Memorex MT1130C Schematic

Service Manual

MT1130C

13” Color Television

THIS SERVICE MANUAL IS FOR MT1130C 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))

REMOTE SENSOR

CHANNEL

VOLUME

DOWN UP DOWN UP

5721-026TT37N (A34JFQ90X)

POWER

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 25 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: 77 Watts 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 Channels, Freq. Synthesized Remote Control: Infrared, Direct Access 25 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:

• To prevent electric shock, match wide blade of plug to wide slot, fully insert.

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IMPORTANT SERVICE SAFETY INFORMATION

Operation of receiver outside of cabinet or with back remov ed involv es 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 T ransf ormer must be used as a safety precaution and to prev ent 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 r ating 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.

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.

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 de vices 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 f or 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 rev ersed. (If necessary, a non-polarized 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 availab le, this alternate method of measurement should be used. Using tw o 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 .

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 deter mine 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 f or 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:

VOLTMETER 1500 OHMS

0.15 µF

TEST PROBE

TO EXPOSED METAL PARTS

TO KNOWN EARTH GROUND

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 min utes.

3. Connect the antenna leads to the EXT. Antenna Ter minal (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 TP9 from external equipment.

6. If picture and sound do not disappear , check IC301, D552, D553, D554, R554, R555, R556, R557, C555 and C556.

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NOTE: The button combination and position on the Remote Control to select the

( ADJUSTMENT BY REMOTE CONTROL )

ADJUSTMENT MODE

The following adjustment items can be performed from menus by Remote Control as shown below :

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 :

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.

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VIDEOVIDEO

REMOTE CONTROL LAYOUT

METHOD OF RECALL V-BLOCK PASS NUMBER

If user forgets the V-Block Pass Number, call recall by the Service Remote Control or User Remote Control.

1. If use the Service Remote Control, at the Pass Number entry menu, while holding down

[SHIFT] button and press the [Q.REV] button repeatedly four times.

2. If use the User Remote Control, at the Pass Number entry menu, while holding down

[VOLUME DOWN] button on the TV set and press number [3] button on the remote control repeatedly four times.

3. The blinking “?” will be replaced with “!” after each press.

4. Release the [SHIFT] button or [VOLUME DOWN] button and then press [MENU] button. “V-

BLOCK SET” menu will be appearing on-screen with the user setting pass number.

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IC, TRANSISTOR AND CRT COMPLEMENT

INTEGRATED CIRCUITS

IC101 TA87C-B6 Microcomputer IC501 AN5512 Vertical Deflection Output IC102 CAT24CO4 EEPROM IC601 STR30130 AVR IC301 TA1268N IF/Video/Chroma/Deflection IC671 NJ7805LD Voltage Regulator and Reset IC311 NJ7809FA Voltage Regulator

TRANSISTORS

Q101 DTC143ZS Vertical Synchronizing Q452 2SC1473A(R) Blue Color Driver Q102 2SC945(P) Horizontal Synchronizing Q453 2SC1473A(R) Green Color Driver Q173 2SC945(P) SD Signal Buffer Q551 2SC1473A(R) Horizontal Driver Q301 2SC945(P) SIF Signal Buffer Q552 2SD 1 877 Horizontal Driver Q302 2SA733(P) Video Buffer Amplifier Q601 2SC945(P) Power On/Off Relay Driver Q303 2SC945(P) Video Out Q801 2SC945(P) Audio Amplifier Q351 DTC143ZS Service Mode Switching Q802 2SA950(0) Audio Amplifier Q451 2SC1473A(R) Red 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 (183) 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 (158) from CRT

5. Remove Degaussing Coil (L601) from CRT

6. Remove braid wire (331) and spring (157) from CRT

7. Lay cabinet face down on some protective material.

8. Remove 4 CRT mounting screws (174).

9. Remove CRT from Cabinet Front (AA).

10. To install new CRT, reverse above procedure.

11. Perform purity and convergence adjustments.

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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 COLOR AND 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 TP10.

3. Set Tint control to center position. (by Remote Control).

( NOTE: For steps 4, 5 and 6 below, refer to page 3 for Adjustment By Remote Control Method).

4. Go to Adjustment Mode (1) by remote control.

5. Select SUB COLOR and SUB TINT from Adjustment Mode (1) menu screen.

6. Adjust SUB COLOR and SUB TINT level (by using + or - button on remote control) so that waveform 1 & 4 (for SUB COLOR) and waveform 2 & 3 (for SUB TINT) is the same as shown in Figure 2.

FIG. 2

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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 TP9.

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

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