Memorex MT1132 Service Manual
Service Manual
MT1132
13” Color Television
THIS SERVICE MANUAL IS FOR MT1132 SUFFIX A , B ,
C AND D CRT USAGE
SUFFIX A SUFFIX B SUFFIX C SUFFIX D
V451 5721-014ST37N
(37GDA86X)
DY501 4993-117 4993-052 4993-110 4993-124
5721-37CN030T
(370KSB22(SYB))
5721-026TT37N
(A34JFQ90X)
5721-030ZT37N
(A34JXV70X)
FEATURES
w On-screen graphics guide you through setup features and operations
w Automatic programming of channels allows easy selection of stations available in your viewing
area
w Sleep timer programs the TV to turn itself off at a preset time
w One day timer programs the TV to come on once at a preset time
w Weekly timer programs the TV to come on at a preset time every day
w 26 button infrared remote control allows remote operation
w VHF/UHF/CATV tuning allows reception of standard broadcasts or cable TV channels
w Closed caption decoder displays captions or half-screen text
w V-Block function
SPECIFICATIONS
AC Power Input: 120V, 60Hz
AC Power Consumption: 77Watts
Chassis Construction: IC Solid State
Picture Tube: 13” ( measured diagonally )
Speaker: 3.5 x 2 in (90 x 50 mm) Oval, 8 ohms
Tuner: 181 Channel, Freq. Synthesized
Remote Control: Infrared, Direct Access
26 Key, 2 “AA” batteries
Receiving Channels:
VHF 2 - 13
UHF 14 - 69
CATV
Mid Band 14 - 22
Super Band 23 - 36
Hyper Band 37 - 65
Ultra Band 66 - 94, 100 - 125
Sub Mid Band 1, 95 - 99
Cabinet: Monitor Style
Antenna Input Impedance 75 ohm (VHF/UHF) Coaxial Input
CAUTION:
• In case you forget the V-Block Pass Number, reset using the Service Remote
Control. At the Pass Number entry screen, while holding down the [SHIFT] button
press the [Q.REV] button repeatedly four times. The display will change from “????”
to “!!!!”. Release the [SHIFT] button and then press the [MENU] button. V-Block
screen will be display.
• To prevent electric shock, match wide blade of plug to wide slot, fully insert .
- 1 -
IMPORTANT SERVICE SAFETY INFORMATION
- 2 -
Operation of receiver outside of cabinet or with back removed
involves a shock hazard. Work on these models should only be
performed by those who are thoroughly familiar with
precautions necessary when working on high voltage
equipment.
Exercise care when servicing this chassis with power applied.
Many B plus and high voltage RF terminals are exposed which,
if carelessly contacted, can cause serious shock or result in
damage to the chassis. Maintain connecting ground lead
connections between chassis, escutcheon, picture tube dag
and tuner cluster when operating chassis.
These receivers have a “Polarized” AC line cord. The AC plug is
designed to fit into standard AC outlets in one direction only. The
wide blade connects to the “ground side” and the narrow blade
connects to the “hot side” of the AC line. This assures that the
TV receiver is properly grounded to the house wiring. If an
extension cord must be used, make sure it is of the “polarized”
type.
When it is necessary to make measurements or tests with AC
power applied to the receiver chassis, an Isolation Transformer
must be used as a safety precaution and to prevent possible
damage to transistors. The Isolation Transformer should be
connected between the TV line cord plug and the AC power
outlet.
Certain HV failures can increase X-ray radiation. Receivers
should not be operated with HV levels exceeding the specified
rating for their chassis type. The maximum operating HV
specified for the chassis used in these receivers is 25 kV
1.0kV at zero beam current with a line voltage of 120V AC.
Higher voltage may also increase possibility of failure in HV
supply.
PROTECT YOUR CUSTOMER
1. Inspect all lead dress to make certain that leads are not
pinched or that hardware is not lodged between the chassis and
other metal parts in the receiver.
2. Replace all protective devices such as non-metallic control knobs,
insulating fishpapers, cabinet backs, adjustment and compartment covers
or shields, isolation resistor capacitor networks, mechanical insulators, etc.
3. To be sure that no shock hazard exists, a check for the presence of
leakage current should be made at each exposed metal part having a
return path to the chassis ( antenna, cabinet metal, screw heads,
knobs and/or shafts, escutcheon, etc.) in the following manner.
Plug the AC line cord directly into a 120V AC receptacle. (Do not use an
Isolation Transformer during these checks) All checks must be repeated
with the AC line cord plug connection reversed. (If necessary, a nonpolarized adapter plug must be used only for the purpose of completing
these checks.)
If available, measure current using an accurate leakage current tester. (Use
Standard Item No. 25086,21641) Any reading of 0.4 mA or more is
excessive and indicates a potential shock hazard which must be corrected
before returning the receiver to the owner.
If a reliable leakage current tester is not available, this alternate method of
measurement should be used. Using two clip leads, connect a 1500 ohm,
10 watt resistor paralleled by a 0.15 MF capacitor in series with a known
earth ground, such as a water pipe or conduit and the metal part to be
checked. Use a VTVM or VOM with 1000 ohms per volt, or higher
sensitivity to measure this AC voltage drop across the resistor. Any
reading of 0.61 volt RMS or more is excessive and indicates a potential
shock hazard which must be corrected before returning the receiver to the
owner.
It is important to maintain specified values of all components in
the horizontal and high voltage circuits and anywhere else in
the receiver that could cause a rise in high voltage, or operating
supply voltages. No changes should be made to the original
design of the receiver.
Components shown in the shaded areas on the schematic
diagram or identified by the safety mark in the replacement parts
list should be replaced only with exact Factory recommended
replacement parts. The use of unauthorized substitute parts
may create shock, fire, X-radiation or other hazard.
To determine the presence of high voltage, use an accurate
high impedance HV meter connected between second anode
lead and the CRT dag grounding device. When servicing the
High Voltage System remove static charge from it by connecting
10K ohm resistor in series with an insulated wire (such as a
test probe) between picture tube dag and 2nd anode lead (AC
line cord disconnected from AC supply).
The picture tube used in this receiver employs integral implosion
protection. Replace with tube of the same type number for
continued safety. Do not lift picture tube by the neck. Handle the
picture tube only when wearing shatter-proof goggles and after
discharging the high voltage completely. Keep others without
shatter-proof goggles away.
When removing springs or spring mounting parts from tuner,
tuner cluster or chassis, shatter-proof goggles must be worn.
Keep others without shatter-proof goggles away.
SAFETY INSPECTION
Before returning the receiver to the user, perform the following
safety checks:
AC
VOLTMETER
1500 OHMS
0.15 uF
TEST
PROBE
TO EXPOSED
METAL PARTS
X-RAY PROTECTOR CIRCUIT CHECK
PERFORM WHENEVER HIGH VOLTAGE CIRCUITRY OR POWER SUPPLY
CIRCUITRY IS SERVICED.
1. Plug the AC Line Cord (P1) into a AC 120V, 60Hz receptacle.
2. Turn the Power Switch (S101) on and wait for about 10 minutes.
3. Connect the antenna leads to the EXT. Antenna Terminal (TE1)
and select a broadcasting station.
4. Connect DC Digital Voltmeter to TP11 (positive lead) and TP4
(negative lead).
5. Apply DC 11V between TP11 and TP4 from external equipment.
6. If picture and sound do not disappear, check IC301,D552,D553,
D554,R554,R555,R556,R557,C555 and C556.
TO KNOWN
EARTH GROUND
( ADJUSTMENT BY REMOTE CONTROL )
ADJUSTMENT MODE
The following adjustment items can be performed from menus by Remote Control as shown
below :
NOTE: The button combination and position on the Remote Control to select the
adjustment items is given on page 4.
1. Press the SHIFT + ADJ. MODE buttons on the Remote Control simultaneously to bring up
the adjustment mode menu screens shown below.
2. From the menu screen, press the + or - button on the Remote Control to select the item to
be adjusted.
3. Press the MENU button on the Remote Control to enter adjustment mode for the item
selected, and the display shown below appears :
OR
COLOR 32
RED CUTOFF 127
Example:
4. Use the + or - button on the Remote Control to adjust the data for the item selected.
5. When adjustment has been completed, press the SHIFT + ADJ. MODE buttons on the
Remote Control simultaneously to return to the main menu.
- 3 -
VIDEO
VIDEOVIDEO
REMOTE CONTROL LAYOUT
- 4 -
IC, TRANSISTOR AND CRT COMPLEMENT
INTEGRATED CIRCUITS
IC101 TA87C-B2 Microcomputer IC601 STR30130 AVR
IC102 M24CO2B EEPROM IC671 NJ7805LD Voltage Regulator and Reset
IC301 TA1268N IF/Video/Chroma/Deflection IC701 TLP651 Photo-Interrupter
IC311 NJ7809FA Voltage Regulator IC702 TLP631 Photo-Interrupter
IC501 AN5512 Vertical Deflection Output
TRANSISTORS
Q101 DTC143ZS Vertical Synchronizing Q551 2SC1473A(R) Horizontal Driver
Q102 2SC945(P) Horizontal Synchronizing Q552 2SD1877 Horizontal Driver
Q173 2SC945(P) SD Signal Buffer Q601 2SC945(P) Power On/Off Relay Driver
Q301 2SC945(P) SIF Signal Buffer Q701 2SC945(P) External Video In
Q302 2SA733(P) Video Buffer Amplifier Q703 2SC945(P) External Audio In
Q303 2SC945(P) Video Out Q751 2SC945(P) Video Amplifier
Q304 2SA733(P) Video In Q752 2SC945(P) Audio Amplifier
Q351 DTC143ZS Service Mode Switching Q753 2SC945(P) Video Amplifier
Q451 2SC1473A(R) Red Color Driver Q801 2SC945(P) Audio Amplifier
Q452 2SC1473A(R) Blue Color Driver Q802 2SA950(0) Audio Amplifier
Q453 2SC1473A(R) Green Color Driver Q803 2SC2120(0) Audio Amplifier
PICTURE TUBE
V451 37GDA86X CRT (SUFFIX A) V451 A34JFQ90X CRT (SUFFIX C)
V451 370KSB22(SYB) CRT (SUFFIX B) V451 A34JXV70X CRT (SUFFIX D)
CHASSIS REMOVAL
1. Remove 4 screws (177) from Cabinet Back (AB) and remove Cabinet Back from rear.
2. Discharge anode lead at CRT chassis ground through a 10kohm resistor.
3. Disconnect anode lead from CRT.
4. Disconnect CRT Socket P.C. board (PCB-2) from CRT(V451).
5. Disconnect 3 connectors (CN501 (DY501), CN601 (L601) and LCN801) from Main P.C.
board (PCB-1).
6. When replacing chassis, reverse the above procedure making certain that all leads are
fastened in their original places.
CRT REMOVAL
CAUTION: Wear shatterproof goggles and exercise proper handling precautions when working
around high vacuum picture tubes.
1. Remove chassis per instructions under CHASSIS REMOVAL.
2. Remove Convergence Magnet Assembly (MG451) from neck of CRT.
3. Remove Deflection Yoke (DY501) from neck of CRT
4. Remove 3 wedges (142) from CRT
5. Remove Degaussing Coil (L601) from CRT
6. Remove braid wire (331) and spring (158) from CRT
7. Lay cabinet face down on some protective material.
8. Remove 4 CRT mounting screws (156).
9. Remove CRT from Cabinet Front (AA).
10. To install new CRT, reverse above procedure.
11. Perform purity and convergence adjustments.
- 5 -
INSTALLATION AND SERVICE INSTRUCTION
CAUTION: Use an isolation transformer when performing any service on this chassis.
SHUTDOWN CIRCUIT: When the high voltage rises, there are simultaneous voltage increase
developed at terminal 6 of the Horizontal Output Transformer ( T671 ) and applied to pin 29 of IC301. If
excessive high voltage is produced, the increased voltage developed exceeds the rating of zener diode
D552 causing the Horizontal Oscillator to stop functioning and the high voltage system to shut down.
AFT ( AUTOMATIC FINE TUNING ) ADJUSTMENT
1. Connect TV Test Pattern Generator (NTSC signal, Monoscope signal, 70dBu, channel 2) to EXT.
Antenna Terminal (TE1) through TV Channel Signal Generator.
2. Connect wire (+) of DC Digital Voltmeter to TP6 and wire (-) to TP4. (Figure 1)
3. Adjust T202 so that the DC Digital Voltmeter reading is 2.0V ± 0.1V.
FIG. 1
SUB TINT ADJUSTMENT
1. Connect TV Test Pattern Generator (NTSC signal, Color Bar signal, 70dB u , channel 6) to EXT.
Antenna Terminal (TE1) through TV Channel Signal Generator.
2. Connect positive lead of Oscilloscope to TP14 and negative lead to TP4.
3. Connect EXT. trigger of Oscilloscope to R463.
4. Set Tint control to center position. (by Remote Control).
( NOTE: For steps 5, 6 and 7 below, refer to page 3 for Adjustment By Remote Control Method).
5. Go to Adjustment Mode (1) by remote control.
6. Select SUB TINT from Adjustment Mode (1) menu screen.
7. Adjust SUB TINT level (by using + or - button on remote control) so that waveform is the same as
shown in Figure 2.
FIG. 2
- 6 -
SOUND IF ADJUSTMENT
1. Connect TV Test Pattern Generator (NTSC signal, 70dB u , channel 2) to EXT. Antenna Terminal
(TE1) through TV Channel Signal Generator. (Standard modulation is 400Hz at 25kHz deviation for
sound signal.
2. Connect positive lead of DC Digital Voltmeter to TP7 and negative lead to TP4.
3. Adjust T203 so that the DC Digital Voltmeter reading is 4.0V.
COLOR PURITY ADJUSTMENT
For best results, it is recommended that the purity adjustment be made in the final receiver location. If
the receiver will be moved, perform this adjustment with it facing East.
The receiver must have been operating 15 minutes prior to this procedure and the face plate of the CRT
must be at room temperature. The following procedure is recommended while using a Dot/Bar
Generator.
1. Check correct location of all neck components. ( Refer to Figure 3 )
2. Rough -in the static convergence at the center of the CRT, as explained in the static convergence
procedure.
3. Set the Contrast control to minimum position and Brightness control as far maximum as possible
without causing the picture to “bloom”.
4. Apply green raster signal from Dot/Bar Generator to receiver.
5. Loosen the deflection yoke clamp screw and pull the deflection yoke toward the rear of the CRT.
6. Begin the following adjustment with the tabs on the round purity magnet rings set together. Slowly
separate the two tabs while at the same time rotating them to adjust for a uniform green vertical
band at the center of the CRT screen.
7. Carefully slide the deflection yoke forward to achieve green purity (Uniform green screen).
NOTE: Center purity is obtained by adjusting the tabs on the round purity magnet rings. Outer edge
purity is obtained by sliding the deflection yoke forward.
8. Check for red and blue field purity by applying red and blue raster signal alternately from Dot/Bar
Generator to receiver. Repeat steps 2 through 7, if required.
9. Tighten deflection yoke clamp screw.
10. Perform BLACK AND WHITE ADJUSTMENT procedure.
( CW : clockwise, CCW : counterclockwise )
FIG. 3
- 7 -
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