Sony D98 CHASSIS Troubleshooting Manual

D98

OPERATION MANUAL TROUBLESHOOTING MANUAL

CHASSIS

TABLE OF CONTENTS

CIRCUIT DESCRIPTION

D Board (Power Supply Section) ........................ 2

D Board (Deflection Section) .............................. 10

A Board ............................................................... 22

N Board .............................................................. 28

GENERAL TROUBLESHOOTING ......................... 30

P ARTS LEVEL BOARD REPAIR ........................... 41

TRINITRON® COLOR COMPUTER DISPLAY

MICROFILM

- 1 -

CIRCUIT DESCRIPTION

ging

D BOARD POWER SUPPLY SECTION Power Supply Electrical Circuit

The power supply is located on the D Board. It has three modes of operation that are controlled by a microprocessor. The architecture is similar to discontinuous mode flyback converters and has photocoupler feedback for regulating the secondary voltages. Circuit operation and troubleshooting are explained in the following sections:

Operation Modes Secondary Circuitry AC Input Protection Circuits Degauss Circuit Troubleshooting Primary Circuitry

Operation Modes

The power supply has four modes of operation, ‘off’, ‘active off’, ‘suspend’ and ‘active on’. These modes are related to power savings and are indicated by the front panel LED. Additional indications are failure diagnostics and aging mode. The table below lists operation mode, condition and LED status.

Mode Syncs Condition LED

Of f NA AC Switch Off Of f

Active Off No H and V Low Power, Heater Off Amber

Suspend/ Standby No H or V Low Power, Heater On Amber 0.5s<- ->Green 0.5s

Active On H and V Present Phase Locked, Normal Operation Green

Failure 1NA HV or +B Failure Amber 0.5s<- -> Off 0.5s Failure 2 NA H Stop, V Stop, Thermal Failure Amber 1.5s<- -> Off 0.5s Failure 3 NA ABL Failure Amber 0.5s<- -> Off 1.5s

/Self Test No H and V Aging Raster or Test Pattern Green 0.5s<- -> Off 0.5s

Except for AC switch off, all modes of operation are controlled by the microprocessor located on the N Board. The failure modes are detected by the microprocessor and the power supply is forced into active off mode. These functions are discussed later (Deflection).

With the AC cord attached to the monitor and connected to an AC source, the monitor will be off until the AC switch is turned on. When the AC switch is turned on, the power supply starts and is in active off mode. The next step is active on mode. The power saving modes are activated by the microprocessor based upon the presence of either H or V sync. If no sync signals are present, the power supply is set to active off mode. If only horizontal sync is present the power supply moves to suspend mode. If only vertical sync is present the power supply enters standby mode.

Power supply operation control signals are “Remote On/Off” and “Heater On/Off”. Remote On/Off is digital low for active off and suspend modes. Heater On/Off is digital low for suspend mode. Suspend mode is similar to active off mode, but with heater voltage on. To enter active on mode, the microprocessor must set remote on/off to digital high. Heater on/off is also made digital high and the heater is turned on.

Output Off Active Off Suspend Standby Active On

B+ 0 120V 120V 180V

80V 0 55V 55V 78V

16.5V 0 8.7V 8.7V +16.5V

-16.5V 0 -12V -12V -16.5V +12V 0 0 0 +12V

5V 0 +5V +5V +5V

Heater 0 0 3.2V 6.3V

H. Centering 0

- 2 -

AC input and Degauss

CN600

C605

C606

F601

250V

DGC1

VR601

RY601

LF602

C601

R601

C602

C604

C603

R602

AC SWITCH

CN601

DGC2

THP602

TH600

R672

D601

12V

D670

R603

0.68 10W

Q670

R670

R671

1. AC Input Section

The AC input section provides EMI filtering, input protection, surge limiting and CRT degauss operation. An AC switch is also present for complete power off condition.

EMI Filter

The EMI filter comprises X-capacitors C601 and C602, Y-capacitors C603, C604, C605 and C606 and the line filter transformer, LF602. Input protection is provided by F601 and surge current limiting by thermistor TH600 and resistors R602 and R603. Degauss is explained in the next section.

The front panel AC switch is wired electrically between R602 and TH600 and when closed, completes the circuit. This allows the bridge diode, D601, to full wave rectify the AC input voltage.

Degauss Circuit

The degauss circuit is used to demagnetize the CRT. After power on, the microprocessor located on the N Board sets the degauss signal to digital high and through Q607 turns on relay RY601. This allows AC current into the degaussing coil through posistor THP602. The current heats up the posistor and its affective resistance increases, this dampens the current in the degauss coil to nearly zero. Duration time is approximately 5-6 seconds and the microprocessor then shuts off RY601, which disconnects the degauss coil from the AC line. This operation should sufficiently demagnetize the CRT.

2. Primary Circuitry Section

IC601

The heart of the primary section is the AN8037 po wer supply controller, IC601. The following describes the functions of each pin.

Pin 1 – TR - This is TR or transformer reset. Similar to a demagnetization function, this pin detects the falling edge of the primary waveform during relaxation period. It allows the next conduction pulse only after reaching the bottom of the ringing waveform. It contributes to the maximum on time setting.

- 3 -

Pin 2 – OCP - Over current protection. Used to determine the overload level at which the timer latch is activated.

Pin 3 – CF – Oscillator. With a capacitor, determines the switching frequencies. (On/Off times.)

Pin 4 - CLM - Over current protection. If the voltage on this pin (primary current feedback) exceeds -0.18V, the power

supply will enter cycle-by-cycle current limit mode.

Pin 5 – GND- IC ground terminal.

Pin 6 – OUT- Output driver for switching transistor Q602.

Pin 7- VCC- IC supply voltage terminal. This voltage is nominally 17.5 volts during active on mode and 12 volts during

suspend or active off mode. The IC receives starting current via startup resistor (R613) until the auxiliary supply is availab le from T601 VCC winding. If the voltage on this pin exceeds 19.4 volts (OVP), the power supply shuts off and can only be restarted by disconnecting and reconnecting the A C line. Under v oltage lock out (ULV O) occurs when the voltage is less than

9.5 volts.

Pin 8 – SD- Used for OVP and timer latch functions. A capacitor determines the timing for OVP function.

Pin 9 - FB – Feedback terminal.

Operation

The power supply is a flyback type conv erter . It has both PWM and RCC characteristics. T he PWM controls the pulse width of the gate drive. The RCC portion insures that the next conduction c ycle starts at zero v olts. Therefor e, the gate pulse wid th varies and the switching frequency also varies. The on and off timing is determined by pins 3 and 1. Pin 1 detects the zero voltage point or the valley on the relaxation ringing waveform.

When AC is applied to the power supply, start up current is supplied though R613 to pin 7 of IC601. Startup voltage is approximately 15V. After start up, the voltage to pin 7 of IC601 is supplied through D605 connected to T601 pin 8. The f irst mode of operation is active off mode and the VCC will be approximately 12 volts. The output drive pulse frequency will be near 40kHz. or a type of frequency burst mode.

When the power supply enters active on mode, the switching frequency will vary between 65 and 120kHz., depending upon input voltage and power lev el. The VCC le vel will be approximately 17.5 volts. O VP threshold is 19.4 v olts and UVLO is 9.5 volts. Therefore, if the VCC voltage is not correct, the power supply will not operate properly.

Feedback from the secondary side comes through IC603 and is connected to IC601 pin 9. (See diagram on page 5.)

3. Secondary Circuitry Section

The secondary section consists of the following circuits. Rectifier diodes and filters for all output voltages, horizontal centering, +5/12 volt regulator, +5 volt back up circuit, heater voltage regulator, voltage feed back circuit, standby mode feedback, B+ detection and protection circuits. This section will describe each circuit and its function.

Secondary Rectifiers

The secondary rectifiers supply the following voltages, 180V (B+) deflection and video, 80V video, ±16V deflection and regulators and 8 volt heater regulator.

Horizontal Centering

This circuit supplies IC502, which is used to adjust horizontal raster position on the CRT. The horizontal centering circuit consists of fusible resistors R621 and R622, diodes D648 and D649 and filter capacitors C656 and C657. In respect to the secondary ground, the horizontal centering ground is floating and connected to –H DY line. The v oltages in reference to this floating ground are ±8 volts. Care should be taken to not short the floating ground to the secondary ground.

+5/12 Volt Regulator

IC605 is the voltage regulator for +5 and +12 volt lines. The output voltages are supplied to the microprocessor, deflection

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From D601

R606 C615

From D601

D603

R608

R613

Q602

R609

C619

VCC

OUT

IC601

D608

CLM

D605

D615

D633

R615

CCP

17 16

IC606

D656

D653 D654

D655

D652

-16V

-16V PROTECTOR To IC604 16V

16V D651

D650

D649

To HDY-

D648

IC501

Pin5

Q658

Q605

80V 180V

To IC502 Pin 3

D631

16V

IC603

D632

Q656

IC652

REMOTE ON/

OFF

Q657

PWR

SHUTDOWN

R660

R663

R659

R668

C613

180V

T601

SRT

C614

14679

and video circuits. The +16.5 volt and the 8-volt lines supply the input v oltages for +12V and +5V re gulator sections, respectfully. During active off or suspend mode a standby back up circuit supplies the 16.5-volt line to the +5 volt section.

+5V Standby Circuit

Normally , the +8V line supplies the +5V regulator. During activ e off or suspend modes, the voltage supplying the +5 re gulator , IC605, will become very low . In order to pre v ent loss of the +5V, it is necessary to supply a back up v oltage. Supplying +16. 5V line to the regulator through Q601 does this. Note: at this time the +16.5V has been reduced to 8.7 volts.

In Acti ve of f mode, Q607 is off, Q606 is on and Q601 is on. Through Q601, IC605 receiv es its input voltage for +5V. In Acti ve On mode, Q607 is on, Q606 is off and Q601 is off. Since Q601 is off, IC605 must receive the +8 volt line through D610. There is a time delay in this circuit, which is used to insure that during any transitions, the +5V line does not drop out. These components are C636, R638 and D619.

Heater Voltage Regulator

Heater filament voltage is supplied by the 8-volt line and is re gulated by IC604. Heater on/off is used to turn the output on or off. This is found at pin 4, VC. The output is off during active off and suspend modes.

Feedback Circuit

The feed back circuit is divided into two sections. One is for active off and suspend modes, the other for active on mode. The following two sections explains the theory and operation.

Active Off and Suspend Mode Feedback

Feedback is provided by circuit elements IC603, D632, Q658 and Q656. The 16.5V line is regulated and the actual voltage is 8.7. Due to this condition, B+ is no longer regulated and is reduced approximately 67%.

During active off and suspend modes, remote on/off is low and Q656 is off. Current flows through D632 when the 16.5 V line is greater than 8.2 volts. This current biases Q658 and current from IC603 is allowed to sink to ground. The 16.5-volt line supplies this current to IC603. The current through IC603 biases its transistor and sinks current from IC601 pin 9. IC601 then responds accordingly and adjusts its duty cycle in order to make the output voltage reach 8.7 volts. This completes the feedback loop.

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+8V

IC604

PQ6RD83B

Heater

Regulator

Heater

ON/OFF

Feedback Circuits

IC605

TDA8138A

C623

Heater

out

D610

+8V

Q601

+5V BACK UP

R636

Q606

R635

R617

D618

R637

D619

C662

DISABLE

GND

R666

D607

C634 C635

OUTPUT 1

OUTPUT 2

+5V

REMOTE ON/OFF

+16V

Q607

R638

C636

When remote on/off is set high, Q656 is turned on and Q658 is turned off; this disables active off and suspend modes regulation loop.

Active On Mode Feedback

As stated earlier, when Q656 is on, the acti ve of f and suspend mode re gulation is disabled. At this time, IC652 takes o ver and the B+ line is regulated. IC652 is a shunt regulator and regulates the B+ voltage by sinking current from IC603 to ground. The reference voltage at pin 2 determines the sink current into pin 3. The reference voltage is set to 2.495 volts by resistor divider R659 and R660. Since the B+ is connected to the resistor divider, any changes in voltage is detected at the reference terminal; the shunt regulator then tries to force the reference voltage to 2.495 volts by sinking more or less current into pin 3. As mentioned before, IC603 biases its transistor accordingly and IC601 responds by changing the switching duty cycle in order to keep the output voltage at 183 volts. The other components connected to pins 2 and 3 are for compensating frequenc y response. This completes the feed back loop for active on mode.

4. Protection Circuits

There three protection circuits: OCP, O VP and secondary short circuits. OCP is pulse by pulse and is performed on the primary side. OVP detects e xcessive output voltages. To detect secondary side short circuits, there is a circuit called B+ detect and it is monitored by the microprocessor. The following will explain the operation of these functions.

OCP

OCP is activated if there is too much current passing through the power MOSFET, Q602. This condition will occur if either the B+ line or 80 volt line is shorted.

R609 is the current sense resistor. Current through this resistor will cause a negative voltage drop in reference to ground. R608, R606 and C615 couples this voltage drop to IC601 pin 4. If the voltage level exceeds –0.18 volts, the IC sets pulse by pulse current limit and the output voltages are in affect very low. This condition is often audible and characterized by a ‘chirping’ sound.

OVP

The function of OVP is related to IC601 and the threshold is approximately 19.4 volts. This is sensed at pin 7 of IC601. Under

- 6 -

normal operation, the VCC voltage is 17.5 v olts. In the e vent the re gulation loop was open or the control loop fails, the outp ut voltages would rise rapidly. Likewise VCC will rise and when the threshold voltage is reached, IC601 would latch up. This condition disables the output circuit at pin 6 and the power supply will not operate. Since the IC is now latched, only turning the AC switch off and then on again can restart the power supply.

5. Secondary Short Circuit

B+ detect purpose is for determining secondary side short circuits. Sensing the node voltage of resistor divider R611 and R612 does this. R611 is connected to +5V and –16.5 is connected to R612. If the node voltage exceeds 2.0 volts, the microprocessor sets PWR Shut Down to digital high. In this event, Q657 is turned on and feedback current is bypassed to ground from IC603. This causes unregulation and the output voltages become high. The VCC winding on the primary side reflects this condition and exceeds 19.4 volts, which will cause IC601 to latch and disable the power supply. Turning the AC switch off and then on again can only restart the power supply.

An additional short circuit protect is provided if the +12V, +5 or 3.3V lines are shorted. This is through circuit elements D641, Q640 and Q657. During normal operation, through D641, the +5 volt line biases Q640 on. The 80 volt line is connected to the collector of this transistor through R641. When the transistor is on, the collector voltage is nearly zero. This point is connected to Q657 through R642 and Q657 is still off. If there is a short on any of the lower voltage lines, the +5 volt line will become lower than 3 volts and Q640 will turn off. In this case the collector voltage rises and Q657 will turn on. Then through Q657 the feedback loop current is shorted to ground and causes OVP, which is sensed by IC601.

TO IC601

Pin 2

Q658

2SC3311A

ISS119

IC606

PC123FY2

TO IC601

Pin 9

D631

IC603

PC123FY2

FEED BACK

Q658

2SC311A

ACTIVE OFF

REGULATOR

Protection Circuits

Q605

DTC124ESA

IC652

TL431BCLPRA

Remote ON/OFF

16V

Remote ON/OFF

180V

Power shut down

Q657

DTC124ESA

OVP

D640

1SS119

C640

2200p

R642

10K

80V

Short circuit

Protection

Q640

DTC124ES

- 7 -

6. Troubleshooting

Warning

Before attempting to fix the power supply, safety should be consider first. Never connect test probes to the primary side circuits, unless proper isolation has been installed. If isolation for the AC mains is not present, serious harm can occur . Never assume you are safe.

No Power

In the event that the monitor does not turn on, first check F601 and R615. If these parts are blown, the primary side circuitry should be checked. If the fuses are not blown, then check the secondary side circuitry, especially the protection circuits. If these circuits are causing a no power symptom, the problem can be more readily found.

AC Input and Degauss Circuit Trouble Shooting

For no power or nonoperating power supply, the AC input circuitry should be checked. Open or short circuit elements will cause non-operation. F601, CN600, CN603 and CN2003 On the H Board should be checked first. The wiring between the AC switch on the H Board and D Board should be checked. Check the front panel AC switch for continuity.

If all elements are correct, check whether F601 breaks when power is applied and the AC switch is closed. If the fuse does blow, there may be problems with the primary circuitry or a component short.

The degauss will malfunction if CN601 is not connected. One problem could be loss of degauss signal from N Board. This can be verified by using the manual degauss command found in the OSD menu. If the signal does not appear at R670, then check the signal on the N Board and all connections. It is possible that the microprocessor does not function correctly .

The second step is to place a short across the AC terminals of RY601 for less than two seconds. If degauss operates then check Q670 and RY601. If degauss does not work, check THP602 for an open condition and VA601 for a short condition.

Primary Section

Three main areas can diagnose primary circuit failures. These are IC601, Q602 and Feedback system. Visible checks of these areas will aid in finding problems. The following will discuss each section.

IC601

First apply AC to the monitor and check IC601 pin 6 output. If the output on pin 6 is not present or briefly appears, there could be problems with Q602 and related parts. Further, check VCC level at pin 7. If it less than 9 volts, the IC could be in latch mode. If the voltage is very low, there could be a short on any of the IC pins. In reference to ground check the impedance of pin 1, 6, 7 and 9. If any of these pins are shorted, replace the IC and check components connected to the related pins. Pin 1 is especially vulnerable to damage. Take care that C619 and C616 are fully discharged before replacing the IC.

Q602

The switching transistor can be damaged in various ways. These are related to voltage, current and temperature.

Check whether the transistor is shorted across drain and source terminals. If there is a short, R609, R615 and FS601 should be checked. R609 is usually broken when Q602 fails. Additional components to check are D603, D604 and IC601. If Q602 is shorted, all these parts should be replaced.

Failure of a secondary rectifier diode can also cause Q602 to fail. Check B+ and 80V diodes for open or short conditions. There is also a clamp circuit, which is used to clip the turn off spike found on Q602 drain. If the clamp circuit is broken, it can cause Q602 failures. Check D615, C622 and R619.

Secondary Circuit

Failure in the secondary circuits can be categorized by rectifier diodes, fusible resistors, regulators, +5 volt back up circuit, feedback loops and protection circuits. These sections are interrelated and failure in one can af fect another. Consequently, some failures will also affect the primary circuitry.

Rectifier Section

Rectifier diode failures are not common, but do occur. Deflection, video and N Board failures contribute to diode damage. In the event a voltage is not present, check for shorts to ground, open or short diodes. Also check fusible resistors or any zener diodes found on the voltage lines.

- 8 -

Horizontal Centering

Loss of horizontal center adjustment can be affected by the rectifier diodes, fusible resistors, IC502 and related circuitry. Measure the voltages in reference to the horizontal centering ground. Typically, the voltages are ±8 volts. However, the adjustment setting can reduce the voltages by 1 volt. If there are no problems found with the diodes or fusible resistors, the next step is to check the adjustment signal at Q517. If the adjustment signal is not present check the N Board and connections. Otherwise, check IC502 and related components.

+5/12 Volt Regulator

Loss of voltage due to shorts or device failures on either +5 or +12 volt output lines can occur. Consequently, IC605 can be damaged and need replacing. Before replacing IC605 check for shorts or damaged parts along the output lines. If +12 volt does not appear, check the remote on/off signal. The N Board supplies this signal and it may be necessary to check it and all connections.

+5 Volt Standby Circuit

Failure of this circuit can be affected by IC605. The remote on/off signal controls circuit operation and it may need checking. In case the circuit does not work properly, check D619, R617 and Q601. If these components are good, check the remaining circuit parts.

Heater Voltage Regulator

This circuit may be affected directly by fusible resistor R654 or D654. If these parts are good, check the regulator output for a short to ground. Shorts can occur on the video board. In the case of an output short, IC604 may have been damaged. If the IC appears to have no damage, check the connections and N Board for any problems with the heater on/off signal.

Feedback Circuit

Problems with feed back can cause power supply shut down or low voltages. First determine whether the power supply is operating in active off, active on modes or not at all.

The power supply can be stuck in active off mode. The remote on/off signal, Q656 and IC603 can affect this condition. Likewise, if the power supply is always in active on mode, the same items should be checked.

Checking for voltages at IC603 pins 1 and 2, IC652 pins 2 and 3 can solve more difficult problems. Additionally, IC603 pin 4 and IC601 pin 9 should be checked. If there are problems with these devices, B+ or 16.5 volt line, the feedback systems will not work correctly. Also check the protection circuits.

Protection Circuits

OCP occurs when there is excessive current through Q602. Failures with Q504, Q505 or the video section commonly cause this condition. These areas should be checked. OCP condition can also occur if R609 is open or if there are problems with IC606 or Q605.

OVP usually occurs when the feedback loop is open, secondary voltage shorts or loss of +5 volts. Isolate the OVP trigger condition, by first checking the operation of the feedback loop and Q657. Either PWR shutdown or Q640 can turn on Q657. The feedback loop can be verified by removing Q657 and measuring the B+ voltage level.

- 9 -

D BOARD DEFLECTION SECTION

1. Horizontal Deflection Circuit

Overview

These circuit drive the DY(Deflection Yoke) for Horizontal Deflection. The H size and H shape control (IC805 and around) is included in this page as well.

H Drive, H Out, Feedback

HD pulse supplied from N board is inverted by Q501 and switch Q504 through Q502,503. The drive current which introduced in HDT by this switching will drive Q505(H OUT) and 1000v pulse appears on collector. D504 is the “Damper Diode” which avoid the negative pulse and discharge the energy for next Horizontal Drive. Q514 is the buffer for the “H FBP” feed back to N board and it will be the reference of phase/jitter control of DSP. T504( HST) is to sense the deflection current going to DY. The voltage appeared on secondary side will be the feed back for H Size/Shape control.

H Size/Shape control

HD pulse also triggering the H Size/Shape control IC805 (pin#8). IC805 is “PWM IC” and it controls H and HV B+ chopper duty. H Shape coming from N board is already including the Size Information(DC Level). It will be supplied to IC805 (pin#2) after pulled up to 12V through R813. H Reg Output(pin#20) is switching pulse of Q506(B+ chopper). The energy supplement from 180v to H Def circuit (through T502) is controlled by the duty of this pulse. The H Shape input and feedback voltage(pin#20) from T504 are compared by error amp (in IC805) and H Reg out pulse duty is controlled to keep the level of these two the same.

T roubleshooting

See attached “FLOW CHART” and confirm if it’s really H Deflection issue.

No H Deflection / No Power

Check Q505, Q506 and D504 first. In case any of these shorted, check T501, Q504, R507 and D502. Those parts might have been damaged. If both of Q505, 506 were not broken, check the HD pulse at the gate of Q504. If no pulse, check Q502, Q503, Q504. Otherwise, check R512, D503 or try changing IC801.

Bad Distortion

Check pin#2 of IC805 and confirm that proper DC level and AC waveform. If the distortion is on only right side, check all above (“No H Deflection”). Otherwise, refer to the Troubleshooting of next section (“H Lin and Ringing Correction”).

- 10 -

H Deflection Circuit

R517

R518

320

H DefINH Reg

Out

PWM IC805

H SHAPE

12V

2 7

H SHAPEINHD

R512

- 11 -

R813

D503

D505

180V

L501

Q506

B+CHOP

Q518

12V

TO:

H Lin and

Ringing Circui t

HDYHDY-

CN801

HD out

T501 HDT

12V

Q502

Q501

Q504

D502

T502 HOC

D504

C507

T504

HST

Q514

H DY+

H FBP

TO CN801

#32

Q505

Q503

H-OUT

R507

-16V

2. H Linearity and Raster/Distortion Ringing Correction Circuit

This section includes HLC Control circuit which is new in D98, S cap switching and HLC/S-Cap Damping circuits. These circuits are placed directly on the “cool side” of DY which is in series with deflection current line. H Centering circuit will be explained in next section.

HLC Balance Control and HLC damping

There is no HLC switch for this chassis. Instead of that, HLC(L502) effectiveness is changed by LCT(503) for each Fh since T503 and L502 is in parallel. LCT is Cross Transformer which can change its inductance accordingly to the DC current of secondly side. The current of secondly side controlled by DAC output of MICRO through Q507. *It can be changed by register “HLC BAL”. R520 and C528 is damping circuit to avoid the Raster Ringing (mainly on left side of picture) caused by HLC, DY and S-caps.

S-Cap switching and S-cap Damping

H Def current is distorted by resonance between S-Cap and DY to correct the linearity. Since the resonance frequency has to be changed for each fH, S-Cap switching is controlled by MICRO Switches are "On" when its gate is Hi(5V) and that moment, drain voltage should be grounded (0V).

L505, R522 and C513 is damping circuit to avoid Distortion Ringing (mainly on top of the picture) caused by S-caps and H Control loop gain. L504, R523 and C527 is also the same purpose as above but only works when Q508 (Switch for the Biggest S-Cap) is “On”.

Troubleshooting

See attached “FLOW CHART” and confirm if it’s really H lin issue.

Bad Linearity

Confirm that Raster is approximately in the center of the Bezel. If not, refer to next section (Raster Centering Circuit). Check S-cap switches (Q508, 509, 510, 511, 512, 513) and confirm that H Linearity changes proportional to the value of “S-Cap Direct”. Confirm that H LIN BAL changes by the register value of ”HLC Balance(Max/Min)”. If it’s not working, check Q507 and the connection between N bd and D bd or, Check L502, T503.

Bad Top Distortion/ Left side Raster Ringing

Check damping circuits explained above or check the connection between N & D(HLC control line).

3. H. Raster Centering Circuit

Overview

H Centering is changed by supplying DC current to DY. D98 is taking the common level on DY cool(-) side and +/- 8V from power supply transformer(T601 PIN#10, 11, 12. #11 is the common).

H Center Circuit

The DC current is outputted by powered OP-amp(IC502). This circuit is making “invert amp” with the gain of R549/R548 and input 1S Q515 collector. The level is controlled by MICRO”H CENT’ through Q517(buffer). Q516 is Stand by-MUTE switch which activates when “Remote On/Off’ is Off(Lo).

Trouble Shooting

See attached “FLOW CHART” and confirm if it’s really H Center Circuit issue.

No Raster Centering Control

Check R621, 622(Right next the SRT) first. If it’s open, change IC502. Confirm that voltage of Q5 l 5 base is changing accordingly to “H CENT MAX or MIN” register. If not, change Q517 or check the connection between N and D. Confirm that Q516 is Off. This circuit should not work when the Monitor is in Main mode. Check IC502.

CAUTION!!

The heatsink of IC502 is connected to the H center(-) level, not GND! It could have up to 150V and should not be touched to any other metals.

- 12 -

H. DEFLECTION

CIRCUIT

H DY+ H DY+

H DY-

R520

C528

100

330p

2kV

:RS

TO H. CENTERING CIRCUIT

2SK2098

R527

47k

4 S

Q509

C517

0.01

C518

0.68 250V

:PP

:PT

C521C522

R530

0.068 250V

:PP

Q512Q513

47k

IRLI530GIRLI530G

0.01 :PT

1 S

- 13 -

0.033 400V

:PP

C526

0.01

:PT

0 S

R529

2 S

0.15 250V

:PP

47k

C524C525

0.01 :PT

C519C520

0.33 250V

:PP

Q510Q511

IRLI530GIRLI530G

R528

47k

C523

0.01 :PT

3 S

R525

C515

L504

1.5 10mH

250V

:PP

47k

R543

47k

R536

SSSSSS

C516

Q508

2SK2098

:PT

5 S

R523

1/2W

:FPRD

C527

4.7

250V

C514

0.17 400V

:FPRD

C513

2.2

250V

T503 :LCT

Q507

2SC2785-HFE

HLC CTRL

L505

2.2mH

R522

1/2W

2 1

R526

:RN

L502 :HLC

C537

0.22 :MPS C511

0.22 :MPS

R519

2.2k

R747

L A B

N I L

. H

C512

:FPRD

16V

H DY-

BOARD

H. LINEARITY AND RASTER/DISTORTION RINGING CORRECTION CIRCUIT

FROM D648 IN P.S.

C656

HC+

R547

C538R545

R549

HC+

IC502

R546

TO H. DY(+) VIA T50

L503

(DRAIN OF Q506)

R541

HC-

!!!

IMPORTANT !!!

TO H. DY(-) VIA L50

R551

HC N

HC-

C545

Q515

D511

R550

R548

R542

Q516

STBY SW

R552

FROM PIN# 11 T601

FROM D649 IN A.S.

C657

Q517

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H. CENT

R815

16V

REMOTE ON/OFF

Q802

CENTER VOLTAGE

COMMON

(ISOLATED)

(BOARD)

(19D98 H. CENTERING CIRCUIT)

Rotation/Vertical Key Circuit

+5V

R735

Rotation Coil(CN702)

R775

R708

R709

C701

R707

C702

IC702

+16V

-16V

V+

V-

R736

R737

R729

C705

N-BOARD

D.TILT

IC1002(DSP)

ROTATION

IC1001

4. Rotation/Vertical Key Circuitry Mounted on the D/N Boards) Circuit

Theory of Operation

The Rotation/Vertical Key circuitry takes its input from the N-board via pins 40 (Rotation) and 42 (D.Tilt). D. (Dynamic) TILT is generated by the DSP (IC1002) while Rotation is generated by the microprocessor (IC1001). Rotation is a PWM waveform at approximately 40kHZ measuring 5V pk-pk at pin #3 of the microprocessor. While D.TILT is a triangular waveform at the vertical scan rate, 1.0Vpk-pk in amplitude centered at 1.5V. Typical waveform patterns are provided as figures #1 and #2 below. Rotation is filtered by the R729 and C705 combination and a DC offset is added to D.TILT from the +5V line via R735. These two waveforms are added together and amplified by IC702. This amplifier is a transconductance amplifier (it amplifies a low-level voltage into a high level current). The output current from pin 4 of IC702 flows through R709 and the rotation coil and returns to ground through R708. The feedback is sensed at R708 and sent back to the amplifier through R707. The DC level of the current through R708 is controlled by the Rotation signal while the triangular currant amplitude is controlled by the D.TILT waveform.

FIGURE 1 FIGURE 2

T1 21.60us

T2 150ns

DT 21.75us

T1 1.10ms T2 2.60ms

DT 13.70ms

Vertical Key Circuit Troubleshooting Hints

It is possible to have a malfunction of only the Vertical Key portion of the circuit. This can occur by a loss of signal from D.TILT. First check if the Rotation function is working properly. There should be no more them a +/-15 degree picture rotation by operating the rotation function through min-max extremes. When the Rotation function is at its full position (SV at R729) the voltage at R708 should be a positive 2.25 vdc, approximately. And at its full negative position this voltage should be a negative (-) 2.5 vdc approximately (NOTE: if D.TILT is open or shorted to ground these voltages will not be well centered around 0V).

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Signal tracing should begin at pin 59 of IC1002 on the N board. The triangular output waveform at this point should change +/-1 vdc by operating V.TrapSawBtm and V.TrapSawTop registers through function through min-max extremes. This same signal should appear at pin 42 of CN801 and at the input side of R736. Screen movement for this function is as shown below:

1.5mm

V.TRAPTOP

(Dashed lines Indicate

Negative movement)

Movement

V.TRAPBTM

(Dashed lines Indicate

Negative movement)

Movement

Rotation Circuit Troubleshooting Hints

If Rotation does not work Vertical Key will not work. Signal tracing for a rotation problem can start at pin 3 of IC1001. The Rotation signal will be a square waveform at 40kHz. This signal is filtered at the R729, C705 combination. If this waveform is reaching R705 the problem is in the IC702 area.

5. Dynamic Focus Circuit

Overview

Both H and V Dynamic Focus Waveform originally formed by DSP. H DF is amplified by Hi-speed OP Amp and also Transformer. V DF is amplified by Transistor inverter.

H DF

IC703 is amplifying the H DF waveform formed by DSP. The voltage is re-amplified by T701 to about 600Vp-p and supplied to FBT.

V DF

V DF waveform is buffered by Q707 and amplified by Q706 to about 200vp-p. 300v Vcc is made by FBT through D906. This voltage is also used for HV Protector.

Troubleshooting

See attached “FLOW CHART” and confirm if it is really a DF issue.

Bad H DF

Confirm that waveform from N board is correctly there(1Vp-p). Check the voltage of pin#6 of IC703. If no output, change IC703. If there is wave form, change T701.

Bad V DF

Confirm that waveform from N board is around 3Vp-p. If it’s more than 3.3Vp-p, change the N board. Check 300v from FBT.

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Dynamic Focus Circuit

+16V

H. DF FROM N BOARD

C707

V. DF FROM N BOARD

R723

Q706

R724

R734

H. DF TO FBT

PIN# 14 VIA R9

T701 :DFT

R742

V. DF TO FBT

PIN# 15 VIA R909

C711

C714

R733

R738

C728

R754

D905

R917

+16V

IC703

-16V

300V

C931

R727

Q707

6. High Voltage Protect Circuit

This circuit generates the High Voltage supply for the anode and G2 (1000V) of the CRT. It consists of a high voltage driver and regulator similar to a switching power supply function. In addition, there are High Voltage and Beam Current protection circuits. All those circuits are similar to N3 or D1 chassis circuits.

High Voltage Regulation and Output Circuit

The HV Drive pulse is generated by IC805 and synchronized with Horizontal drive pulse. It is supplied to the Gate of Q902 the HV Out FET .

The HV Out Pulse approximately 700V, is generated by Q902 switching with the peak voltage being controlled by the switching duty of Q901 (B+ chopper). Internal resistors and R903 and RV904 divide HV generated in the FBT. Since this voltage is the feedback for HV Regulation control. Adjusting RV904 will result in changing the HV Regulation level(= HV level). HV Feedback voltage is returned to IC805 at pin#12 to be compared with an internal reference voltage of IC805 at pin#13. According to this feedback level, IC805 changes the pulse duty cycle. This pulse is felt at pin #18 of IC805 thereby controlling the output of B+ chopper drive Q901.

G2 Voltage

G2 voltage at approximately 1000vdc is produced by the FBT rectifying the output voltage of T901 pin#2 through D906 and C933. This voltage will be supplied to A board via CN 510, which contains the G2 control circuit.

HV Protect Circuit

HV Protect circuit will be activated by the Microprocessor when the signal at HV DET, CN801 pins#24 reaches a +5vdc level. HV DET indicates the level of the primary current developed by the 300V winding of the FBT through R921, D908.

Beam Current Protect

Beam Current Protect will be activated when ABL DET at CN801 pin#1 reaches a level of 0V when operating in main mode. ABL DET level is corresponding to the Beam Current which is supplied to FBT through R914 and D909. The voltage current relationship is inversely proportional Volta ge (down) Current (up).

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