RCA CTC197 Schematic
TO
E8
RED BIAS
VERTICAL
<21-B>
TO
E7
GRN BIAS
E5003
E5007
TP50
RED OUTPUT
194V
FOREWORD
This publication is intended to aid the technician in servicing the CTC195/197 television
chassis. It will explain the theory of operation, highlighting new and different circuits
associated with the digitally controlled chassis. The manual covers power supply,
horizontal and vertical deflection, video signal processing, and audio signal processing
theory of operation along with practical, proven troubleshooting methods. It is designed
to assist the technician to become more familiar with the chassis 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 Consumer Electronics 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 Consumer Electronics 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.
Chipper Check® is a registered trademark of Thomson Consumer Electronics.
dbx® is a registered trademark of Carillon Electronics Corporation.
DSS® is a registered trademark of DirecTV, Inc., a unit of Hughes Electronics Corp.
TV Guide Plus+® is a registered trademark of Gemstar Development Corporation.
TV Guide® is a registered trademark of TV Guide Financial, Inc.
SRS®, the SRS symbol and Sound Retrieval System® are registered trademarks of
SRS Labs, Inc.
First Edition 9726 - First Printing
Copyright 1997 Thomson Consumer Electronics, Inc.
Trademark(s)® Registered Marca(s) Registrada(s)
Printed in U.S.A.
Prepared by
Thomson Consumer Electronics, Inc.
Technical Training Department
PO Box 1976
Indianapolis, Indiana 46206 U.S.A.
®
Contents
General Features: ...............................................................................................................6
Technical Overview .......................................................................................................... 12
CTC195/197 “Main” Power Supply .............................................................................. 15
AC In and Degaussing ..........................................................................................................................15
Power Supply Operation .......................................................................................................................16
Secondary Supply Operation ................................................................................................................19
Troubleshooting ................................................................................................................ .................... 20
Auxiliary Power Supply Operation ............................................................................... 2 2
CTC195 Convergence Power Supply Overview ........................................................... 2 5
Power Supply Operation .......................................................................................................................26
Horizontal Deflection Overview..................................................................................... 30
Horizontal Circuits .......................................................................................................... 32
AFC and APC .......................................................................................................................................32
Horizontal Driver ..................................................................................................................................33
Horizontal Output .................................................................................................................................33
E/W Pin Correction & S-Correction (CTC197) ................................................................................... 35
E/W Pin Correction & S-Correction (CTC195) ................................................................................... 35
X-Ray Protection Circuit ......................................................................................................................36
Z-Axis Correction ................................................................................................................................. 37
Troubleshooting ................................................................................................................ .................... 38
Vertical Circuits................................................................................................................ 40
Half-Supply ........................................................................................................................................... 41
Troubleshooting ................................................................................................................ .................... 45
No Vertical Deflection .......................................................................................................................... 45
Scan Loss Detect & Shutdown Overview ............................................................................................46
Scan Loss Detect Operation.................................................................................................................. 47
System Control ................................................................................................................. 50
Overview ............................................................................................................................................... 50
Standby/AC Line Dropout Detector and Reset .................................................................................... 52
Reset, Recovery, Initialization and BrownOut ....................................................................................52
Software detection ................................................................................................................................ 52
+16V Standby........................................................................................................................................ 52
15 Second Timer ...................................................................................................................................53
POR ( Power Off Reset) .......................................................................................................................53
EEPROM and T4 Chip Power Control ............................................................................................... .54
Main Power Supply On/Off Control.....................................................................................................54
Power Down..........................................................................................................................................56
Batten Down the Hatches .....................................................................................................................56
Feature Auto Detection .........................................................................................................................58
Run Supply Detector............................................................................................................................. 58
Microprocessor Input Signals ...............................................................................................................59
Microprocessor Pin Assignments .........................................................................................................59
U13101 Pin Functions: .........................................................................................................................60
IR Input.................................................................................................................................................. 66
OSD Circuit.......................................................................................................................................... 66
Service Menu ........................................................................................................................................67
Error Codes ...........................................................................................................................................68
Troubleshooting ................................................................................................................ .................... 70
I²C Bus................................................................................................................................................... 70
Main Tuner ....................................................................................................................... 7 5
Input Splitter.......................................................................................................................................... 76
Single Tuned Input Filtering................................................................................................................. 76
RF Amplifier .........................................................................................................................................76
RF Bandpass .......................................................................................................................................... 77
Mixer/Oscillator ....................................................................................................................................77
IF Bandpass ...........................................................................................................................................77
PLL / Frequency Synthesizer ................................................................................................................ 77
Bandswitching....................................................................................................................................... 78
Tuning ................................................................................................................................................... 78
Channel Selection .................................................................................................................................79
Software Control ................................................................................................................................... 80
EEPROM Requirements .......................................................................................................................81
IF Alignment ......................................................................................................................................... 81
IF DACS................................................................................................................................................81
Tuner Alignment ................................................................................................................................... 81
Troubleshooting ................................................................................................................ .................... 83
Electronic Alignment ............................................................................................................................ 83
RF Bandswitching.................................................................................................................................83
Channel Switching ................................................................................................................................85
No Tuning .............................................................................................................................................86
FPIP/2nd Tuner Overview .............................................................................................. 88
Video Input Switching .......................................................................................................................... 91
FPIP (U18100) Overview ..................................................................................................................... 92
FPIP Signal Switching .......................................................................................................................... 93
FPIP IC U18100 Pinout ........................................................................................................................ 96
Second Tuner (PIP) ............................................................................................................................... 98
PIP 2nd Tuner/IF.................................................................................................................................100
T4 Chip U16201.............................................................................................................. 101
T-Chip Overview ................................................................................................................................101
T4 Chip Bus Specifics ........................................................................................................................101
POR (Power-On Reset) Operation .....................................................................................................101
Bus Transceiver Reset.........................................................................................................................101
Transceiver Power Supply and Register Volatility............................................................................. 103
IF Processing .......................................................................................................................................103
Audio Detection ..................................................................................................................................103
CRT Management .............................................................................................................................. 103
Deflection Processing ......................................................................................................................... 103
Video Processing.................................................................................................................................103
Video Processing ............................................................................................................. 104
Luma Processing .................................................................................................................................105
Chroma Processing ............................................................................................................................. 106
RGB Interface .....................................................................................................................................108
External RGB Input Processing..........................................................................................................108
RGB Output Section ...........................................................................................................................108
CRT Management ...............................................................................................................................109
Beam Current Limiting ....................................................................................................................... 109
CRT Drivers ........................................................................................................................................ 110
Automatic Kine Bias & Scan Velocity Modulation..................................................... 111
Scan Velocity Modulation................................................................................................................... 111
Automatic Kine Bias...........................................................................................................................112
AKB Operation ................................................................................................................................... 115
Start-up ................................................................................................................................................ 116
CTC195 AKB ..................................................................................................................................... 117
AKB and Color Temperature Alignment............................................................................................ 118
Audio Processing Overview .......................................................................................... 120
Audio Input/Switching Circuit............................................................................................................122
Balance Control ................................................................................................................................... 122
Volume Taper & Fletcher-Munson Network...................................................................................... 124
Audio Output Circuit ..........................................................................................................................125
AVR (Automatic Volume Reduction)................................................................................................ 127
SRS/Compressor Circuits.............................................................................................. 128
TV Guide Plus+ .............................................................................................................. 1 31
EPG Self-Diagnositcs ......................................................................................................................... 131
Menu’s ................................................................................................................................................. 132
Obtaining More Information...............................................................................................................132
Customizing The Channel Listing......................................................................................................132
One Touch Recording .........................................................................................................................132
Recording Options .............................................................................................................................. 132
Troubleshooting ................................................................................................................ .................. 132
Blank Screen .......................................................................................................................................132
No Sound, Picture Okay .....................................................................................................................133
Can’t Select Desired Channel .............................................................................................................133
Noisy Stereo Reception.......................................................................................................................133
No Picture, No Sound but TV is on.................................................................................................... 133
Sound Okay, Poor Picture ...................................................................................................................133
Black Box Appears on the Screen ......................................................................................................133
TV Guide Plus+ IR Controllers Not Working.................................................................................... 133
TV Guide Plus+ Cable Box Codes .....................................................................................................134
TV Guide Plus+ VCR Codes .............................................................................................................. 134
PTV Digital Convergence Overview............................................................................ 13 6
Circuit Description..............................................................................................................................137
Digital Convergence Circuit ...............................................................................................................140
Convergence Yoke Drivers ....................................................................................................... .......... 142
Crosspoint Adjustments ......................................................................................................................144
Front Panel Service Mode..................................................................................................................145
Remote Control Service Functions............................................................................................... ...... 146
Convergence and Alignment Specifications ...................................................................................... 148
DigiCon Service .................................................................................................................................. 150
T-Chip Alignment ............................................................................................................................... 150
Banding ...............................................................................................................................................151
Digital Convergence Failure ...............................................................................................................152
CRT Replacement ...............................................................................................................................152
Digital Convergence IC ......................................................................................................................153
Convergence "Jumps" ......................................................................................................................... 153
Troubleshooting (General) .................................................................................................................. 154
Troubleshooting Geometry .................................................................................................................154
Troubleshooting Convergence............................................................................................................156
CRT Replacement ...............................................................................................................................156
EEPROM Replacement ...................................................................................................................... 161
Main EEPROM Replacement............................................................................................................. 161
DigiCon EEPROM Replacement ....................................................................................................... 161
DigiCon IC Replacement....................................................................................................................164
Red/Green/Blue CRT's........................................................................................................................ 165
Chipper Check Overview .............................................................................................. 166
Chipper Check Hardware.................................................................................................................... 167
Chipper Check Software .....................................................................................................................168
“Dead Set” Troubleshooting with Chipper Check ............................................................................. 169
Chipper Check Hookup ......................................................................................................................170
Chipper Check Operation ...................................................................................................................170
Diagnostic Function ............................................................................................................................170
Alignments Function ...........................................................................................................................171
Part Replaced Function ....................................................................................................................... 171
6 Overview
General Features:
The CTC195/197 chassis is the latest in the Thomson Consumer Electronics line of
digitally controlled television receivers. It relies on microprocessor control to govern
the entire operation of the television, including consumer operation, system operation,
system monitoring and maintenance. The control circuits are not only responsible for
turning the set on and off, but also for aligning the different circuits such as deflection
and signal. Adjustments that were previously aligned with a potentiometer on other
chassis are now aligned digitally via the microprocessor with the values stored in the
EEPROM (Electrically Erasable Programmable Read Only Memory). The CTC197
will eventually replace a wide range of current TCE chassis', including the CTC169
and CTC176/177 series direct view chassis. Video and audio feature requirements
reflect a range of performance from previous core line products to midrange featured
sets. The basic feature package will include dBx stereo, 8 jack panel, and an on-screen
program guide.
Screen Sizes
The CTC197 covers direct view screen sizes from 27" to 35", measured diagonally.
The CTC195 will be used in PTV screen diagonal sizes from 46" to 61".
The projection television CTC195 chassis utilizes the CTC197 basic chassis plus
additional circuitry to adapt it for projection TV operation. The additional circuitry
consists of the "Digital Convergence" circuit board and it's own dedicated power
supply. The CTC195, unlike earlier PTV's that used analog convergence, uses the all
new "Digital Convergence" circuitry to provide near perfect convergence and linearity.
The CTC195 will replace previous PTV chassis CTC169, CTC178/188 and CTC187.
Video
The video performance of the CTC197 covers both low and mid levels. Models are
specified to include comb filter and S-VHS (where 600 LOR (Lines of Resolution) is
required) or non-comb filter without S-VHS (where 280 LOR is required). Auto
Color and AKB (Automatic Kine Bias) are basic for all chassis versions.
Tuning
CTC197 tuners incorporate the necessary specifications to follow normally accepted
cable TV tuning capabilities and will also meet the latest FCC "cable ready" requirments.
Channel tuning is also enhanced through a Fast Tune option.
Audio
CTC197 audio circuitry includes dBx stereo and is configured for both 1 watt and 5
watt output version. The CTC195 will add a 10 watt audio amplifier.
The CTC197 contains a wide array of consumer selections and controls. Among them
are:
Sleep Timer
The sleep timer has four hour functionality and can be set in increments of fifteen
minutes. The OSD counts down time remaining when the sleep timer function is
enabled. The Sleep Time function also includes a descending audio taper automatically
implemented the last one minute of Sleep Timer operation.
On Screen Time and Channel Display
The On Screen Time and Channel features allows the current time and channel to be
displayed on screen. This feature can be programmed for continuous display through a
menu item (continuous display is not an option on PTV). This includes both AM and
PM selections. In cases where time has not been set, only the channel will be
displayed.
Factory Reset
Resets all consumer picture quality adjustments to one of three factory present conditions.
Auto Program
Overview 7
Automatically locates and enters into memory all active channels.
Commercial Skip
Commercial Skip is user implemented in thirty second increments up to four minutes
and then 60 second increments up to one hour. When CS times out, the programming
will return to the channel that was on screen when CS was initially entered. When CS
is enabled in two tuner PIP sets, the original channel will automatically appear in the
second tuner PIP. When CS times out, PIP is disabled.
Multilingual OSD
The CTC197 will support up to three customer-selectable OSD languages. Languages
will include: English, Spanish or Portuguese.
Alarm Timer
The Alarm Timer feature permits the user to set the TV to come on automatically at a
preset time every day. The TV will automatically turn off after two hours if no
other function is accessed by the consumer (i.e., volume, channel, etc.).
Parental Control
The parental control feature permits the user to engage a secondary scan list with more
limited channel choices. This may be used by parents to control the channel selection
capabilities of the set when they are not able to supervise program selection.
8 Overview
Auto Tune (VCR/Cable/DSS Set-Up)
Auto select allows the user to select which channel or external input should automatically
be selected when the VCR1, VCR/LD or cable/DSS key is pressed on the remote.
Auto select set-up is accessible via on screen menu.
Channel Labeling
Channel labeling is permitted for no less than 28, four-character or 14, eight character
labels.
Channel Directory
The Channel Directory Feature permits up to 28 channels and their consumer input
labels to be displayed on-screen as an index. The channel directory presentation may
consist of more than one display screen.
TV Guide Plus+
Displays program title, length, elapsed time, program description, channel labeling and
EDS (Extended Data Service) broadcast early warning display in areas where the
system is broadcast. A menu item assisting in the selection of “Eastern Standard,
Central Western” standard time will be provided.
Closed Captioning
Field one and Field two of closed captioning are supported (CC1, CC2, CC3, CC4,
T1, T2, T3, T4). CCD enabling is through TV menu selection.
Color Temperature
A three position, user-selectable color temperature switch is available via the on screen
display system.
Interface
The CTC195/197 will support two levels of consumer feature operation. On select
chassis versions, the basic interface will be augmented with an ICON based "Fetch"
Menu. Highlighting and enabling a Fetch Icon automatically implements the set-up
menu of the feature or enables it. Fetch Menu items include: sleep timer, front panel
lockout, parental control, alarm timer, initial setup, and channel directory.
Mute
The Mute feature can be enabled via remote control or TV menu selection. Mute with
automatic CCD (Closed-Captioning) operation is consumer selectable via a menu
selection. When Mute and automatic CCD is selected the consumer CCD preference
will automatically be displayed. If no consumer preference has been noted, CC1 will
be selected. Text will not be permitted as an option.
Front Panel Lock-Out
Front Panel Lock-Out disables the front TV access buttons. It can be enabled through
either the remote control or via menu option. Once enabled, the Front Panel
Lock-Out feature can be disabled through either remote command or by disconnecting
AC power to the set for more than sixty minutes.
Fast Track Tuning
The CTC197 will support, via the front panel or remote, a two speed tuning feature.
When the channel up/down key is depressed, the set will continuously select and tune
the next highest/lowest channel and displays it with OSD for 500 ms. If the channel up/
down key is held down for three or more seconds, the Fast Track Tuning feature is
enabled and the TV will select and tune the next highest/lowest channel at a more rapid
rate.
Cable Ready
Provides the channel capacity to provide the accepted “cable ready” standard.
FPIP
Overview 9
Basic Color PIP (FPIP) will be an optional feature on select chassis versions. PIP
features are similar to the CTC187 implementation including swap, and PIP continuous
move. Channel labeling will only be supported in the main picture. PIP can utilize Aux
1 (or S-VHS) as the second video source. Where a second source is not available,
both the big picture and small picture will be the same. Fast Track tuning is provided
for either small or large pix.
Two Tuner PIP
Two tuner PIP (T2FPIP) will be supported on select chassis versions. T2FPIP
features will be the same as those of FPIP but also include channel labeling of both
main and small PIP. Fast Track tuning is active for both small and large pix. The
CTC197 does not support separate main picture vs PIP color controls.
A/V Jack Panel
The jack panel will include two video inputs, one pair of left and right audio inputs and
an S-Video input jack. There will also be one pair of variable (hi-fi) left and right audio
outputs.
S-Video
Select CTC197 chassis will support S-Video with auto detection of the signal when
there is an active S-Video input. The S-Video input will replace Video Input 1.
10 Overview
POWER
DVD
VCR1
VCR2
SAT
CABLE
AUDIO
TV
REVERSE
RECORD
INFO
VOL
MUTE
1
4
7
FAV INPUT
CLEAR
STOP
2
5
8
0
MENU
PLAY
CH+
CH-
SELECT
FORWARD
PAUSE
SKIP
VOL
GO BACK
3
6
9
ANTENNA
RESET
PIP
MOVE
SOUND
FETCH
CH CTRLSWAP
CRK70 Series Remote Control
Comb Filter
A digital comb filter will be employed on select chassis versions. Comb filter versions
will also support consumer switchable video noise reduction.
No Signal Present
When the TV is placed in the S-Video or Video Input mode, and no signal is present, a
gray screen with the caption "No Signal Present" will be displayed.
dbx/SAP Audio
The CTC197 will support dbx/SAP. SAP (Separate Audio Programming) is a
selectable user feature that is specific to the channel selected. When Commercial Skip
is enabled while on a station broadcasting SAP programming, when the original channel
is retuned, SAP is re-enabled.
Audio Speaker Select
A menu option will permit the customer to turn internal speakers on or off.
Treble/Bass/Balance
Overview 11
The audio treble, bass and balance may be adjusted from the menu system.
SRS (Sound Retrieval System)
Basic SRS is supported via OSD. SRS audio is implemented through the internal
speakers. There is no external SRS speaker terminals.
Front Panel Controls
The front panel will provide Menu, Channel Up, Channel Down, Volume Up, Volume
Down and Power buttons.
Remote Use
The CTC197 uses the CRK70, CRK74, CRK83, & CRK84 remote controls.
12 Overview
Technical Overview
The CTC197 was designed to provide a mid/high end replacement chassis for a broad
spectrum of TCE product line.
The CTC197 chassis begins with a bus controlled, tuner on board concept similar to
the CTC175/176/177 family and begins to expand on this base. The key developments
in the CTC197 are the T4 Chip, the FPIP IC, and a new Stereo IC.
The new T4 (U16201), used in part in the CTC185 chassis, allows more bus control of
adjustments and incorporates AKB (Automatic Kine Bias) and places the calculations
for AKB control with software.
The FPIP IC (U18100) is new to the CTC197 and allows bus control of PIP functions.
Although similar to the DPIP found in the CTC187, the FPIP also incorporates video
switching and a digital comb filter. A significant improvement over previous PIP IC
designs is that it requires no external memory. All RAM is internal to the IC.
The audio stereo decoder IC (U11600) allows bus control of the dBx decoder by the
I2C bus. The tone, volume and balance functions previously performed by a separate
IC, are now included in the stereo IC. In addition, two pairs of auxilliary line level
inputs are available. The IC also contains a "loop out/in" function to facilitate connection
of external processing circuitry such as SRS.
The SRS circuit used in the CTC197 was jointly developed by TCE and Hughes to
provide a lower cost version of the system used in the CTC169 and CTC179.
The tuner uses tuner-on-board technology. The design is very similar to the CTC179
with two exceptions. First, the tuner must meet new FCC Class B requirments. New
shielding was required to meet these specifications. Second, the main tuner uses the
combined PLL/DAC IC first used in the CTC185.
The PIP tuner is similar to the CTC179-2 chassis second tuner.
Signal processing will be familiar to the technician. IF/Video/Chroma processing is
again handled by the T-Chip and very similar to the CTC175/176/177 chassis. The T4
is the latest version. AFT changes from analog to I2C digital control. The 4.5 MHz trap
has been deleted from the IC. An external trap is now required.
The T4 also contains ACC (autoflesh/chroma autocolor control), black stretch, adaptive
coring and the low level AKB functions.
The microprocessor is an enhanced version of the ST9 series previously used in the
CTC187. New features include a new OSD to support the "Fetch" menu icons and an
EPG (Electronic Program Guide). The OSD is an anolog RGB system capable of 512
colors and 255 charactors. There also is increased ROM and RAM space.
The power supply is an isolating, variable frequency/variable pulse-width, switch mode
supply using a separate control IC and MOSFET switch. The design provides for
overcurrent and overvoltage protection. It can also be adapted over a wide range of
inputs (90-270 VAC).
Overview 13
Ant
RF
Splitter
To CRT
Kine CBA
TP15105
TP15107
XRP
Protect
Q14901/
CR14901/
CR14902
IR
Pre-
Amp
Front
Panel
Key
Board
"Run" Reg
U14701
U27905
Main
EEPROM
U13102
Tuner
Aux-1 Vid In
Aux-2 Vid In
TP12704
YB/G/R
TP15103
30
R
31
G
B
32
XRP In
36
&
2nd
Main
Tuner
9
Y/C-Deflection
Beam
Sense
24
TP14901
IR In
5
System
6
Control
7
U13101
8
Std
by
19
3
5
D
5
6
AKB
10
AKB
T-Chip
U16201
28
"Run"
D
23
Aux-1 L In
Aux-1 R In
PIP IF
U27901
42
25
Vid
Out
E/W
Pin
17
34
V-In
Clk
D
SVM
D
13
3
TV Guide
Plus+
13
3
Video
Switch
8
U26901
Main
6
Vid In
D
2
44
D
H
V
Out
Out
15
22
4
3
49
To SVM
on Kine
CBA
10
PIP
Vid In
Clk
4
43
Clk
Aud
Decoder
Audio
(Aux-2)
36
35
13
14
38
Y
C
40
6
TP14101
Reg
B+
TP14303
L
W/B
R
Audio
17
TP14302
Pincushion
37
38
L
R
Stereo/SAP Decoder
U11600
Clk
D
9
10
27
D In
26
D Out
Main
51
Vid
PIP
1
Vid
Y
41
TP14502
U14501
Vert Out
1
V Pulse
3
H-Drive
Q14302/301
3
TP14301
U14801/
Q14802
C14805
3
8
5
13
10
+26V
TP14704
41
R
5
28
Clk
FPIP
Switch
U18100
C
39
S-Video
Out
T14301
6
42
L
39
40
R
L
6
Y
C
3
5
Ext
In
Q14401
Horz Out
6
T14401 IHVT
TP14703
C14504
H-Yoke
14
CRT V
L
Compressor
Data
Clk
From SysCtl
7
11
R
L
Audio Output
U11901
2
L
V-Yoke
5
TP14402
TP14501
21
9
TP14706
R
SRS/
CBA
Norm/En
U13101
4
+13V
SRS
R
Fig. 1-1 CTC195/197 Block Diagram
14 Main Power Supply (CTC195/197)
AC to PTV
F201
120VAC
WF51
CR108
3V
3
Control
Logic
Ref V
Ctl & Over
Load Amp
U14101
PWM Controller
L201
Degauss
Circuit
R145
R122
2
Output
C146
"V" Mon
0 Cross
Detect
Power Supply
CR210
R104
R146
C127
5
WF50
6
CR111
8
R105
1
R147
R149
C208
WF48
R111
WF49
CR102
Q101
R135
C147
R124
R148
WF52
"HOT!"
T101
Np
3
4
Nf
9
8
"HOT!"
"COLD!"
11
Ns1
13
Ns2
15
Ns3
16
12
10
Ns4
"COLD!"
WF56
WF54
CR113
WF53
CR116
CR106
CR107
+31V
(Stdby)
WF55
TP14101
+140V
(Stdby)
+33V
(Stdby)
CR133
33V
-12V
(Stdby)
+16V
(Stdby)
+5V
(Run)
+12V
(Run)
7
6
U14701
Main
Reg
Fig. 2-1 Main Power Supply
See Waveforms Page 21.
2
1
3
2
U27905
1
3
RUN/STBY
FPIP
Reg
(from Sys Ctl U13101-19)
7
6
+5V
(Run)
+12V
(Run)
Main Power Supply (CTC195/197) 15
CTC195/197 “Main” Power Supply
The CTC195 and CTC197 main power supply is a variable frequency/variable
pulse width switch mode power supply (refer to Fig. 2-1). It uses a power supply
controller IC (U14101) that drives the power MOSFET, Q101. The CTC195 &
CTC197 are “cold” chassis and the electrical isolation between the power supply
and chassis is achieved using the ferrite core transformer, T101. Energy is stored
in the transformers primary winding during the power MOSFETS On time and is
transferred to the secondary windings when the MOSFET switches off (flyback
period). The transformer (T101) must expend all it’s stored energy before the
start of the next “On” period of the MOSFET. The power supply is self oscillating
and the frequency is dependent on the load and the AC line voltage. The
frequency can vary between 25kHz and 90 kHz. This supply uses “hot side”
regulation which means that there is no actual physical sampling of the secondary
voltages. The feedback winding (Nf) on the hot side of the transformer is tightly
coupled to the Reg B+ windings on the secondary. Voltage variations in Reg B+
are reflected back into the feedback winding (Nf). The regulator IC U14101 has
its own internal reference voltage. The power supply operates whenever it is
connected to the AC line and supplies current on demand up to its current output
limit. The maximum input power to the supply is 180 watts. A diagram of the
power supply is shown in Figure 2-1.
AC In and Degaussing
The AC input to the supply is passed through fuse F201 and then choke L201. It
then enters the bridge diode, CR210. C208 is the Raw B+ filter capacitor and the
unregulated voltage at this point is approximately 150VDC at 120VAC input.
The degaussing circuit is connected in the line via thermistor RT201 and degauss
relay K201. Power for the relay comes from the +12V RUN2 supply. The +12V
RUN2 supply is only present when the instrument is turned on. The relay K201 is
closed and current flows through the degauss coil and thermister RT201. This
heats the thermistor and reduces the current through the degauss coil. After
approximately 1.5 seconds the current through the thermistor falls enough that the
relay de-energizes allowing the relay to open, ending the degauss cycle.
16 Main Power Supply (CTC195/197)
Power Supply Operation
When the instrument is first plugged into an AC source, approximately 150VDC
Raw B+ is developed by the bridge rectifier diodes and the Raw B+ filter
capacitor C208. This is coupled through the primary winding (Np) of T101 (pin
3) and to the drain of the power MOSFET (Q101) via pin 4 of the transformer.
The source of the MOSFET is connected to ground through R124 (.22 ohm/2
watt). At the instant that the instrument is plugged in, the power supply is not
operating and IC U14101 needs a source of power to turn on Q101 the first time.
IC U14101 pin 6 (Vcc) receives B+ via resistor R104 which is connected to raw
B+.
With B+ applied to pin 6 of the regulator, U14101 outputs a voltage at pin 5 that
is applied to the gate of Q101. This turns the MOSFET (Q101) on for the first
time and results in a current flow through the primary (Np) of T101 and Q101.
The IC senses this current indirectly using a circuit consisting of C146 and R146.
One side of R146 is connected to Raw B+ while the other side is connected to
C146 to form a simple RC network. This network is connected to pin 2 of
U14101. This is the primary current sensing input. The capacitor is held in a
discharged state by pin 2 of IC U14101 until the gate of the MOSFET is turned on
at which time C146 is allowed to start charging. With the MOSFET turned on, the
current increases through it and the voltage on pin 2 of the IC also starts to
increase. When the voltage at pin 2 reaches approximately 3 volts, the IC shuts
off the drive to the MOSFET. At this point, the energy stored in the primary of
transformer (Np) is transferred to the secondary windings. At the same time, the
energy transfer is also coupled back into the feedback winding (Nf) between pins
8 and 9. The voltage developed at pin 8 of T101 is rectified by CR111 and filtered
by C127. This voltage is applied to pin 6 (Vcc) of U14101 and now serves as the
Run Vcc instead of the voltage across R104. The voltage across R104 is only
used during initial start-up. After all of the energy is depleted in the secondary
windings, the voltage at pin 8 of T101 starts to decay down to zero. This
decreasing voltage is applied to pin 8 of the IC through R105. This is the zero
crossing input to the IC. When this waveform goes through zero, it signals the
start of another cycle and the IC turns the power MOSFET back on. Current will
again start increasing through Q101 and the voltage on pin 2 of the IC starts
increasing again.
Once the power supply is operating, a method is needed to regulate the output
voltages. This is accomplished by the feedback input at pin 1 of IC U14101. The
winding on pins 8 and 9 of T101 serves three functions. As already explained, it
serves to power the IC and also serves as the zero crossing input to the IC. Its
third function is to provide voltage feedback information from the secondaries
back to the IC. The physical construction of the transformer is such that the
feedback winding is tightly coupled to the Reg B+ winding on the secondary. For
this reason, the voltage across the winding Nf closely follows the voltage
fluctuations on the secondary. This voltage is rectified by CR102 and filtered by
C147 where it is applied to a precision voltage divider. This divider is formed by
R147 and R149. The output of the divider is connected to pin 1 of the IC U14101.
If this voltage exceeds 400 mV, the IC terminates the drive signal to the MOSFET.
F201
120VAC
WF51
CR108
3V
3
Control
Logic
Ref V
Ctl & Over
Load Amp
U14101
PWM Controller
L201
Degauss
Circuit
R145
R122
2
Output
C146
"V" Mon
0 Cross
Detect
AC to PTV
Power Supply
CR210
R146
C127
5
WF50
6
CR111
8
R105
1
R147
R149
R104
C208
WF48
WF49
R111
Q101
CR102
R135
C147
Main Power Supply (CTC195/197) 17
"HOT!"
T101
R124
8
R148
WF52
"COLD!"
CR116
Ns1
Ns2
Ns3
11
13
15
WF54
16
12
WF56
CR106
CR113
+31V
(Stdby)
WF55
TP14101
+140V
(Stdby)
+33V
(Stdby)
CR133
33V
-12V
(Stdby)
Np
3
4
Nf
9
WF53
Ns4
"COLD!""HOT!"
10
CR107
+16V
(Stdby)
+5V
(Run)
+12V
(Run)
2
U27905
1
3
RUN/STBY
FPIP
Reg
(from Sys Ctl U13101-19)
7
6
U14701
Main
Reg
2
1
3
Fig. 2-1 (Repeated) Main Power Supply
See Waveforms Page 21.
7
6
+5V
(Run)
+12V
(Run)
18 Main Power Supply (CTC195/197)
AC to PTV
F201
120VAC
WF51
CR108
3V
3
Control
Logic
Ref V
Ctl & Over
Load Amp
U14101
PWM Controller
L201
Degauss
Circuit
R145
R122
2
Output
C146
"V" Mon
0 Cross
Detect
Power Supply
CR210
R104
R146
C127
5
WF50
6
CR111
8
R105
1
R147
R149
C208
WF48
R111
WF49
CR102
Q101
R124
R135
C147
R148
WF52
"HOT!"
T101
Np
3
4
Nf
9
8
"HOT!"
"COLD!"
11
Ns1
13
Ns2
15
Ns3
16
12
10
Ns4
"COLD!"
WF56
WF54
CR113
WF53
CR116
CR106
CR107
+31V
(Stdby)
WF55
TP14101
+140V
(Stdby)
+33V
(Stdby)
CR133
33V
-12V
(Stdby)
+16V
(Stdby)
+5V
(Run)
+12V
(Run)
7
6
U14701
Main
Reg
Fig. 2-1 (Repeated) Main Power Supply
See Waveforms Page 21.
2
1
3
2
U27905
1
3
RUN/STBY
FPIP
Reg
(from Sys Ctl U13101-19)
7
6
+5V
(Run)
+12V
(Run)
Main Power Supply (CTC195/197) 19
In this way the output drive signal from pin 5 of the IC is regulated so that 400mV
is maintained at pin 1 of the IC. The voltage divider is adjusted so that this
corresponds to the required Reg B+ (»140VDC).
There are two ways of turning off the MOSFET. First, by exceeding 400mV on
pin 1. Second, the voltage on pin 2 (primary current sense) exceeds 3 volts. Pin
1 senses the output voltage while pin 2 limits the maximum output current. If the
output load increases, then more energy must be stored in the primary of the
transformer. This requires the MOSFET be turned on longer. If it is on too long,
C146 on pin 2 charges above 3 volts and shuts off the drive to the MOSFET,
acting as overcurrent protection.
Now let’s take a look at some of the other components in the power supply. R145
and R122 form a voltage divider from raw B+. This voltage is applied to pin 3 on
the IC and forms a “Voltage In” monitor. If the voltage on pin 3 falls below
approximately 1.0 volt the supply shuts down. This is to protect against “Low
Line” voltages. The R/C/Diode network across pins 3 and 4 of T101 form a
snubber network to help dampen any ringing when Q101 turns on and off.
Secondary Supply Operation
The output voltages on the secondary side of the supply are +140, +16, -12, and
the audio supply which varies depending on which audio system in the unit. The
secondary supplies are operational as long as AC power is applied to the instrument.
Each of these voltages are provided by an individual winding on the transformer
with a single rectifier/filter combination.
A 33 volt low power supply for the tuner is derived from the +140V supply. This
supply is composed of a 33 volt zener diode and filter capacitors. A switchable
+12 and +5 volts are provided by regulator U14701. These are both derived from
the +16 volts. Pin 1 is the +16V input while pin 2 is the input for the +5V. The
+16V at pin 2 is passed through a resistor which drops the +16 down to a lower
value reducing the amount of dissipation in the IC. The outputs are filtered before
being sent to the respective circuits. A unique feature of the IC is that their
outputs are switchable (on or off) by a TTL control signal from the system control
circuit. The outputs of regulator IC can be turned off by pulling pin 3 low. IC
U27905 is the same type of regulator as U14701 but provides the supplies for the
FPIP module.
20 Main Power Supply (CTC195/197)
Troubleshooting
Many of the malfunctions in the power supply can be quickly resolved with
simple resistance and voltage measurements. However step-by-step check lists
for some of the more common problems are provided below. One item in particular
deserves special attention. If the main supply is not running, first check for
presence of Raw B+. This can be checked at the +/- terminals of the Raw B+
capacitor C208. There should be approximately 150VDC at this point. If Raw
B+ is present, connect an oscilloscope to pin 6 of U14101. If you see a oscillating
or varying waveform of approximately 4.5 volts to 12 volts, then the IC is not
getting enough Vcc voltage to run. As C127 charges through R104, the voltage
on pin 6 of U14101 will rise, then fall when IC U14101 attempts to turn on.
At this point, it will begin to output pulses on pin 5 of the IC to turn on Q101. If
the supply does not start the voltage on pin 6 starts to decay and the IC turns off.
This process then repeats itself. The result is an oscillation on pin 6. The most
likely cause is an open CR111. If CR111 is shorted, the voltage on pin 6 would
be very low and there would be no oscillation. In any case, if the voltage is
oscillating on pin 6 then the supply is not starting or is trying to start but not
getting enough Vcc from pin 8 of the transformer to pin 6 on the IC.
Another important area that needs to be addressed is what happens to the power
supply during a heavy load or a short on one of the outputs. During heavy load the
voltage ramp on pin 2 of U14101 exceeds 3 volts and the supply shuts down in the
current limit mode. At this point the power supply then tries to restart and if the
load (or short) is still present, it shuts down again. This sequence repeats itself at
an interval of approximately 1/2 second. A large amount of current will be
flowing through the primary of the transformer as the supply tries to restart which
results in an audible “chirp”. If you hear this, suspect a short on one of the
secondaries such as a shorted horizontal output transistor, etc.
Symptom: Fuse Opens
Check for shorted Q101. If shorted, replace Q101 and check R124. If Q101 not
shorted, check CR210 (bridge rectifier) for short.
If fuse opens again, suspect U14101 and varify Q101.
Symptom: No Raw B+
Check fuse F14201. If open, replace and check Raw B+. If fuse OK, check for
output from bridge diodes (CR14210). If bridge OK, check surge resistor R14203.
Symptom: No Secondary Supplies
Check Raw B+. If Raw B+ not present, go to No Raw B+ check above.
If Raw B+ OK, use scope and check U14101-6 for oscillation. If oscillation
present check for open CR111 or R135. If oscillation not present go to step 3.
Is power supply “Chirping”? If yes, check for shorts on the secondary side of
supply. If no, check for shorted CR111 or shorted R135.
F201
120VAC
WF51
CR108
3V
3
Control
Logic
Ref V
Ctl & Over
Load Amp
U14101
PWM Controller
L201
Degauss
Circuit
R145
R122
2
Output
C146
"V" Mon
0 Cross
Detect
AC to PTV
Power Supply
CR210
R146
C127
5
WF50
6
CR111
8
R105
1
R147
R149
R104
C208
WF48
WF49
R111
Q101
CR102
R135
C147
Main Power Supply (CTC195/197) 21
"HOT!"
"COLD!"
R124
R148
WF52
T101
Np
3
4
Nf
9
8
Ns1
Ns2
Ns3
Ns4
"COLD!""HOT!"
11
13
15
16
12
10
WF56
WF54
CR113
WF53
CR116
CR106
CR107
+31V
(Stdby)
WF55
TP14101
+140V
(Stdby)
+33V
(Stdby)
CR133
33V
-12V
(Stdby)
+16V
(Stdby)
2
1
3
RUN/STBY
U27905
FPIP
Reg
(from Sys Ctl U13101-19)
+5V
(Run)
+12V
(Run)
7
6
U14701
Main
Reg
2
1
3
Fig. 2-1 (Repeated) Main Power Supply
+5V
7
6
(Run)
+12V
(Run)
Main Power Supply Waveforms
22 Main Power Supply (CTC195/197)
Auxiliary Power Supply Operation
The auxiliary power supplies on the Main CBA consist of three (3) regulator IC’s
U14104 (+7.5VDC), U18101 (3.3VDC) and U14601 (+5VDC). Series pass
transistor regulator Q11600 provides the +9.5VDC supply. U14104, U18101 and
Q11600 obtain their input voltages (+12V & +5V) from Main Regulator U14701.
These power supplies are only On when U14701 is power up, which occurs only
when the instrument is turned on. Regulator IC U14601 uses the +16VDC supply
from the Main Power supply and outputs the StandBy +5V for the microcomputer
and EEPROM. This power supply is always present whenever the instrument is
plugged into AC power.
Main Power Supply (CTC195/197) 23
TP14103
+12V
6
U14701
Main
Reg
(Main Pwr Supply)
7
+5V
+16VDC Stdby
DeCoder PCB
(+12V)
(+16V)
TP14601
3
+10V Reg
+9.5V
Reg
C14715
C14714
U23902
Q11600
CR11600
CR14604
2
1
10V
3
1
Main PCB
U14104
+7.5 Reg
1
U18101
+3.3 Reg
U14601
+5 Reg
2
1
3
2
DeCoder PCB
3
2
+9.5VDC
(Run)
+7.5VDC
+3.3VDC
(Run)
+5VDC
C13163
+5VDC
+12VDC
+10VDC
(Run)
(Stdby)
(Stdby)
(Run)
(Stdby)
Fig. 2-2 Auxiliary Power Supply
24 PTV Power Supply (CTC195)
120VAC
(From Main
Pwr Supply)
R0
R1
R2
Q700
4
3
WF62
R14
2W
.39
C05
WF61
U701
CR11
8.2V
Ω
T700
8
7
WF60
1
Q1
R26
U700
Amp
On/Off
Signal
2
Q2
CR717 thru
CR720
R3
+23V
R4
1.2K
R5
10K
R24
1K
R6
ZD1
TR3
From Digital
Convergence
PCB, CR200
R20
CR13
CR14
10V
10K
240K
TR1
D1
Error Det
(-40.5V Ref)
1
WF63
Q5
Q8
R22
C702
R3
11
4
3
WF59
Q3
C14
CR3
WF57
WF58
C700
CR5 R18
R25
R10
CR01
10V
R11
"HOT"
7
T701
1
"HOT"
Q4
WF64
WF65
5
2
3
Q7
Np
Nd1
Nd2
"COLD"
14
Ns1
12
9
Ns2
10
Ns3
11
13
Ns4
"COLD"
Q6
CR9
CR10
CR15
20V
R21
CR16
13V
CR7
CR8
-45VDC
+45VDC
+15VDC
-15VDC
CR12
13V
Figure 3-1 Digital Convergence Power Supply
See Waveforms Page 29.
PTV Power Supply (CTC195) 25
CTC195 Convergence Power Supply Overview
The convergence auxiliary power supply is a variable frequency-variable pulse
width switch mode power supply. AC power is supplied to the rectifier from the
main chassis. The Raw B+ for the PTV power supply is generated by a bridge
rectifier (CR717 thru CR720) and filtered by C702. With Raw B+ applied, the gate
of TR1 begins to charge up through R03 and R22. When the turn-on voltage of the
FET inside U700 (TR1) is reached, the FET begins conducting. With TR1
conducting, current flows through the primary (Np) of the transformer (T701), FET
(U700), and through the current sense resistor R14 (U700-8). The current flowing
through the primary winding causes a electromagnetic field to develop around the
winding of Np (pins 7 and 5). As the field around Np rises a voltage is induced into
winding Nd1 (pins 2 & 3). The voltage developed at pin 2 of T701 is coupled by
R10 and C700 to the gate of TR1 (U700-4). The polarity of this winding is such that
it generates a positive voltage which keeps TR1 conducting. When the current
through TR1 reaches the current limit threshold set by R14 and C05, TR1 is turned
off. When the FET (TR1) turns off, the magnetic field around the winding Np
collapses and the energy stored in the primary of the transformer is transferred to
the secondaries. As the field around Np collapse, a positive pulse is generated at
pin 2 of Nd1 that is applied to the gate of TR1 turning it on again. This will continue
for several cycles until stable oscillation is achieved.
The voltage developed across Nd2 rectified by CR5 and compared to an internal
reference of -40.5V (+/- .5V) at pin 1 of U700. Once operation begins, this
feedback winding controls the duty cycle of TR1. The Nd2 winding is responsible
for regulating the output voltages. The duty cycle of the power supply is altered so
that the voltage across Nd2 is maintained at -40.5V. The secondary supply voltage
windings (Ns1 through Ns4) are wound so they reflect any load changes on the
secondary back to winding Nd2.
During normal operation as the load on the power supply increases, the On time of
the FET increases. This increased On time causes higher currents to flow through
the FET and the primary winding of T701 (Np). When the voltage across R14
reaches approximately +.6V, TR3 (inside U700) turns on. This turns off the FET
and causes the output voltage to decrease. Zener diode CR01 and resistor R11 are
used to compensate for any fluctuations in line voltage that result in changes in the
Raw B+.
26 PTV Power Supply (CTC195)
Power Supply Operation
As mentioned earlier, the power supply starts when the gate voltage of the FET (pin
4 of U700) is allowed to charge up thus turning on TR1. However, the power supply
only needs to run when the instrument is turned on. Transistor Q700 is responsible
for hold the gate of the FET low (OFF) until an On/Off signal is received from the
Digital Convergence CBA. When raw B+ is present, transistor Q700 is biased On
via R700, R701 and R702. With Q700 on, the gate of the FET is pulled low thus
preventing the power supply from starting. The On/Off signal is obtained from the
digital convergence board by rectifying the filament pulse and is approximately
+23V when the instrument is running. This On/Off signal voltage supplies the B+
to the emitter of Q1 via R4. This allows Q1 to turn on providing a current path
through the photo-diode. When the ON/OFF signal reaches approximately 16V,
Q1 allows current to flow through the photo-diode. Initially the current flowing
through the photo-diode of the opto-coupler is supplied by Q3 on the ground end
of the circuit. The components (Q5, C14 and R20) on the base of Q3 form a delay
circuit that that turns off Q3 after a short delay to allow the supply to start and
stabilize. When the +23V is present, capacitor C14 begins to charge up through
R20. As the base voltage of Q5 rises, Q5 turns off, thus turning off Q3 removing
the current path for the photo-diode. By this time the supply is up and running and
the current path for the photo-diode (ground end) is provided via Q4. This allows
the photo-transistor to remain on, keeping the base of Q700 grounded thus keeping
it turned Off. This allows the gate voltage of TR1 to rise and the power supply to
operate normally.
As mentioned earlier, the current path for the opto-coupler during normal operation
is provided by Q1 and Q4. Q4 is turned on only when the +15V and -15V supplies
are within a specific operating range. When an excessive load is put on the supply,
the supply goes into current limiting. In order not to damage the convergence
amplifiers, we need to turn off the supply whenever a major overload or overvoltage occurs. When the +15 of the -15 volt supply drops to approximately 13V
the transistor Q1 is turned off. Since Q3 is already off (after the initial startup delay)
the current path for the opto-coupler is removed. This causes the supply to
immediately turn off until the instrument is turned off and back on again. Monitoring
the +/- 45V is not required since a failure in the convergence amplifier causes a
large enough load on the supply that the current limiting circuit within U700 will
shut down the power supply. Q4 is biased on by the output of the secondary voltage
supplies. In this way the secondary output is monitored for overload on the supplies
or in the event that a supply is lost. Q4 monitors the +15V supplies for “Under 13V”
(CR12) and Q6 monitors for “Over 20V” via CR15. If the +15V secondary output
supply falls below 13V, Q4 turns off. If the +15V rises over 20V, Q6 turns on and
grounds the base of Q4, turning it off causing the power supply to shut down
because Q700 will turn back on. Q7 monitors the -15V supply via CR16. If the
-15V supply rises to -13V (supply falls) Q7 turns on grounding the base of Q4.
Whenever Q4 is turned off, this removes the current path for the photo-diode in
U700. This causes the photo-transistor in U700 to turn off allowing Q700 to turn
back on grounding the gate of the FET (TR1) thus shutting down the power supply.
PTV Power Supply (CTC195) 27
120VAC
(From Main
Pwr Supply)
R0
R1
R2
Q700
4
3
WF62
R14
2W
.39
C05
WF61
U701
CR11
8.2V
T700
Ω
8
7
WF60
1
Q1
Q2
R26
CR717 thru
CR720
U700
Amp
On/Off
Signal
2
R4
1.2K
+23V
R5
10K
R3
TR3
From Digital
Convergence
PCB, CR200
R20
R24
1K
CR14
R6
10K
ZD1
240K
CR13
10V
TR1
D1
Error Det
(-40.5V Ref)
1
WF63
Q5
Q8
C702
Q3
C14
R22
R3
11
4
3
WF59
CR5
C700
R25
CR3
WF57
WF58
CR01
10V
R10
R11
R18
"HOT"
7
T701
Q4
WF64
WF65
5
2
3
1
Q7
Np
Nd1
Nd2
"COLD"
14
Ns1
12
9
Ns2
10
Ns3
11
13
Ns4
"COLD""HOT"
Q6
CR9
CR10
CR15
20V
R21
CR16
13V
CR7
CR8
-45VDC
+45VDC
+15VDC
-15VDC
CR12
13V
Figure 3-1 (Repeated) Digital Convergence Power Supply
See Waveforms Page 29.
28 PTV Power Supply (CTC195)
The differential pair consiting of Q1 and Q2 alos control the turn off of the power
supply. When the On/Off voltage starts to fall, the comparator switches the current
to Q2 when the voltage falls below 16VDC. This allows current to flow into the
base of Q8, turning it on. This discharges the voltage on C14 readying it for the next
ON cycle. Since Q1 is off, current flow to the opto-coupler is stopped. With the
opto-coupler turned off, Q700 turns back on and shuts down the power supply.
Transistor Q2 is responsible for monitoring the +23 volts from the convergence
CBA. If the +23 volts starts to fall, Q2 turns on when the emitter falls below the
level that the base is biased at via R6 and R5. When Q2 turns on the emitter of Q1
is grounded, removing its B+ supply and turning it off. This instantly turns off the
opto-coupler U700. With the opto-coupler off, Q700 turns back on and shuts down
the power supply.
120VAC
(From Main
Pwr Supply)
R0
R1
R2
Q700
4
3
WF62
R14
2W
.39
C05
WF61
U701
CR11
8.2V
Ω
T700
8
7
WF60
1
Q1
R26
CR717 thru
CR720
U700
Amp
On/Off
Signal
2
Q2
R4
1.2K
10K
+23V
R5
R3
TR3
From Di gita l
Convergence
PCB, CR200
R20
R24
1K
CR14
R6
10K
ZD1
240K
CR13
10V
TR1
D1
Error Det
(-40.5V Ref)
1
WF63
Q5
Q8
C702
Q3
C14
R22
R3
11
4
3
WF59
CR5
C700
R25
CR3
WF57
WF58
CR01
10V
R10
R11
R18
"HOT"
7
T701
2
3
1
"HOT"
Q4
WF64
WF65
5
Q7
Np
Nd1
Nd2
"COLD"
14
Ns1
12
9
Ns2
10
Ns3
11
13
Ns4
"COLD"
Q6
CR9
CR10
CR15
20V
R21
CR16
13V
CR7
CR8
-45VDC
+45VDC
+15VDC
-15VDC
CR12
13V
Figure 3-1 (Repeated) Digital Convergence Power Supply
PTV Power Supply (CTC195) 29
Convergence Power Supply Waveforms
30 Horizontal Deflection
Horizontal Deflection Overview
The horizontal deflection system has two main functions in the CTC195/197 chassis.
First, it supplies the current for the horizontal yoke coils providing the energy necessary
to move the electron beam horizontally across the face of the picture tube. Second, it
provides a number of power supplies needed for operation of the chassis and picture
tube.
The horizontal yoke current is provided by a circuit consisting of a switch (HOT), the
primary inductance of the IHVT, a retrace capacitor, the trace capacitor (S-Shaping
capacitor), and the horizontal yoke coils.
The voltage supplies provided by the horizontal deflection system are derived from
secondary and tertiary windings on the IHVT. From the previous discussions of the
power supplies, they are used by the video amplifier, the tuner, the CRT, and the
vertical amplifier.
The low level signal processing circuits for the horizontal deflection system are contained
in the T4 Chip. These include the horizontal sync separator and a two-loop horizontal
AFPC system. The T4 allows bus control of several parameters associated with the
horizontal deflection system including horizontal drive pulse width, AFC Gain, Sync
Kill, and ON/OFF.
The XRP circuit in the CTC195/197 is similar to that of CTC179 and CTC185. A
peak detector sets a latch in the T4 Chip. The latch can then be reset only by I2C
communication.
The T4 Chip also generates the ramp waveform used to drive the vertical amplifier.
Bus-controlled vertical parameters include DC bias, amplitude, linearity, and
S-Correction. The same ramp that is used to generate the vertical driving waveform is
also used to create the parabola used for East-West pin correction. Bus controllable
parameters in East-West pin correction include bias (width), amplitude (pin), tilt, and
top and bottom corner. These same parameters are adjustable in both the CTC195
and CTC197. The CTC195 uses a slightly different method to achieve proper
adjustment due to the Digital Convergence system. Discussion on that is provided in
the Digital Convergence section of this manual.
East-West pincushion correction and horizontal width adjustment are provided by a
diode modulator for the direct view CRT assemblies that do not include yoke pin
correction. The modulator is driven by a linear pincushion driver. The parabola used to
develop the correction waveform is generated in the T4 Chip. The T4 provides bus
control of the horizontal width and pin amplitude as well as horizontal trap and corner
correction. In addition, a voltage developed across the high voltage return resistor is
summed at the pin driver to compensate for the decrease in width that occurs as the
high voltage increases with decreased beam current.
A new feature in the CTC197 chassis is the bus controlled Z-Axis correction. This will
allow Z-Axis correction via the remote control, making it much easier for the user than
prior back panel switches. This circuit is used in 32" and larger direct view instruments.
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