three Strikes

TOOL BOX

Equipment required for this procedure

Device Voltage

DP220-C +7.2V

IP250-3 +4.99V

DP240-C +3.4V

Troubleshoot the

NoYes

Standby power

supply

INFO

Pg 13

Monitor the PO (Power

ON) line at DP211-A and

press the power switch

Did the PO line

change state (go from

low to high)?

Yes

System

Reset

System Control is trying to

turn on the run supply.

Monitor the Safety shutdown

at TP210-C and press the

power switch.

See Bottom of Page

Location INFO

No

for System Reset

Troubleshoot

System control

INFO

Pg 14

Does TP210-C go

high (Protect)

Yes

Troubleshoot Safety

Shutdown

No

Troubleshoot

Deflection
Shutdown

INFO

System Reset: Remove AC
power and short out CP555 for 10
seconds then reapply AC power.
See page 11 for details.

Pg 19

ITC222 Safety Shutdown

12

Troubleshooting flow charts and procedures

Standby Power Supply Trouble­shooting

Start

TOOL BOX

Equipment required for this procedure

Check for raw B+

at connector

BP010 between

pins 2 and 3.

B+ correct

(+306Vdc)?

Yes

Check pin 2 of

IP020 for +10Vdc.

Voltage Correct?

Yes

Check Standby
supplies again?

Are the Standby

Supplies pulsing?

No

Suspect AC Input /

Mains Input Supply

No

No

Suspect IP020, DP023,

RP023 and RP028.

Standby Supply is

working, Check +5V

regulator IP250 pin 3

for 5V.

Yes

Check pin 1

of IP030.

Pin 1 of IP030

+4.98V?

Yes

Suspect TP026,

IP030, and IP020

No

Voltage Correct? Suspect IP250

Yes

Standby Supply

is working.

Suspect DP240,

IP240, IP030

No

13

ITC222 Safety Shutdown

Troubleshooting flow charts and procedures

See Bottom of Page

for System Reset

Check pin 6 and 5 of IR005
with in the first 100ms after

Start

Apply AC power

and Press the

power switch

Does the FPA

LED flash?

Yes

System

Reset

for Clock and Data activity

AC power is applied

No

System Control (SSB) Trouble­shooting

Device Voltage

Check standby

power supply

voltages per chart

Voltages

correct?

DP220-C +7.2V

IP250-3 +4.99V

DP240-C +3.4V

NoYes

Troubleshoot the

Standby power

supply

INFO

Pg 13

Replace SSB No Activity

See Bottom of Page

for System Reset

Clk and Data

activity?

Few cycles then nothing

Check connections

between SSB and PSD

(BV001 and BP500)

System

Reset

Monitor pin 18 of
BP500 and press
the power switch

Does pin 18 go

high? (PO)

Yes

Suspect connection problem

with BP005 or on the PSD

(Power on line)

Replace SSBContinuous Activity

TOOL BOX

Equipment required for this procedure

Variable

ISO-Tap

Monitor

ADD

AC Voltage Out
with 120VAC In

Replace SSBNo

System Reset: Remove AC
power and short out CP555 for 10
seconds then reapply AC power.
See page 11 for details.

ITC222 Safety Shutdown

14

Troubleshooting flow charts and procedures

Safety Shutdown

Safety Shutdown Start

TOOL BOX

Equipment required for this procedure

Disconnect BA010 to
disable SAFETY_AP

and press the power

switch.

Does the set start and

run with no audio?

No

System

Reset

Disconnect BV500 from SSB
and jumper pins 1 and 16 on

BV500 and press the power

switch.

Does the set

start and run?

No

Remove AC power and check RUN supplies

for excessive loads or shorts. Use the chart

found on page 16 as reference for what

supplies to check.

See Bottom of Page

for System Reset

Yes

Yes

Location INFO

Troubleshoot Audio

Output Circuit

Troubleshoot PTV

Interlock Circuit.

INFO

Pg 38

Resistance
checks ok?

No

Troubleshoot Circuit

where resistance was not

correct.

Yes

See Force on RUN

supply.

15

INFO

Pg 16

System Reset: Remove AC
power and short out CP555 for 10
seconds then reapply AC power.
See page 11 for details.

ITC222 Safety Shutdown

Troubleshooting flow charts and procedures

TOOL BOX

Equipment required for this procedure

ITC222 Force ON RUN supply

1. Unsolder collector of TL010 (Horizontal Output)

2. Short base to emitter of TP210

3. Short emitter to collector of TP150

4. Apply AC power

Note: Without horizontal drive (H_DRIVE), regulation is disabled. The +137Vr will vary
from +140V to +160V. This is considered normal operation for the Run Supply when forced
to operate without Horizontal feedback.

5. With the run power supply forced on, check the following voltages per the chart
below. If all voltages are ok, suspect system control or power ON problem. If one or
more voltages are incorrect or all are missing, troubleshoot the missing or incorrect
voltage from the run supply.

Safety Shutdown Device Resist ance to GND

Sense_3V3 IC 001-2 .5K
Sense_2V5 IC 006-2 .4K

Device Voltage

DP110-C +142.5V
DP130-C +15.9V
DP135-A -15.7V

+3V3 IP 530-2 .57K

+5V TP520-S 160 Ohms
+8V IP 510-3 1.5K
+9V IP 540-3 1.2K

USYS DP 110-C 27K

DP120-C +20.5V
DP140-C +11.0V
DP150-C +6.2V

IP540-3 +9.0V
IP510-3 +7.9V

TP520-S +5.1V

20V DP120-C 3K
10V DP140-C 1.3M

6V DP150-C 1.2M

IP530-2 +3.2V
IP531-2 +1.8V

Figure 10; Resistance Chart

ITC222 Safety Shutdown

Figure 11; VoltageChart

16

Troubleshooting flow charts and procedures

Run Supply Troublehsooting

Start

TOOL BOX

Equipment required for this procedure

With the Run

Supply forced on,

apply AC power

Check pin 3 of

IP170 for

waveform.

Waveform

correct?

Yes

Check pin 7 of

IP170 for PWM

pulse.

Waveform

correct?

Yes

Check for PWM

pulse at Collector

of TP160.

Waveform

correct?

Yes

No

No

Suspect OSC

No

Circuit IP170 and

Suspect PWM Circuit

IP170, TP179, and

Suspect TP160, TP161,

TP210, IP190 Circuit.

TP170

CP170

Check for PWM
pulse at pin 5 of

IP050.

Waveform

correct?

Flow Chart 2

Run Power Supply

Suspect LP070No

INFO

Pg 18

ITC222 Safety Shutdown

17

Troubleshooting flow charts and procedures

Run Supply Troublehsooting Con­tinued

Flow Chart 2 Run Power

Supply Start

Check for PWM at

pin 7 of IP050.

TOOL BOX

Equipment required for this procedure

Waveform

correct?

Yes

Check pin 1 of

IP050 for PWM

pulse.

Waveform

correct?

Yes

Check for PWM

pulse at emitter of

TP050, 051.

Waveform

correct?

No

No

No

Check Vcc to IP050,

Check TP034

Suspect TP080,

TP081 Circuit

Suspect TP050, TP051,

and CP056.

ITC222 Safety Shutdown

Yes

Check for PWM

pulse at the

gate of TP020.

Waveform

correct?

Yes

Suspect TP020,

LP050

Suspect DP053No

18

Troubleshooting flow charts and procedures

Suspect HV

Splitter or the

CRT(s).

Stays up

Deflection

Shutdown Start

Disconnect anode lead from HV

splitter. Connect HV probe and

monitor High Voltage. Apply AC

power and Press the power

switch.

What happens

with High

Voltage?

Shutsdown

System

Reset

Short B-E of

TV852 and press

the power switch

See Bottom of Page

for System Reset

Deflection Shutdown

Equipment required for this procedure

No HV

See force on

Horizontal Drive

TOOL BOX

INFO

Pg 20

Does high

voltage come up

and stay?

Yes

System

Reset

Leave TV852 shorted and

monitor pin 1 of IV821.

Press the power switch.

Does the voltage

go above .18V?

Yes

XRP being tripped

No

See Bottom of Page

for System Reset

No

INFO

See Deflection

Troubleshoot Beam

Protect or EW Protect

Pg 25

Shutdown 2

INFO

INFO

Pg 22

Pg 23-24

System Reset: Remove AC
power and short out CP555 for 10
seconds then reapply AC power.
See page 11 for details.

19

ITC222 Safety Shutdown

Troubleshooting flow charts and procedures

ITC222 Force on Horizontal Drive

This procedure will verify if the SSB is generating horizontal drive or not. If drive is present
from the SSB, then see Deflection Shutdown 2 Troubleshooting, if not suspect the SSB as
the problem.

1. Remove ribbon cable BL111 to BV001

2. Jumper pins 1 and 21 on BL111 PSD CBA

3. Add 1K resistor to ground (Cold) from pin 17 of BV001

4. Monitor waveform at pin 8 of IV400 or DC voltage. Voltage or waveform will remain
for about 1.5 seconds when power is pushed.

DC reading on pin 8 of IV400:

4Vdc = no drive
2Vdc = drive

PSD CBA SSB CBA

BL111

BV001

21

17

1

Figure 12; Force On H-Drive

1K

TOOL BOX

Equipment required for this procedure

ITC222 Safety Shutdown

20

Variable
ISO-Tap

AC Voltage Out
with 120VA C In

Monitor

ADD

Troubleshooting flow charts and procedures

Figure 12a; Force On H-Drive

H_DRIVE when forced on

Figure 12b; Force On H-Drive Waveform

21

ITC222 Safety Shutdown

Troubleshooting flow charts and procedures

Deflection Shutdown 2

TOOL BOX

Equipment required for this procedure

Deflection 2

Shutdown Start

Disconnect TL029-D (EW

Buffer). Apply AC power and

Press the power switch.

Does set stay on

Shutsdown

System

Reset

Monitor pin 1 of IV821.

Press the power switch.

Does the voltage

go above .18V?

Yes

Stay on

See Bottom of Page

for System Reset

No

EW Protect active

suspect problem in EW

Suspect a problem in the

Circuit

Beam Info Circuit

INFO

INFO

Pg 24

Pg 23

ITC222 Safety Shutdown

XRP being tripped.

See XRP

Troubleshooting

22

INFO

Pg 25

System Reset: Remove AC
power and short out CP555 for 10
seconds then reapply AC power.
See page 11 for details.

Troubleshooting flow charts and procedures

Beam Info Troubleshooting

TOOL BOX

Equipment required for this procedure

Beam Info Start

Disable shutdown by

shorting base to emitter of

TV852.

Measure the voltage

at pin 13 of BL111.

INFO

Pg 42

Voltage low?

Yes

Remove anode lead
form HV splitter and
recheck the voltage
on pin 13 of BL111.

Voltage low?

Yes

Suspect TL311, 312 and

precision resistors off of pin 10

of LL008. Also check DL302,

303, and 301

No

Suspect IV820, DV822

No

and associated Circuit.

Suspect HV splitter,

CRT(s), LL008

23

ITC222 Safety Shutdown

Troubleshooting flow charts and procedures

EW Troubleshooting

TOOL BOX

Equipment required for this procedure

EW Start

Disconnect Drain of TL029

EW Buffer and press the

power switch.

Measure the DC on TL120-C.

The voltage should read about

+48V.

INFO

Pg 40

Drive circuit is ok suspect

TL029, RL021, 025, 024,

023, DL028, 029.

Equal to

Is the voltage

more, less, or

equal to +48V?

Less

Yoke

More

Suspect CL031, 032,

035, DL032, 030.

ITC222 Safety Shutdown

24

Troubleshooting flow charts and procedures

XRP Troubleshooting

TOOL BOX

XRP Start

Remove anode lead from

HV splitter.

Disable XRP by shorting base

to emitter of TV852.

Monitor the DC voltage at the

collector of TL010 and press the

power switch.

Equipment required for this procedure

INFO

Pg 42

Suspect IV821 and it’s

associated components.

Voltage < +150Vdc?

Yes

Measure the wave

form at TL010-C.

Waveform

Correct?

Yes

Measure the DC

voltage on pin 10

of BL111.

Equal to Suspect RL045, 303,More

Voltage more,

less, or equal to

+26VDC?

No

No

039, DL030, 032, and

Run regulation

problem

Suspect CL031, 038,

LL008

Less

RL043, DL043, and

CL043

25

ITC222 Safety Shutdown

Troubleshooting flow charts and procedures

Vertical Troubleshooting

Vertical

Troubleshooting

Start

Disconnect anode lead from HV

splitter. Apply AC power and

Press the power switch.

Measure the +13Vr

and the -13Vr.

Are these voltages

correct?

Yes

Measure

waveform on

IF001 pins 1 and 7

Suspect IF001, DL251,

No

DL221, F251, 221.

TOOL BOX

Equipment required for this procedure

INFO

Pg 44

Waveforms

correct?

Yes

Measure

wavefrom on

IF001 pin 3.

Waveform

correct?

Yes

Suspect Yoke(s) or
yoke return Circuit.

No

No

Check drive circuit

back to IV400

Suspect IF001, RF020,

DF033, RF009.

ITC222 Safety Shutdown

26

Startup and Shutdown Informataion

IR001

Main

MICRO

RUN:Lo
STDBY:Hi

+5Vs +5Vs

87

RR198

10K

RR199

100

SSB BOARD

RP571

47K

PO

PO_TR

TR198

PWR ON

Part of
BP500

MAIN POWER START UP/SHUTDOWN

Part of
BP005

PSD BOARD

1818

RUN: +4.4V
STDBY: +0.4V

PO1

RP199

22K

Run: +3V

Stby: 0.3V

RP189

1K

RP200

CP199

47K

47uF

SLOW START

DP200

+

Run: +3.8V

Stdby: +2.8V

RP196

DP211

RP193

470

22K

+5Vs

To

SAFETY

RP190

18K

5

6

IP190B

+

-

7

RP213

10K

RP210

2200

0V

Nominal

RP212

10K

RUN: +4.8V
STDBY: +1.0
SHUTDOWN: 0V

+5Vs

LP050-22

36VAC

RP163

82K

RP162

10K

RUN: 0V
STDBY: +4.4V
SHUTDOWN: >+2V

TP210

POWER ON

RUN: +0.25V
SHUTDOWN: 0V

TP161

POWER ON

Figure 13; Power On / Off

POWER ON/OFF

The ITC222 start-up sequence and circuitry varies little from the ATC221. The start-up
circuits are also the same circuitry that shut the chassis down during any Safety Shutdown
event. The PO (Power On) signal starts the run supplies.

The basic start-up active component circuit consists of IR001-87 (the main micro), TR198,
DP211, TP210, and TP161. When in standby mode, IR001-87 is HI turning on TR198
grounding the cathode of DP211. That turns on TP210 which turns on TP161 grounding
the main power supply PWM waveform and holding the main run supplies off. (See other
training material for the complete operation of the run supply.)

When a remote control IR or Front Panel Key press initiates the Power On sequence,
TR198 turns OFF allowing the PO/PO1 line to go high. That would normally instantly turn
the PO Switch TP210 OFF allowing the main PWM supply to operation. However as soon
as TP198 turns OFF, CP199 begins charging through a divider consisting of RP189, RP199,
RP571, and the +5Vs supply. When the cathode of DP211 reaches about +4.2V it turns
OFF. With DP211 OFF, TP210-B is biased OFF by the divider network of RP213, RP210
and the +5Vs supply which places about +4.8V on TP210-B. When TP210 turns OFF the
run supplies start. The cathode of DP21 1 eventually reaches about +4.4V and it continues
to decuple the main start-up/shutdown switch TR198, allowing safety protection from
IP190B. The time delay to start the main supplies is 2-5 seconds depending upon
component tolerances.

To shut the run supplies off, IR001-87 again initiates the command this time by going HI.
That turns ON TR198 which turns ON DP211. That turns on TP210 shutting down the
main run supplies. CP199 maintains a residual charge for a period of time, discharging
through a divider consisting of RP189, DP200, RR199, and TR198. If a false start occurs

27

ITC222 Safety Shutdown

IR001

Main

MICRO

RUN:Lo
STDBY:Hi

+5Vs +5Vs

87

RR198

10K

RR199

100

SSB BOARD

RP571

47K

PO

PO_TR

TR198

PWR ON

Part of
BP500

MAIN POWER START UP/SHUTDOWN

Part of
BP005

PSD BOARD

1818

RUN: +4.4V
STDBY: +0.4V

PO1

RP199

22K

Run: +3V

Stby: 0.3V

RP189

1K

RP200

CP199

47K

47uF

SLOW START

DP200

+

Run: +3.8V

Stdby: +2.8V

RP193

RP196

DP211

470

22K

+5Vs

To

SAFETY

Figure 13a; Power On / Off

RP190

18K

5

6

IP190B

+

-

7

RP213

10K

RP210

2200

0V

Nominal

RP212

10K

RUN: +4.8V
SHUTDOWN: 0V

+5Vs

LP050-22

36VAC

RP163

82K

RP162

10K

RUN: 0V
SHUTDOWN: >+2V

TP210

POWER ON

RUN: +0.25V
SHUTDOWN: 0V

TP161

POWER ON

and CP199 has greater than +0.8V, the Run supplies will continue shutting down.
The voltage on CP199 is the same on IP190B-6, the inverting input of the IC. When the

run supplies shut down, the non-inverting input IP190B-5 immediately goes to +0.8V by a
network consisting of RP190, RP192, DP193, and RP196. As long as the inverting pin is
greater than the non-inverting pin, the output of IP190B-7 will remain low. Only when
CP199 is less than approximately +0.8V can TR198 take control of a new start-up
sequence.

During any safety related event, the SAFETY line connected to IP190B-5, the non-inverting
input will be drawn low. When it slips under the normal run voltage on IP190B-6 (~ +3V)
the output goes toward the negative supply, in this case ground. With TP210-B now low,
it turns on turning on TP161 and shutting down the main PWM supply.

The PO signal itself can be a good indication of whether start-up problems are caused by
a direct shutdown from the micro or safety shutdown. The PO signal from the micro will
follow typical logic switching characteristics, either being high (+5V) or low (0V). Note the
safety shutdown circuitry does not control this line directly! The quiescent voltages in the
circuit will cause IP190B-6 to reach a nominal run voltage of around +3V. During standby
the output of IP190B on pin 7 will normally be around +1V. But during a shutdown event
triggered by IP190 the IC is slammed towards the negative rail (in this case ground)
providing good indication the chassis is in shutdown from the protection circuits rather
than in standby.

ITC222 Safety Shutdown

28

0V

Nominal

SAFETY_AP

SSB Board

L Spk

R Spk

Out

RA250

RA251

100K

100K

RA263

8.2K

Out

RA252

100K

RP197

22K

RP198

10K

+UA

+15Vr

-15Vr

RA253

100K

RA261

100

TP197

RA256

470

RA255

47K

RA254

47K

DP197

+5Vr

Audio PS & Overvoltage Protection

(All components on PSD Board

except as noted)

+7.0V

Nominal

RP195

1200

Run: +5V
Safety: 0V

DP193

RP194

1K

RA259

10K

TA252

Run: 0V
Safety: +5V

RA257

390K

RA260

100

RA262

100

RA258

100K

TA251TA250

RP192

100

DA250

20

20

RP193

470

Run: +5V
Safety: 0

TA253

Part of
BP005

Part of
BP500

RP190

10K

From
Slow
Start

+5Vs

RP196

22K

+3.8V

Nominal

IP190B

5

+

-

6

RUN: +4.8V
SHUTDOWN: 0V

+3.0V

Nominal

+4.8V

Nominal

RUN: +4.8V
SHUTDOWN:0V

RP213

2200

7

OVER VOLTAGE

PROTECTION

0V

Nominal

RP212

10K

TP210

POWER ON

RP201

3300

1

IP190A

LP050-22

RUN: 0V
Stdby: +4.4V
SHUTDOWN: >+2V

+

-

36VAC

3

2

RP163

82K

RP162

10K

+6Vr+5Vs

RP202

10K

RP204

4.75K

RUN: +0.25V
SHUTDOWN: 0V

TP161

POWER ON

RP203

2.43K

+4V

Nominal

-UA

+5Vs

Figure 14; Audio Protection

AUDIO PROTECTION

New to the ITC222 is a monitor circuit on the audio power output device, IA002. That
makes two independent circuits monitoring either the audio power supply or the audio
outputs.

AUDIO POWER SUPPLY SHUTDOWN

The audio power supplies are monitored directly by TP197. When the chassis is running,
the nominal voltage is +17V on the ends of a resistor divider network consisting of RP197/

98. With both voltages at nominal values, TP197-B is about -0.6V and the transistor is

OFF.
The positive supply is monitored by voltage divider RP194/95 placing about +7.0V at the

cathode of DP193. The Safety Line connected to IP190B-5 normally runs at a nominal
+3.8V so DP193 is reversed bias. If the positive supply is reduced or fails, DP193 becomes
forward biased by the +5Vs supply. That causes the non-inverting input of IP190B-5 to
go lower than the inverting input (pin 6, approximately +3.0V) and the output on pin 7 will
go low. When that line is pulled low, the safety circuit trips (previously described) and
shuts down the main power supply. This is the same protection mechanism in the event
both audio rails begin to dip. Even though the bias on TP197-B may remain at -0.6V, at
some point the positive rail will dip far enough to trip DP193 and a shutdown will occur.

If the negative supply is drawn down or disappears, TP197-B is forward biased by the
remaining positive audio supply turning it on. When TP197 turns on, DP193 is forward
biased causing the same results as loss of the positive supply.

ITC222 Safety Shutdown

29

AUDIO OUTPUT SAFETY SHUTDOWN (SAFETY_AP)

The audio output safety shutdown consists of four discrete transistors that monitor the
voltage on the audio IC output lines, IA002-2 and IA002-4. The transistor network, when
tripped, signals a safety shutdown via the SAFETY line previously described.

TA253 is the main output shutdown device and is normally OFF. When OFF, the +5Vr
supply is present on the cathode of DA250. The nominal voltage on the anode is about
+3.7V, it is turned OFF and the audio safety circuit is in monitor mode. When TA253 is
turned ON, the collector goes to ground turning DA250 ON and pulling the non-inverting
input of IP190B low. IP190B-7 now follows the inverting pin by going low, causing TP210
to turn on and the main supply shuts down as previously described.

Monitoring the audio IC output is a voltage divider between IA002-2 and IA002-4 and is
set up consisting of RA250/RP263 for the left output, IA002-2, and RA251/RP263 for the
right output IA002-4. If either output shorts during high current demand, the output could
either go towards the positive supply rail (+UA) or the negative supply rail (-UA). If the
line goes positive, TA250 will turn on turning on TA252. When TA252 turns on, TA253
also turns on and the safety circuit is enabled. If the line goes negative, TA251 turns on
turning on TA252 and TA253 enabling the safety circuit.

There is also additional protection against loss of either Audio Power Supply or conditions
that may put the negative or positive supply rails out of regulation. The two rails are
connected via voltage divider RP253/RP263 with the common point connected to T A250-B
and T A251-E. If the negative rail disappears or dips too far , TA251 will turn on and activate
the Safety circuit. If the positive rail disappears or dips too far, TA250 turns on and
activates the Safety Circuit.

All audio safety modes are self healing. Once the condition is corrected, the safety circuit
will reset itself allowing normal chassis operation.

RA261

100

RA256

470

RA255

47K

RA254

47K

+5Vr

Run: +5V
Safety: 0V

TA251TA250

RA259

10K

RA257

390K

RA262

100

DA250

TA252

Run: 0V
Safety: +5V

RA260

100

RA258

100K

Run: +5V
Safety: 0

TA253

0V

Nominal

SAFETY_AP

SSB Board

L Spk

R Spk

Out

Out

RA250

RA251

100K

100K

RA263

8.2K

RA252

100K

+UA

-UA

RA253

100K

ITC222 Safety Shutdown

Figure 15; Safety_AP

30

OVER VOLTAGE PROTECTION

To monitor the standby supplies and protect against overvoltage conditions, 1/2 of IP190
is used to compare voltages between the +6Vr supply and the +5Vs supply. The non­inverting input, IP190A-3, is connected to the +5Vs supply and normally runs at about
+4.8V. The inverting input, IP190A-2, is connected to the junction of a precision voltage
divider network (RP203/204) that is directly across the +6Vr supply. IP190A-2 rests at a
nominal +4V when the supply is properly regulated. If that supply increases, IP190A-2
also increases. If it rises above IP190A-3, the output, (IP190A-1) will be pulled LOW.
That turns on TP210, turning on TP161, causing shutdown of the main PWM run supplies.

To TP210
RUN: +4.8V

SHUTDOWN:0V

Figure 16; Over Voltage Protection

+5Vs

RP201

3300

3

1

IP190A

+

-

2

OVER VOLTAGE

PROTECTION

RP202

10K

RP204

4.75K

+6Vr

RP203

2.43K

+4V

Nominal

The final part of the start up protection circuit is the other half of Op-Amp IP190, IP190A.
The inverting pin, IP190A-2, is tied to a reference voltage consisting of resistor divider
network (RP203/204) between the +6Vr supply and ground. That places about +4.0V on
IP190A-2. The non-inverting pin, IP190A-3, has the +5Vs supply on it. If the +6Vr supply
increases, the voltage on IP190A-2 also increases. When it increases to about +7.8V the
Op-Amp inverting pin rises above the non-inverting pin and pulls the output, IP190A-1, to
ground. 0V on the output will trigger the shutdown circuit via TP210 as previously described.

Again, an indication the set is in shutdown rather than normal standby is the output voltage
on IP190. During run operation, it is around +4.8V. In standby, it will stay around +1.0V.
During shutdown, the opamp will pull the output very close to ground.

ITC222 Safety Shutdown

31

20

POWER SUPPLY VOLTAGE LOSS–SAFETY PTV CRT

New to the ITC222 is the addition of a CRT board interconnect that will shutdown the
chassis in the event any single CRT board is disconnected. While the protection circuit
itself is relatively simple, tracing voltages across two main circuit boards, through the
CRT boards and back again is somewhat tedious. Note the +20V r supply is interconnected
via the three CRT boards. That interconnect will be described in greater detail later.

Vr

+

IP540

+9V

IP510

+8V

TP520

+5V

TP530

1.8V SW

IP530
+3.3V

IT630

+3.3V DVI

IC001

+3.3V Cr

IK205

3.3V CSPI

DP540

DP510

RP538

10K

DP530

DT601

DC001

DK206

Part of

Safety_PTV

Interlock Circuit

+3.7V

RP540

4700

RP544

4700

RP521

4700

RP530

3300

RP526

470

RP531

100

SENSE_3V3A

RP543

100

+14.7V

+8.6V

+5.6V

20 20

Part of

Part of

BP500

BP005

+3.5V

PS Supply Monitoring

+5Vs

RP190

18K

SAFETY

5

RP193

470

RP196

22K

6

+

-

RP210

2200

DP211

RP189

1K

RP200

47K

IP190B

+5Vs

RUN: +4.8V

Shutdown: 0V

7

RP213

10K

RP213

10K

RP199

22K

RP212

10K

RP162

10K

+3V

+5Vs

TP210

Pwr On

To Pw r On
Switch TP161
ON (RUN): Low
Shutdown: >+2V

From

Safety_AP

SSB Board PSD Board

Figure 17; Power Supply Loss

All run supply voltages are monitored either directly or indirectly so that in the event one
supply short circuits, all other supplies will be shut down to prevent other catastrophic
damage from cascading failures. The circuit can only protect against further catastrophic
damage in the event of a power supply short circuit. Overvoltage conditions are monitored
by other circuitry.

The supply monitor line consists of a simple voltage divider network: RP540, RP544,
RP521, RP530, and RP531 on the SSB board. Those components are connected directly
across the +20Vr supply (through the interconnect circuit) and common. Diodes DP540,
DP510, DP521, DP510, DP530, DT601, DC001, and DK206 isolate the supplies from

ITC222 Safety Shutdown

32

each other . There is also an input from the Audio Safety circuit (Safety_AP). That circuit
is isolated by a diode and is out of the circuit (showing a high impedance) unless a protection
condition turns the device on. At that point it becomes a low impedance to ground.

The main run supply switch non-inverting input, IP190B-5, monitors the voltage divider
via RP193 and RP526. Note the voltage divider low side voltage will be provided by the
various +3.3V supplies. If all supplies are working the nominal voltage at the junction of
R526/530/531 and on non-inverting pin 5 of IP190B will be +3.7V. The inverting pin 6 is
around +3V so the output of IP190B-7 is high allowing run supply operation.

Under normal run conditions, all the diodes except DP530, DT601, DC001, and DK206
are reversed biased by the lower voltages present on the protection line. This allows the
voltage divider to supply a nominal signal to IP190B-5 that does not disturb the normal
run voltage provided by other bias circuits.

However , if any supply short s or otherwise stop s providing output, the junction of RP530/
531 goes low, pulling the non-inverting input IP190B-5 low. IP190B output on pin 7 will
now track the inverting input and go low, triggering the shutdown circuit.

The +3.3V supply on the SSB board would give similar action as would a short in any of
the supplies on the SSB board. RP540 is a current limiter to make certain there is always
a current path from any short circuit on the power supply sides of the protection diodes.

If shutdown occurs the voltage at IP190B-5 may be monitored giving some indication of
the condition of the supply monitoring circuits. If any supply voltage on the SSB board
shorts, pin 5 will measure different voltages depending on which supply is shorted. The
voltage chart in the table below will assist the technician in determining the problem supply .

Once it is determined one of the supplies in the string is defective, the diodes may be
lifted one by one to determine which supply is shutting the chassis down. It should also
be noted overvoltage conditions cannot be detected by this system. Overvoltage simply
continues to reverse bias the blocking diodes in the system and must be detected by
other means. Overvoltage shutdowns will not occur as a result of this monitoring circuit.

Safety Shutdown Device Resistance to GND

Sense_3V3 IC001-2 .5K
Sense_2V5 IC006-2 .4K

+3V3 IP530-2 .57K

+5V TP520-S 160 Ohms
+8V IP510-3 1.5K
+9V IP540-3 1.2K

USYS DP110-C 27K

20V DP120-C 3K
10V DP140-C 1.3M

6V DP150-C 1.2M

Figure 18; Power Supply Resistance ChartFigure 17; Power Supply Loss

ITC222 Safety Shutdown

33

SAFETY_PTV INTERLOCK

As previously mentioned, there is an interconnect safety circuit that prevents beam current
in all three CRT’s if any of the kine boards are disconnected. If any part of the interconnect
is broken, there will be no +20Vr available to the Power Supply Monitor circuit. As the
voltage is lost, the monitor circuit stops the run supplies and the chassis shuts down or
refuses to start.

The interconnect circuit may be monitored at any of the connectors noted on the diagram
below. The voltage begins to drop significantly once it enters the SSB board at BV500-1.
At that point it should measure a little less than +20V. On the other side of the SSB, it will
have dropped to around +3.8V.

+20Vr

BV001

BL111

21

11

BP500

BP005

CNT1

21

CNT2

SAFETY

RP193

470

RP196

22K

SSB Board

21

PTV INTERLOCK

Green CRT Board

55

RP540

4700

16

21

2020

2525

PROT1

PROT3

RP544

4700

RP521

4700

RP530

3300

1

BV500

16

SAFETY_PTV_CRT

1

BB201

PROT2

BB203

5

PROT1 PROT1

20

20

Blue CRT Board

BB303

5

JB310

PROT3

20

BB104BB204

20

PROT2

JB110

PSD Board

ITC222 Safety Shutdown

RP526

470

Figure 19; PTV Interlock

34

PROT3

PROT1

5

5

Red CRT Board

PSD Board Green CRT Board SSB Board

+240Vr

Source

Part of

Part of

BL200

BB202

99

RB291

4.7

TB291

RB299

4.7

+239Vr
Supply

RUN: +9.6V
Shutdown: 0V

RB292

1000

RB293

330K

RB294

1000

RUN: +3.7V
Shutdown: 0V

JB223

RB297

10

Part of

Part of

BV11

BV500

JV490

0

66

RV490

22K

IR001

99

TB292

SAFETY_PTV_CRT

HEATER

HIGH

RB296

18K

DB293

+0.7V

TB293

RB295

8200

Figure 20; Safety_PTV_CRT

SAFETY_PTV_CRT (REAR PROJECTION ONLY )

To protect against CRT damage when voltages (or lack of voltages) are present that could
contribute to such damage, rear projection instruments use a specific safety circuit that
triggers a shut off event under conditions that could lead to damage. The circuit has been
changed considerably from the ATC221. The safety circuit is now monitored by the main
micro IR001 pin 99. Pin 99 may be an output or input depending upon whether the
instrument is a DV or PTV . For PTV it is normally high. A safety shutdown must pull it low.
That can only happen when TB292 is turned on by the safety circuits. If it does usually
Error Code 61 will be logged in the service menu.

Under normal circuit operation the main safety switch, TB292, is biased off by TV293.
TB293 is turned on from a rectifier circuit creating a bias voltage from the CRT Heater
power supply. TB291 is also biased on by the UVid source. TB291-C runs at around
+9.6V.

Note: There are now two conditions which can trigger the safety circuit. The heater
voltage is being monitored by TB293 and beam current is monitored by TB291. TB292 is
configured as an OR switch such that problems in either area will trigger it ON causing
shutdown of the chassis.

The heater supply voltage is tapped and rectified by DB293 through RB296. The resulting
bias voltage keeps TB293 turned ON. If the heater voltage disappears, TB293 will turn
OFF and the bias voltage developed from TB291 will turn on TB292, causing IT001-99 to
be pulled low, triggering a safety shutdown of the chassis.

Under normal operation, the +240Vr supply feeds current to the CRT drivers. If excessive
beam current is drawn, current through RB291/299 also increases dropping the +239Vr
supply faster than the +240Vr side. As current increases, TB291 is turned on harder

ITC222 Safety Shutdown

35

resulting in higher and higher voltage on its collector. This current passes through
RB293/294 and TB293. As current increases in this network, the volt age drop across the
E-C junction of TB293 also increases. Once the voltage across TB293 increases greater
than +0.6V, TB292 turns on and activates the shutdown circuit.

It is important to note that the Heater protection circuit does not function for overvoltage
conditions. If the heater voltage is too high, it will simply turn TB293 on harder keeping
TB292 OFF.

Also, if the Uvid source disappears due to malfunction, there will be no supply voltage to
turn TB292 ON so that condition must be monitored by other means.

PSD Board Green CRT Board SSB Board

+240Vr

Source

Part of

Part of

BB202

BL200

99

HEATER

HIGH

RB296

18K

RB291

4.7

TB291

RB299

4.7

DB293

+239Vr

Supply

TB293

+0.7V

RUN: +9.6V
Shutdown: 0V

RB292

1000

RB293

330K

RB294

1000

RB295

8200

RUN: +3.7V
Shutdown: 0V

JB223

RB297

10

TB292

Part of

Part of

BV11

BV500

JV490

0

66

RV490

22K

SAFETY_PTV_CRT

Figure 20a; Safety_PTV_CRT

IR001

99

ITC222 Safety Shutdown

36

FROM IV400

PIN 25 DAC OUT

Part of
BV001

EHTINFO (XRP)

10

BEAM INFO

13

EW_PROT

15

17

+3.4V

Nominal

RV865

330K

RV845

127K

Nominal

RV835

1000

+2.5V

RV824

18.2K

Nominal

+8Vr

+1V

+5Vs

RV846

475K

RV844

475K

RV826

18.2K

DV822

RV841

10K

RV862

17K

+4.7V

Nominal

+3.8V

Nominal

RV834

18.2K

+5Vs

RV836

53.6K

IV821A

2

-

+

3

+2.9V

Nominal

IV821B

-

6

+

5

RUN: HI
SHUTDOWN: LO

IV820A

2

-

+

3

IV820B

6

-

+

5

+1.25V

Nominal

DV867

1

+8Vr

RV855

2.2K

7

TV852

TV856

1

7

RUN: LO
SHUTDOWN: >+3.7V

DV853

RV867

100

SAFETY_INT

RUN: LO
SHUTDOWN: HI

SAFETY_ENABLE

RUN: LO
SHUTDOWN: HI

78

106

IV400

VIDEO

PROC

IR001
System
Control

ITC222 Deflection Shutdown

Figure 21; Deflection Shutdown

DEFLECTION SHUTDOWN OVERVIEW

There are 6 circuit monitors on the deflection side of the chassis. They are:

• BEAM PROT (Beam Current Under-voltage)

• XRP (excessive HV or beam current)

• EW PROT (excessive power dissipation in the EW circuitry or loss of deflection)

• BEAM (EHT) INFO (HV too Low)

• SAFETY_ENABLE (turns the safety feature off during certain conditions to prevent

false triggers)

• V_GUARD (monitors Vertical Deflection)

For the ITC222, all deflection safety circuits are monitored by the deflection processor,
IV400 via the EHT_INFO input on pin 4. Generally the circuits are engineered such that
any voltage greater than +3.9V ( +0.2) will cause shutdown of the chassis.

Vertical deflection (Vertical Guard) is monitored by Pin 9. Any of the inputs will trigger a
shutdown of the entire chassis.

Pin 5, “FLASH”, which monitored the deflection safety circuits in the ATC221 is not used
in the ITC222.

New to the ITC222 is the use of true differential voltage comparators rather than the Op­Amps used in the ATC221. This provides an open-collector configuration on the output
pins offering the operation of a true switch on the output rather than a voltage rail as in the
previous design. The most noticeable advantage of the IC is the open collector outputs
may be connected directly together to achieve true OR logic operation.

ITC222 Safety Shutdown

37

XRP Shutdown

BREATHING

~1.9V

RL306

RL045

511K

27V

LL008

1

CL131
CL130
CL039
CL038

IHVT

RL043

RL305

330K

RL300

220K

10

DL301

DL303

DL302

47

DL043

EXCESSIVE HIGH VOLTAGE

24K

XRP

10

RL044

Part of

Part of

BV001

BL111

1717

RV862

17.8K

RV845

127K

10

+8Vr

RV846

475K

RV844

475K

Figure 22; XRP Shutdown

RV872

2

­IV821A

3

+

RV841

10K

5

+

IV821B

6

-

From
Safety_Enable

Run: 0V
Enable: High

+3.4V

+8Vr

1K

DV867

1

+3.0V

+4.7V

TV852

7

RV852

2200

TV856

RV865

330K

+8Vr

RV870

82.5K

RUN: < +3V
XRP: > +3.9V

DV853

RV867

100

4

25

EHTIN

IV400

VIDEO

PROC

DAC OUT

SSB BoardPSD Board

IV821 provides both Under-voltage and overvoltage protection for the High Voltage circuits.
IV821A monitors the XRP voltage generated by pin 1 of LL008. Pin 10 of the IHVT, the bottom
side of the HV winding provides regulation of the signal generated by the horizontal output. All
beam current must pass through pin 10. Under normal operation, there is about +5Vdc at this
point creating about +26V of DC bias for XRP via DL043, RL044, RL045, and DL301. The +26V
is divided by a resistor network consisting of RV845, RV841, and RV862 providing about +3V
on IV821A3, the non-inverting input. XRP is tripped if the DC bias voltage is either >+30V or
<+22V.

To monitor the voltage, a reference voltage is set up by the junction of a divider network
consisting of RV846/844 between the +8Vr supply and ground. That voltage is set more
precisely by a trimmer voltage output from IV400-25. It results in a reference of about
+3.4V on the non-inverting pin IV821B-6 and inverting pin IV821A-2.

The voltages present on the input pins during run operation result in an output from
IV821A-1 near ground. Since the normal output range of EHT_IN is from 0V to about
+3.0V, DV867 de-couples it from EHTIN. This allows EHT_IN to monitor operation of the
CRT, high voltage and beam current for normal variances. EHT_IN provides beam current
compensation or “Breathing”. With the non-inverting input of IV821B higher than the
inverting input, IV821B-7 output is high. When IV821B-7 is high, TV852 is held OFF.
With no current in the network consisting of TV852/856, DV853 is also OFF and normal
circuit operation of the EHT_IN circuitry is allowed.

If excessive beam current is drawn, the output of the IHVT at pin 10 also increases. As
that voltage increases, the DC bias voltage generated from it also increases raising the
voltage at IV821B-6 and IV821A-3. In this case IV821A-7 is already high, increasing the

ITC222 Safety Shutdown

38

voltage will not make a difference in the output. However, when the non-inverting input
(IV821A-3) increases to greater than the inverting input (IV821-2), the output IV821A-1
goes high. In this case, when it increases to higher than the reference voltage, +3.4V on
IV821A-2, the output on pin 1 goes high. EHT_IN trips when pin 1 goes above +3.9V,
shutting the set down.

If HV decreases too much, the non-inverting pin (IV821B-5) will drop below the reference
voltage on the inverting input (IV821B-6) and IV821B-7 will be pulled low turning ON
TV852. When TV852 turns on, TV852-C goes high forward biasing DV853 triggering the
EHT_IN input, IV400-4, to shutdown deflection.

Note that although both conditions result in chassis shutdown, there are very distinct
differences in how they perform their shutdown routines. Those differences can lead to
better diagnosis.

ABL & XRP

The EHT_IN input at IV400-4 also performs two additional functions. First it is the
compensation for beam current variations, also known as “breathing” or ABL (Automatic
Beam Limiting). ABL operation generally provides voltages at pin 4 between +0.1 and
+3.0V. That variation is translated into horizontal output control which can adjust high
voltage to compensate for differing beam current conditions. In most cases as beam
current increases, HV would tend to dip. The EHT_IN input senses that increase in beam
current and raises HV proportionately to keep horizontal width (along with all other IHVT
derived voltage supplies) constant. If beam current decreases, HV would tend to rise so
EHT_IN would lower HV accordingly.

The secondary function of the EHT_IN input is to monitor the status of XRP related
operation and shut down high voltage in the event of improper operation. If the input
voltage rises above +3.9V, it would indicate excessive beam current and shutdown of
horizontal deflection results. A shutdown initiated by IV400-4 will stop deflection and
place it in “Standby” mode. A restart is possible only via microprocessor command

typically initiated by a manual restart of the instrument.

SAFETY ENABLE

The safety enable circuit acts as a safety defeat during the period of start-up when supply
voltages may be unstable and false shutdowns could occur. At start-up Pin 106 of the
main microprocessor (IR001) goes to high impedance and TV856 is turned on as CV854
charges through RR180. Once the voltage on TV856-B goes above +0.6V it turns ON
grounding EHT_IN (IV400-4). When EHT_IN is low, normal run operation is allowed and
the main safety switch, TV852 is effectively removed from the circuit preventing false
safety shutdowns from any of the comparators.

Once CV854 charges, current flow stops and TV856 shuts off allowing normal safety
operation. CV854 also prevents false shutdown by the microprocessor. If pin 106 goes
to low impedance, the only discharge path would be the B-E junction of TV856 which is
reversed bias by the voltage on CV854 preventing it from turning on. Eventually CV854
will discharge to the low impedance pin 106 but it provides enough reserve to prevent
false triggering of the Safety Enable line.

39

ITC222 Safety Shutdown

VERTICAL GUARD

Beam current without vertical deflection may result in almost instantaneous burns of the
phosphor coating of a CRT. T o stop beam current in the event of vertical scan failure or if
deflection problems exist which could result in loss of vertical scan, the ITC222 now
monitors the vertical flyback pulse from the vertical output IC and its power supply. The
circuit is straightforward and depends on the vertical flyback pulse generated by pin 6 of
the vertical output IC. A sample of that pulse is supplied to the convergence microprocessor
(IK201) to provide sync and for the monitor circuit. If the pulse disappears, IK201 assumes
problems with vertical deflection and signals the deflection processor IV400 of the event.
IV400 immediately shuts down beam current by turning off the RGB drivers via the
SSC_Vertical_Guard line.

SSC_VERTICAL_GUARD

The SSC_Vertical_Guard signal from IV400-9 is normally LOW. When a condition exists
that could cause harmful beam current due to loss of scan, the signal goes HIGH. Although
the circuitry looks complex, it amounts to a simple switch. When IV400-9 goes HIGH,
TV550 turns ON turning ON TV556. TV556 turns on TV503/13/23, effectively opening
the RGB output circuits TV500/10/20. With no drive, the CRT amplifiers shut off beam
current.

Note several of the transistors used in this switching circuit are contained in a dual package
configuration. Pinouts for those devices are noted.

ITC222 Safety Shutdown

40

RF041

V

22K

DF031

6

+13Vr

IF001

VERTICAL

OUTPUT

RF040

1000

ertical Guard

SSC

V GUARD

RUN: 0.6V

Part of

BL111

Figure 23; Vertical Guard

Part of
BV001

SSB BoardPSD Board

RK234

RV951

1K

33

Run: 0V
Enable: High

100

Convergence

SYNCV

28

IK201
Micro

SSC V ertical Guard ITC222

R OUT

40

G OUT

41

IV400

Video Processor

SSC

V GUARD

RUN: 0.2V
Shutdown: >+1.0V

SSB BOARD

9

RV550

2.2K

B OUT

42

+8Vr +8Vr

Part of

TV550

2

RV551

1K

6

1

RV552

6.8K

RV553

1000

Part of

TV556

5

+8Vr

RV501

560

RV504

220

RV503

1M

3

5

3

4

RV554

1000

RV555

1000

RV556

1000

RV513

2

RV523

2

1M

1M

4

6

1

6

1

Part of

TV553

RV514

220

Part of

TV553

RV524

220

Part of

TV556

RV511

560

RV521

560

+8Vr

+8Vr

TV500

TV510

TV520

RV502

10

RV512

10

RV522

10

G OUT

4

R OUT

8

B OUT

14

BV500

Figure 23a; Vertical Guard

ITC222 Safety Shutdown

41

EAST-WEST PROTECT

Excessive power dissipation in the EW correction circuits can signal dangerous deflection
operation or failure of high current components in the EW circuit itself. A signal, EW_PROT,
is generated from the voltage on and around the drain of the EW output FET (TL029) and
the EW current sensed at the source of TL029. The sensing components are carefully
chosen to provide a consistent signal at the junction of CL023, RL023, and RL024 in the
EW circuitry for all valid operating conditions of the EW correction circuitry. That voltage
is monitored by the inverting input (IV820B-6) and is typically +1.0V. A reference voltage
of +1.25V is placed on the non-inverting input (IV820B-5) which results in an open output
condition on IV820B-7, allowing normal operation of the remainder of the deflection safety
comparators and deflection.

If either current or voltage increases at the sense points of TL029 the voltage at IV820B-6
increases. If pin 6 becomes greater than Pin 5 the output of IV820B-7 goes LOW turning
on TV852. That places a HIGH on TV852-C and IV200-4 initiating a shut down of horizontal
deflection.

RL022

From TL029

1000

EW Buffer

+1.1V

PSD Board

EW Protect
SAFETY_ENABLE

15

Part of

BL111

Part of
BV001

+1.0V

EW_PROT

15

+5Vs

RV836

53.6K

RV834

18.2K

SSB Board

RV835

1000

RUN: +8V
SHUTDOWN: <+1V

6

­IV820B

5

+

7

+1.25V

RV857

2.2K

RV855

2.2K

TV856

+8Vr

TV852

RV852

2.2K
RV867

100

RUN: 0V
SHUTDOWN: >+6V

RV854

1000

RV856

10K

DV853

CV854
100uF

RR180

4.7K

+

+5Vs

H SHUTDOWN
RUN: Low
Shutdown: High

4

EHTIN

78SAFETY_INT

106

SAFETY ENABLE

System
Control

IV400
VIDEO
PROC

IR001

ITC222 Safety Shutdown

Figure 24; EW Protect / Safety_Enable

42

SUMMARY

This manual has attempted to cover all safety related shutdown circuitry that could cause
shutdown of the ITC222 chassis or prevent it from starting up. Always remember the
circuits themselves are only monitoring circuits such as those in the deflection and power
supply sections for dangerous operation or catastrophic failure. Understanding the monitor
circuits and following the safety shutdown indications should lead to the actual circuit
failure. Troubleshooting of the failure is still required.

The take away from this manual should be that all normal protection related shutdowns of
the ITC222 chassis are governed by six devices; TP210, IP190, IV400, IV820, IV821, and
the main micro (via TP198), plus circuitry associated with the six devices. In most cases,
these devices are monitoring the shutdown circuitry indirectly by monitoring other devices
or voltages that are directly monitoring the circuits.

IP190 monitors the safety shutdown circuitry that is in turn monitoring the power supplies.
When it detects dangerous operation or catastrophic failure, it uses TP210 to shut down
the main PWM waveform causing the chassis to shutdown.

IP820 and IP821 monitor deflection circuitry and the high voltage generation circuits
shutting down deflection when detecting improper operation. It does so by shutting down
the horizontal output waveform.

All active and passive components listed are accessible from the top of the circuit boards
except TV04 on the bottom of the PTV Adapter board. Although the connectors are also
accessible from the top, it may be more convenient for the technician to make voltage
readings from the bottom.

43

ITC222 Safety Shutdown

Appendix

SSB Component and Test Point Locations

The test points needed to troubleshoot power supply shutdowns are noted on the following
graphics. The graphic may be used as a roadmap to locate the proper devices. Although
connectors BR008/009 are not used for troubleshooting they are shown to better guide the
technician to IV820/821.

The above picture is showing the position of IV820 and IV821 for quick reference.

CARRIERCARRIERCARRIER

BK203

SK201SK202SK203

BE205

KBDVD

BK204

MAINPLUG

1

BP100

PJ750

PJ770

BA204BB203

DVD

11

1

BA103

PT630

GNDGNDGND

H-DEFL.H-DEFL.H-DEFL.

PT630

PT630

PT630

PT630

V-DEFL.V-DEFL.V-DEFL.

PT630 PT630

V-CONV.V-CONV.V-CONV.

H-CONV.H-CONV.H-CONV.

PT220

SVMSVMSVM

PT200

PT210

PT640 PT640 PT640

BB151

BB251

GREEN RED

BB351

BLUE

G

PJ034

B

R

CRT

CRT CRT

RGB

FOCUS BLOCK

GND

FOC

DYN

EHT

BB110

BG103

BB210

BG203

BB310

BG303

FOC INP

EHT

SPLITTER

1

111

BB103

PJ116

PJ027

1

1

BB201

1

BB203

1

BB202

PJ20

PJ117

PJ015

PJ029

1

BB303 BB204

PJ118

PJ106

PJ040

PANEL

FRONT

PG037

PT220

PT220

PT200

PT200

PT210

PT210

110V/60Hz

PJ010

PJ760

PJ780

PSDVD

LL605A

LP650

BP801

PJ362

PSDF

BP802

1

BL670

BL680

LL605

BP610

BP611

to

BE105

SK105 SK101SK102SK103SK104

KDB

SK100

11

BW001 BW002

1

PJ364

BW005

PJ20

PJ700

CAB

BW004

11

BP660

1

BL600

PJ126

LED

TOP

LIGHT

BK102

1

BK103 BK104

PJ129

BP011

BP010

BP001

BQ012

BJ010

FCB

PJ050

BJ011

BJ300

GK201

1

BK203

IR

BP400

BP414

BP604

LP401 LP400

BP401

BP403

BP402

MID ITC222

BP015

BQ009

1

LP050

SPEAKER R

PJ035

PJ130

BA051

BA050

R

BA024

L

PJ045

PJ030

BA021 BA023 BA022

LSC

L

1

11

R

BA012 BA005

1

BA010

AUDIOFRONT

1

DVDFEB

1

11111

BK270 BX420 BX220

CONVERGENCECRT

1

BK290

PHOTO

IR KEYBOARD

BK202 BR001 BR005 BV500

BP501

PJ090

BP150

1

BA001

SUPPLY

POWER

PJ600

LOUD-

SPEAKER

1

PSB

1

BP130

SPEAKER L

PJ087PJ085

PJ151

PJ152

.....PJ088....

8 Sensor Autoconvergence

PJ490

IA002

1

BA002

HEADPHONE

1

IA400

BA401

BA100

MAIN-TUNER/IF

NH101

BP502

MONITOR

BV231

1

1

BX200

INPUT 1/2

1/2

SVHS

BX100

SECOND-TUNER/IF

NH201

1

BX310

SSB

BX400 BX410 BV230

JTAG

1

BR007

1

BR006

SERIELL

POWER

BP500

PJ091

BP005

BL033

PT630

PT630

DEFLECTION

BV001

1

1

PJ092

1

1

BL111

BL300

BL035

BL200

1

PJ015

BL501

PJ373

COMPONENT 1 COMPONENT 2

DVI

AUDIO

BT100

BT600

1

BR360

G-LINK

PJ372

BL500

BF001

1

G2FOC

LL008

EHT

PJ105

PJ100

Interconnect Wiring Diagram

OP-A MPS

The safety circuits of the ITC222 make wide use of IC operational amplifiers or “Op­Amps”. They are used for their extremely high impedance output when off and low
impedance (to ground) when on. It enables them to become very reliable voltage
comparators with an almost digital output between the low and high supply rail.

The term “Inverting” (-) and “Non-Inverting” (+) must be understood in order to successfully
troubleshoot Op-Amp circuitry. It also may be helpful to think of the outputs as Low
Impedance and High Impedance rather than ON or OFF.

For example, Op-Amp A:

+5V

0V

+2.5V

0V

A

uses a single ended +5V supply so its output will rail between +5V and ground. If the
inverting and non-inverting input voltages are the same, the output amplifier will deliver a
quiescent voltage of around 1/2 the supply or +2.5V. In the ITC222, equal input voltages
are never used and its an input situation undefined. The idea is to use the Op-Amp as a
switch that compares two inputs. So the output usually switches between the available
supply voltage and ground.

In Op-Amp B:

+5V

+2.5V

+2.5V

+2.5V

B

both inputs are still equal even though they are no longer 0V. The output will still reach an

average level of around 1/2 the supply voltage.
Op-Amp C,

+5V

5V

0V

C

+5V

operates as it is used in this chassis. The non-inverting input has a higher voltage than
the inverting. That drives the output towards the power supply, or a higher impedance. If
the inverting input had a reference voltage fixed on it of +2.5V, the output would still be
very close to the supply rail. If the inverting input was more than the non-inverting input,
as in OpAmp D,

+5V

0V

0V

5V

D

the output now goes toward the other rail, or ground. The output impedance is very low.
Again, even if the non-inverting input rises to +2.5V or higher, as long as the inverting
input is a higher voltage, the output will remain low.

To simplify the Op-Amps usage in the ITC222 Safety circuitry, refer to the following three
diagrams.

Op-Amp E shows that if any two voltages on the inputs of the Op-Amp are equal, the
output is around 1/2 the supply voltage, in this case +2.5V. As designed, the ITC222
does not use this condition.

+5V

=

E

=

Undefined

(+2.5V)

If the non-inverting input (+) is 0.1V higher than the inverting input (-), the output will go
high. In this case the supply voltage of +5V.

+5V

V+(>.1V)

F

V

+5V

If the inverting input (-) goes at least 0.1V higher than the non-inverting input (+), the
output of the opamp will go low, or reference ground.

+5V

V

0V

V+(>.1V)

G

These voltages may be compared to another using an Op-Amp as a truth table essentially
becoming a digital OR gate with the important difference being the inputs may be any
voltage within the specifications of the IC. So the IC is simply comparing two inputs to
see which is higher than the other and outputting a high (Vcc+) when the non-inverting
input is higher and a low (generally reference ground) when the inverting input is higher.

ACTIVE DEVICE STATE

It is also important to note that in many cases output impedance is the important state of
a device rather than ON or OFF. Remember that when an active device is off, it may still
have an output impedance that could affect circuit operation.

For instance, a transistor that is turned OFF has a high impedance from emitter to collector .
So any circuitry connected to the collector is in an “uncontrolled” state, at least by that
device. Other devices on the line would now be able to exert control. In some cases the
line is allowed to float. If the device is turned ON, the device impedance is typically very
low and the collector will follow the emitter usually taking over control of the line. This
makes it possible to “OR” different circuits together using two or more active devices.

TITC222PTVTroubleshootingGuide

Prepared by
Thomson, Inc for TTE Technology, Inc.
Technical Training Department, INH905
PO Box 1976
Indianapolis, Indiana 46206 U.S.A.