Philips MG5.1E Schematic

Colour Television Chassis

MG5.1E

Contents Page

1 MG99 Light path 2 Introduction 3 Overall blockdiagram 4 Power supply 5 Scan circuits 6 Small signal panel 7 CRT drive circuit 8 Interface panel 9 SIDE JACK panel 10 Audio signal part 11 Digital convergence circuit

2 8 9 11 24 29 69 72 74 75 80

Copyright reserved 1999 Philips Consumer Electronics B.V. Eindhoven, The Netherlands. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, or otherwise without the prior permission of Philips.

Published by LM 9972 Service PaCE Printed in the Netherlands Subject to modification 5 3122 785 10053

2 1. MG99 Light path MG5.1E

1. MG99 Light path

MIRROR

R+G+B

RED

GREEN

BLUE

FRESNAL LENS

LENTICULAR SCREEN

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The MG99 Projection TV uses three single color tubes, Red, Green, and Blue. (Figure 1-1) The output of each tube is projected onto a mirror where it is then reflected onto a viewing screen. The Tubes are converged so the light from each tube strikes the same spot on the Fresnel Lens. The Fresnel Lens equalizes and concentrates the light to provide equal light uniformity across the screen. The Mirror is a first surface mirror type which has the reflective coating on the outside of the mirror. To prevent scratching of this surface, always use a soft cotton cloth to clean it.

Figure 1-1

Personal notes

MG5.1E 1. MG99 Light path 3

OUTPUT

BLACK STRIPING

LIGHT

Figure 1-2

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The Lenticular Lens Screen calumniates the light from the Fresnel Lens. (Figure 1-2) The Lenticular Lens increases contrast by reducing the ambient light by the use of Black Striping. The Prismatic formation of the screen allows for nearly 3X light output as compared to a flat screen. Caution should be used when working with the screen. Damage can easily occur in the form of scratching, or by using certain chemical screen cleaners which can strip the black striping from the screen. To clean the screen, use one drop of dish washing detergent in a small bowl of water. (approximately 2 liters) Wipe the screen with a soft cotton cloth in the direction of the stripes.

Personal notes

4 1. MG99 Light path MG5.1E

C ELEMENT LENS

CRT

LIQUID COOLANTOUTPUT LENS

The Three CRT's are driven by 30KV of high voltage and 15KV of focus voltage. (Figure 1-3) The Tube produces a highly concentrated light output of color. A liquid coolant of Glycol is used to transfer heat from the face of the tube to the surrounding mechanical assembly. The C-element lens seals the Coupling fluid within the coupler. The C-element lens and Coupling fluid are part of the light path and contribute to the properties of the optical system.

Figure 1-3

Personal notes

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MG5.1E 1. MG99 Light path 5

1.1 MG99 LIGHT PATH PROBLEMS

Look at the edges of the screen. They may be bowed inward.

PROBLEM - BOTTOM CORNERS DARK

PROBLEM - BOTTOM CORNERS COLORED

There is no problem with the set. The viewing angle is too high.

Figure 1-4

Personal notes

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6 1. MG99 Light path MG5.1E

1.1 MG99 LIGHT PATH PROBLEMS

Fresnel may be reversed. Carefully remove the fresnel and point the grooves toward the viewer.

PROBLEM - BRIGTH AND DARK LINES ON A WHITE FIELD

Figure 1-5

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Personal notes

MG5.1E 1. MG99 Light path 7

1.1 MG99 LIGHT PATH PROBLEMS

The Fresnel offset is pointing down. The center of the Fresnel should be toward the top of the screen.

PROBLEM- UPPER CORNERS OF THE SCREEN DARK

Figure 1-6

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Personal notes

8 2. Introduction MG5.1E

2. Introduction

The 1999 MG99 PTV chassis is designed for the European market. It is available in a 46 inch (117 cm) and a 55 inch (140 cm) 16 by 9 aspect ratio screen sizes. Selected Video can be displayed in either a 4 by 3, 14 by 9, or 16 by 9 aspect ratios. The set has a viewing angle of 160 degrees. The MG99 PTV is capable of receiving signal from PAL B/G, PAL B/G 6OHz, PAL B/H, PAL D/K, PAL 1, PAL M, PAL N, PAL plus, SECAM B/G, SECAM D/K, SECAM L, AND SECAM Li TV systems. There are four composite video inputs which include three SCART connectors, and a Side Jack panel. The systems that can be applied to these inputs are NTSC 3.58, NTSC 4.43, NTSC Play Back, PAL 4.43, PAL, B/G Play Back, SECAM, and SECAM Play Back. The set is equipped with a Frame and Line doubler to produce a horizontal resolution greater than 800 lines. The picture display is driven by three seven inch Red, Green, and Blue tubes. The Sound system is driven by a 2 times 20 watt power amplifier. A switch in the rear of the set allows the sets internal speakers to be driven by an external amplifier. The following sets will be sold in Europe: 46PP9501/05U.K. and Ireland 55PP9501/05U.K. and Ireland 46PP9501/12Western Europe 55PP9501/12Western Europe 46PP9501/58Eastern Europe 55PP9501/58Eastern Europe These units will be distributed from Philips Bundling Center in Bruges, Belgium.

Personal notes

9 3. Overall blockdiagram MG5.1E

3. Overall blockdiagram

Y_CVBS

SIDE JACK PANEL

MG99 SMALL SIGNAL PANEL

C L

G B

CRT DRIVE CIRCUIT

DELAY

SVM MODULE

BLUE CRT

G B

GREEN CRT

RED CRT

AC SWITCH PANEL

LINE SYNC FRAME SYNC

POWER SUPPLY

CONV R, G, B, FB

LEFT AUDIO

RIGHT AUDIO

+5V STBY +15V STBY

+130V +38V

-38V +33V

+15V

-15V

-7V7

+8V6 +5V2

INTENSITY CONTROL

INTERFACE PANEL

AUDIO AMPLIFIER

LINE DRIVE

FRAME DRIVE

HV CIRCUIT

HV/SCAN PANEL

SPEAKER SWITCH

CONV R, G, B, FB

CONVERGENCE PANEL

LINE SYNC FRAME SYNC

FOCUS/G2 BLOCK

CONV YOKES

FOCUS

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Figure 3-1

10 3. Overall blockdiagram MG5.1E

There are eleven PC boards in the MG99 chassis. (Figure 3-1) They are the Small Signal panel, Side Jack panel, Power Supply panel, Interface panel, SVM module, Blue CRT panel, Green CRT panel, Red CRT panel, High Voltage Scan panel, and Convergence panel.

Whenever AC power is applied to the set and the Mains switch is turned On, the Power Supply panel produces a 5 and a 15 volt standby supplies. When the set is turned On by the channel up button on the Front Keyboard or the Remote Control, the 130 volt, 38 volt, -38 volt, 33 volt, 15 volt, -15 volt, -7.7 volt, 8.6 volt, and 5.2 volt supplies are switched On.

Frame and Line drive from the Small Signal panel is routed through the Interface Panel to the Frame Drive and Line Drive circuits on the High voltage Scan panel. The High Voltage scan panel produces the High Voltage and Sync to the Convergence panel. Focus voltage from the High Voltage circuit is fed to a Focus/G2 block which provides Focus and G2 voltage to the three CRT'S. During the Convergence adjustment mode, Red, Green, Blue, and Fast Blanking from the Convergence Panel is fed to the Small Signal panel to generate the adjustment grid. The Small Signal panel selects video from the Antenna input, one of the three Scart connectors, or the Side Jack panel. The Small Signal panel outputs Red, Green, and Blue drive to the CRT drive circuit located on the Interface Panel. The CRT drive circuit then provides drive for the three CRT panels.

Personal notes

Left and Right channel audio from the Small Signal panel is routed through the Interface Panel to the Audio Amplifier panel. The Audio Amplifier panel has its own separate Switch Mode power supply. The output of the Audio Amplifier is then fed to the Speaker Switch panel which selects between the Audio Amplifier or External Audio from a separate amplifier.

Luminance or Y from the Small Signal panel is fed to a Delay circuit on the Interface panel before being applied to the SVM panel. The Scan Velocity Module speeds up the beam during light to dark transitions in the picture to provide a sharper image.

11 4. Power supply MG5.1E

4. Power supply

AC INPUT CIRCUIT

AC SWITCH PANEL

POWER FACTOR CORRECTION CIRCUIT

STBY POWER SUPPLY

+5V STBY

+15V STBY

ON/OFF

AC power is applied to the set on the Power Supply panel. (Figure 4-1) It is then fed to the Mains switch on the AC switch panel located on the front of the set. It is then fed back to the Power Supply panel and to the Power Factor Correction circuit. If the AC mains is 240 volts, the output of the Power Factor correction circuit is approximately 329 volts DC in standby and 350 volts DC when the set is turned On. The Power Factor correction circuit is turned Off during standby. This is a "HOT" chassis. When troubleshooting this or any power supply, always use an isolation transformer. The Standby Power supply produces a 5 and a 15 volt supplies. It also provides operating voltage for the Power Factor Correction and the Audio Amplifier power supply. The Power Factor correction circuit is turned Off when the set is in the Standby mode. The Main Switch Mode Power supply produces a 130 volt, a 33 volt, a 35 volt, a -35 volt, a 15 volt, and a

-15 volt supply. The Main SMPS and the Power Factor Correction Circuit is switched On by a Low from the Small Signal panel.

Figure 4-1

MAIN SMPS POWER SUPPLY

+15V

-15V

5V2 REG

8V6 REG

-7V7 REG

Personal notes

+130V

+33V +35V

-35V +15V

-15V

+5V2

+8V6

-7V7

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MG5.1E 4. Power supply 12

TO AC SW BD

1221

1000 5A

2000 680n

3011

The applied AC voltage is fed to a 5 amp fuse and then to the Mains switch on the AC switch panel. (Figure 4-2) The AC voltage is fed to transistor 7000 and then to the Small Signal panel for clock synchronization.

Figure 4-2

5001

3004

3.3M

3005

3.3M

3006 470K

Personal notes

7000

3007

6.8K

+5VSTBY

3008 10K

50_60HZ

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The Standby Supply produces the 5 volt and 15 volt standby supplies. (Figure 4-3) The output of the Power Factor correction circuit PFCOUT is applied to Pin 5 of 7211 through Pins 2 and 4 of the switching transformer 5202. When the supply voltage is first applied, voltage through the internal startup resistor Rs is applied to capacitor 2283 via Pin 4. When the capacitor charges to 5.7 volts, the internal oscillator switches On driving the internal FET switch. When the voltage across capacitor 2283 drops below 4.7 volts, the IC turns Off. This cycle repeats until the 5 volt standby supply turns Shunt Regulator 6205 On. The supply voltage for the IC is then supplied to Pin 4 through

7213. Operating voltage to Pin 5 of 7213, the Audio Amplifier power supply, and the Power Factor correction circuit is supplied by Pin 5 of 5202. During normal operation, the 5 volt standby source is monitored by the Shunt Regulator 6205. If the 5 volt supply should increase, the Shut Regulator will cause more current to flow through the LED inside the opto-isolator

7213. This will reduce the resistance of the transistor inside

7213. As a result, more current will flow through the Sensing resistor inside 7211, which will reduce the On time of the FET inside the IC. This will reduce the output voltage to the correct level. This supply operates at approximately 100 KHz.

MG5.1E 4. Power supply 13

RESET

+5VSTBY

SOURCE

2282

1uF

5234

3245

2210

7209

RESET

3222

+15VSTBY

2270

6204

1098

6200

6207

22uF

3240

1K5

100uF

6236

39K

6231

3247

180

3246

2K4

2213

1000uF

+5VSTBY

2208

100

2226

3223

22n

3239

2K4

3244

33K

6205

SHUT

REGULATOR

7213

3287

470

CONTROL

5214

+5VSTBY

3215

5233

5211

7204

3241

PFC

6K8

7208

GND_C

6201

8.2V

2209

100uF

3230

1K5

2211

3216

6235

2269

100

5202

GND_C

2228

100

3213

10K

GND_C

7206

7205

+5VSTBY

3212

10K

7214

3289

3214

10K

ON_OFF

100K

2284

3288

10n

10K

PFCOUT

Figure 4-3

2206

GND_C

220uF

7211

INTERNAL

SUPPLY

PWM

5.7V

4.7V

5.7V

GND_C

1,2,3,7,8

2283

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GND_C

47uF

14 4. Power supply MG5.1E

To troubleshoot the Standby Supply, first check the supply voltage on Pin 5 of 7211. If there is no secondary voltage and 7211 is working correctly, startup pulses should be seen at Pin 5 of the IC. If the IC is pulsing and there is no secondary voltage, there is a problem with the outputs of 5202 or with the feedback circuit. If 7211 is not pulsing, either the IC or capacitor 2283 is defective.

When the set is turned On, transistor 7214 will turn Off turning 7205 On. This will turn the Optoisolator 7206 On turning transistor 7204 On, switching the operating voltage to the Power Factor Correction circuit. It also switches the operating voltage to the power supply on the Audio Amplifier panel on the line labeled "CONTROL".

Personal notes

MG5.1E 4. Power supply 15

4.1 European power factor correction circuit

AC IN

AC CURRENT

CAPACITOR CHARGE

VOLTAGE

BRIDGE

The input to most switching power supplies consists of a bridge rectifier and a large electrolytic capacitor. (Figure 4-4) When AC power is applied, the Capacitor will charge to approximately

1.4 times the RMS value of the applied AC voltage. This type of supply does not draw current from the AC power source through out the entire AC cycle. When the capacitor charge falls to point "A", the instantaneous value of the AC voltage exceeds the charge of the capacitor. The bridge diodes are then forward biased, causing current to flow from the AC source. Current will continue to flow from the AC line until the AC sinusoidal voltage reaches its peak at Point "B". At this point, the charge on the capacitor will exceed the AC line voltage reversing the bridge diodes. This results in an AC current waveform that is narrow and distorted compared to the AC voltage waveform. Non sinusoidal waveforms have a high harmonic content, with excessive peaks which results in a low power factor of 0.5 to

0.6. Power Factor is a ratio of real power divided by apparent power. Excessive harmonics and peak currents reduce the efficiency of the power distribution system. The MG5.1 Projection TV without Power Factor correction has a high harmonic content of 85 percent, creating a Power Factor of 0.5. Current spikes of 7 amps will also be created in the AC supply. With the Power Factor correction circuit, the peak current is limited to 1.58 amps, with the harmonic content being reduced to 4.5 percent. The Power Factor is increased to 0.99. The ideal Power Factor is one, which occurs when the current is sinusoidal and in phase with the voltage. The European standard IEC1000 limits the current harmonic content of equipment supplied by the AC Mains.

Figure 4-4

CAP

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LOAD

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Personal notes

16 4. Power supply MG5.1E

4.1 European power factor correction circuit

AC INPUT

BRIDGE

CURRENT SENSE

REGULATOR DRIVE

7102

The MG5.1 Power Factor correction circuit uses a Boost regulator to smooth out the current draw from the AC line improving the Power Factor to 0.99, which is accomplished by drawing current from the AC source throughout the entire AC cycle making the current waveform sinusoidal. (figure 4-5) Input to the module is connected to the AC Mains. The output supplies are approximately 350 volts DC to the Main and Standby Switched mode Power Supply circuit. The Boost Regulator circuit produces a higher output voltage than the input voltage. The regulator drive circuit compares 6103's output voltage, the input voltage from the bridge, and the voltage across the current sensing resistors to control the On time of 7104. This will maintain the output voltage at 350 volts DC and limit the input current to acceptable levels. When 7104 is On, current flow through 5109 stores energy in the choke. When 7104 turns Off, 5109 reverses polarity and charges 2110. Using this type of regulation, current is drawn from the AC source throughout the entire cycle, keeping the current waveform sinusoidal. When the AC cycle is at its low point, 7104 is on for a longer period of time. When the AC voltage is at its peak, 7104 is on for a shorter time to store the same amount of energy in 5109 to maintain the output voltage at 350 volts.

Figure 4-5

5109

6103

7104

2110

350V DC OUT

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If the Boost regulator circuit should become inoperative, due to a loss of regulator drive, operating voltage is still applied to the set. The supply voltage to the switching supplies will drop from 350 volt to approximately 329 volts depending on the Mains voltage. Since the customer would not detect a failure, the operation of this circuit should be checked after any repair of the set.

MG5.1E 4. Power supply 17

4.2 Full power factor correction circuit

350V DC OUT

PFCOUT

(329V)

GND_C

2105

3105

470p

5106

5103

6R8

6103

5105

5109

GND_B

2107

3126

3M3

GND_B GND_B

2118

47K

1uF

3125

GND_B

3119

GND_B

2120

7104

3117

220p

10K

GND_B

PFC

2113

3115

100uF

GND_B

6104

3114

5108

19V

(25V)

LATCH

LOGIC

1.28

OUTPUT

VCC

2110

470uF

5107

OVP

V REF

5.11 V

4.3V 3

3134

470K

3108

3M3

3110

39K

3109

47K

5006

3010

5003

2R2

1222-1

5005

3120

5K6

0.23V

IPK

5.11V

5.45V

5.45V5.11V

3127

3118

390

2116

2n2

18K

GND_B

3128

1K8

3123

1K8

2115

.33

3124

330K

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2114

R490

C485

C486

R493

1n5

3121

33K

3111

.22

INST LINE VOLTAGE

33K

STARTUP VOLTAGE

FOR FULL

POWER SECTION

6000

0.36V MAX

3133

0R1

3132

0R1

R491

5004

5007

3131

3130

FROM AC

SW BOARD

1222-4

0R1

GND_B

GND_HA

330K

OSCILLATOR

17 18

7102

1.5-5.5V

GILBERTS

5.11V

MULTIPLIER

COMPARATOR

CURRENT

AMPLIFIER

Figure 4-6

18 4. Power supply MG5.1E

4.2 Full power factor correction circuit

An explanation of the full Power Factor Correction circuit is now given. (Figure 4-6) The Power Factor Correction circuit is a fixed-frequency Pulse-Width modulated boost regulator power supply. Operating frequency is approximately 60 kilohertz. Due to the low power consumption of the set during the standby mode, the Power Factor Correction circuit is turned Off. The operating voltage, PFC, on Pin 19 of 7102 is turned Off. When the set is turned On, the operating voltage is switched to Pin 19 of 7102. Once the circuit is in operation, a 5.11 volt internal reference voltage on Pin 11 is applied to Pin 6 of the IC. Output of the bridge rectifier is fed to the IC on Pins 4 and 7. Feedback from the output circuit is fed to Pin 14 where it is multiplied with the Bridge output. Inputs to the Gilberts Multiplier produce an error signal that is fed to the current amplifier. The Gilberts Multiplier multiplies the bridge output voltage with the output voltage on D438. The 5.11 volt reference is used to provide a clamping reference for the other inputs. Input current is sampled by resistors 3130, 3131, 3132, and 3133. This sample is added to the error signal from the Multiplier going into Pin 8. The error signal is amplified and then compared to the oscillator ramp to determine the reset point for the latch. When the oscillator goes low, the latch is set making output "Q" High. With the other inputs to the AND gate High, Pin 20 then goes High, turning 7104 On. By comparing the input and output voltage, the On time of 7104 is increased when the AC voltage is at its low point to maintain the 350 volt DC output. When the AC input voltage is at its peak, 7104 is On for a shorter period.

Personal notes

The IPK circuit connected to Pin 2 is an overcurrent protection circuit which resets the latch if there is excessive current through the return resistors. This will reduce the On time of

7104. In a like manner, the OVP, Over Voltage Protection, circuit will reset the latch removing drive to Pin 20 is the output voltage exceeds 392 volts.

To check the operation of this circuit when the set is operating correctly, check the PFCOUT voltage. This voltage should be approximately 350 volts. If the output voltage is approximately 329 volts, this circuit is not working. Check the operating voltage on Pin 19 of 7102. Then check the output drive on Pin 20 and at the gate of 7104. There are three grounds on the Hot side of the supply. Ground HA is connected directly to the bridge 6000. Ground "B" is the ground for the Power Factor Correction circuit. If the current sensing resistors 3130 through 3133 should open, this would remove the ground for all the switching supplies and make the set inoperative. Ground "C" is the ground for the switching supplies. When ground "B" passes through the choke 5106, it becomes ground "C".

Startup up voltage for the Full Power supply is taken from the neutral side of the AC mains.

MG5.1E 4. Power supply 19

4.3 Full power supply

+15V

2326

3331

3330

22K

2312

+33V

470P

5305

5304

+130V

PFOUT

2314

6305

2350

2313

22uF

470uF

470P

3446

3346

470R

3345

6315

470R

+35V

2318

100n

2317

1000u

5307

2316

1000u

2315

5306 6306

1516171819

3307

33R

470p

7301

6304

5302

100n

-15V

2332

-35V

5314

100n

1000u

1000uF

2319

FLIP

470p

3308

6302

3310

2307

FLOP

3309

1302

0R47

0R1

330R

6309 5313

202122

GND_C

6303

2311

2308

2331

2330

2319

GND_C

2322

2321

63075308

3305

10K

GND_C

3306

10R

100n

470u

2327

470u

3329

330R

2328

3319

3328

100R

3326

4K7

7303

VCC

6301

2302

3316

GND_C

15K

GND_C

3318

150K

VCC

GND_C

2324

5312

2m2

2323

470p

3315

15K

2.5V

5312

2325

100n

1301

5310

6308

470p

3447

2.7K

3317

15K

7302

3324

150K

3323

2K7

+130V

2334

3325

10K

3327

100R

2303

STARTUP

3300

100uF

22K

3461

27K

GND_C

2333

7303

+5VSTBY

3322

3344

7309

3304

7300

1305

+5VSTBY

470R

130V

10K

ADJ

ON_OFF

3343

3303

100K

2349

10K

6313

3321

SOFT

UNDER

2346

100N

VCC

START

VOLTAGE

LOCKOUT

9.4/14.5

18V

8K2

17V

3320

OVERVOLTAGE

8K2

VCC

GND-C

DEMAG

VCC

OSCILLATOR STANDBY

REFERENCE

SECTION

FROM

STBY

SYNC

2442

2443

1uF

3313

10K

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Figure 4-7

20 4. Power supply MG5.1E

4.3 Full power supply

When the set is turned On, the Main Switch Mode power supply is turned On. (Figure 4-7) This supply produces the +130 volt, +33 volt, +35 volt, -35 volt, -15 volt, and +15 volt supplies. When the On/Off line goes Low, transistor 7309 is turned Off, turning transistor 7300 On. This switches relay 1305 On. Startup voltage from the neutral side of the AC mains will charge capacitor 2303 to 14.5 volts which will overcome the undervoltage lockout of IC 7302. After the Soft Start capacitor 2443 charges, the oscillator inside the IC will turn On. Each cycle of the oscillator will set the flip-flop which will cause Pin 3 to go High. This will turn the FET switch 7301 On. Voltage is applied to the Drain of 7301 through Pins 4 and 8 of 5300 from the Power Factor Correction circuit. Current through sensing resistors 3308 and 3309 will develop a voltage which is applied to comparator "B" connected to Pin 7. When the voltage on Pin 7 reaches the reference voltage on the inverting input, the FlipFlop will be reset. The voltage on the inverting side of comparator "B" is limited to 1 volt. Therefore, the ramp voltage on Pin 7 will not exceed 1 volt. The circuit will continue to operate until the charge on capacitor 2303 falls below 9.4 volts shutting the IC Off. Each time 7301 is turned On, energy is stored in transformer 5300. Voltage from the Hot secondary on Pin 10 is rectified by 6301. When the output of this circuit has sufficient energy to maintain 2303 above 9.4 volts, the IC then operates in steady state.

Personal notes

When IC 7302 develops a normal steady state operation, the 130 volt supply is sampled by resistors 3324, 3323, and 3322. This sample voltage is then sent to Shunt regulator 7303 which drives the feedback optoisolator 7303. The feedback voltage on Pin 14 is then compared with an internal 2.5 volt reference by comparator "C". Comparator "C" then sets the reference voltage on the inverting side of comparator "B" to control the On time of the drive at Pin 3. If the voltage on Pin 14 increases due to the 130 volt supply increasing, the On time of the pulse on Pin 3 will be reduced. If the 130 volt supply decreases, the voltage on Pln 14 would decrease, causing the On time of the pulse on Pin 3 to increase. This is used to keep the 130 volt supply at the correct voltage. Variable resistor 3322 is used to adjust the 130 volt supply to the correct level.

The overvoltage protection circuit of the IC will shut the IC down if the VCC level on Pin 1 exceeds 17 volts.

To troubleshoot this circuit, first check the On/Off line from the Small Signal Panel to ensure that it is going Low. Then check for the presence of startup voltage on Pin 1 of the regulator IC

7302. If the IC is working correctly, this voltage will be changing from 9.4 to 14.5 volts. If the startup voltage is not present, check the startup resistor 3300 and the bridge rectifier. If the voltage on Pin 1 is changing, check the drive signal on Pin3. Then check for signal on the gate and drain of 7301. An excessive load on the secondary, a short on the 130 volt line for example, would cause the supply to pulse with little or no voltage on the secondary.

MG5.1E 4. Power supply 21

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TO SCAN

HIGH VOLTAGE

AUDIO

AMPLIFIER

CONVERGENCE

PANEL

CL 96532100_052.eps

INTERFACE

PANEL

50/60 HZ

STBY RTN

+5V STBY

-7V7

SSGND

SS GND

5V +8V6

4 3

+15V

130V RTN +130V

1202

160V DCNC160V RTN 1

CONTROL

+15V

-35V

RTN

+35V

-15V

15V RTN

+15V

+15V RTN

+5V STBY

STBY RTN

ON/OFF

1203127612121205

234

56789

1210

POWER

SUPPLY

567

PANEL

1222

1221

+130V 4

+130V

+130V RTN 213

1220

+130V RTN

SS GND

+5V2

MG99

+8V6

5V STBY

SMALL

SIGNAL

PANEL

+33V

+15V

ON/OFF

Figure 4-8

AC SW BOARD

22 4. Power supply MG5.1E

4.3 Full power supply

The Power Factor Correction, Standby, and Full Power circuits are all located on the Power Supply panel. (Figure 4-8) The Standby supply feeds the 5 volt standby supply to the Small Signal panel via Pin 5 of connector 121 0. The Standby voltage is present whenever power is applied to the set and the Mains switch is On. The On/Off Command from the Small Signal panel is fed to the Power Supply on Pin 8 of connector 121 0. This Pin will measure 5 volts when the set is in the standby mode and 0 volts when the set is turned On. The +33, +15, +8.6, and +5.2 volt supplies to the Small Signal panel are developed after the set is turned On. The +130, +15, +8.6, -7.7, and 5 volt standby voltages are fed to the Interface panel on connector 1202. The 50/60 Hz signal is a sync signal from the AC power mains which is used to provide sync to the clock circuit on the Small Signal panel. 350 volts from the Power Factor Correction circuit is fed to the Audio Amplifier on connector 1203. The Control line on Pin 4 of 1203 provides the operating voltage for the switching power supply on the Audio Amplifier panel. This Control voltage is switched Off when the set is in the Standby mode. Connector 1276 routes power to the Convergence panel while connectors 1212 and 1211 feeds power to the Scan High Voltage panel.

Personal notes

MG5.1E 4. Power supply 23

4.3 Full power supply

AC INPUT

BRIDGE

CURRENT SENSE

REGULATOR DRIVE

7102

The +15 volt source is fed to transistor 7308. (Figure 4-9) This is a Buck Switch regulator circuit which produces the 5.2 volt source. Transistor 7308 is turned On and Off by the Switching regulator IC 7307. To maintain the 5.2 volt source at the correct voltage, the output is sampled and fed to Pin 5 of the IC. The voltage on Pin 5 is then compared with an internal reference. This drives the Pulse Width Modulator which controls the On time of 7308.

Figure 4-9

5109

6103

7104

Personal notes

2110

350V DC OUT

CL 96532100_086.eps

121199

The -15 volt source is fed to linear regulator 7305 to produce the -7.7 volt source. The +15 volt source is also fed to the 8.6 volt regulator 7306 to develop the 8.6 volt source.

24 5. SCAN CIRCUITS MG5.1E

5. SCAN CI RCUITS 5.1Lin e Drive

RED

YOK E

GREEN

YOK E

BLUE

5801

2825

470p

FIL

3818

3865

+240V

+13V

6802

0R47

2815

+130V

2827

2824

680p

1000u

3819

3815

3828

68K

2816

68K

470p

0R27

6801

-13V

6803

2814

3825

2826

1000u

2850

+130V

68u

68K

470p

3867

3823

68K

+28V

6850

2851

100u

2899

4n7

7802

2822

2818

3821

2817

430n

820p

470R

3n3

6806

2811

330p

3814

33R

2834

2819

5805

430n

5804

27n

6808

5803

2805

3681

100n

3452

2K2

YOK E

4R7

3805

+15V

100R

2573

3590

3453

2n2

100K

4R7

2u2 2452

7552

3457

2K2

3454

7553

4R7

7551

3591

3571

3455

3456

2K2

4R7

100R

3458

2K2

2820

4u7

3834

3835

3K3

2836

6830

2837

3806

2838

3837

12K

5802

3839

330K

7830

2839

10n

10u

3812

100K

+130V

2809

100n

3811

3810

2810

2898

2K2

330u

220U

2806

2807

3808

100n

3813

2K2

3807

5800

330R

7803

3829

7801

3809

3830

15R

1509-1

330R

470R

+15V

HDRV

LINE

DRIVE

Figure 5-1

+28V

2801

100n

3803

100R

3840

2800

E_W

7800

3802

3866

3801

68K

18K

27K

1507-4

H_PUL

3800

3890

100R

1K5

1511-1

HFB

3817

470R

HPUL

+15V

1509-7

FBSO

3836

270R

+28V

3831

3832

3K3

7804

3833

100R

HPUL_BLNK

CL 96532100_089.eps

68K

2804

10u

121199

MG5.1E 5. SCAN CIRCUITS 25

5.1 Line Drive

Line Drive from the Small Signal panel is fed to connector 1509 Pin 1 and then to buffer transistor 7803. (Figure 5-1) Transistor 7803 then drives the Line driver transistor 7801. Line drive is then fed to the Line output transistor 7802. Transistor 7802 drives the three Line Yokes and the Scan transformer 5801. The Scan transformer produces a 240 volt supply for the CRT drive circuits, a Filament drive for the CRT'S, a plus and minus 13 volt supply for the Frame drive circuit. It also produces a 28 volt supply for the beam limiter circuit in the High Voltage circuit. The output of the Line Output transistor 7802 is also fed to buffer transistors 7800 and 7804 to produce a Line Sync pulse (HPUL) and Line feedback pulses to the Small Signal panel (HPUL and HFB). The output of transistor 7804 also produces a Line Blanking pulse (HPUL-BLNK).

Drive for geometry correction from the Small Signal panel on the E-W line drives transistors 7553, 7551, and 7552. This circuit drives the return side of the Line Yokes to provide Horizontal corrections to the geometry. Geometry correction drive, E-W, is also fed to transistor 7830 which produces drive for the Dynamic Focus, LV. The Line component to the Dynamic Focus is added in transformer 5802.

Personal notes

The Line Sync (HPUL) is used to synchronize the High Voltage drive. If this pulse is missing, the High Voltage circuit will shut down. A loss of drive to the Line Yokes will cause the High Voltage to shut down.

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