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JVC AV-27MF36 Power Supply Training
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JVC AV-27MF36 Power Supply Training

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JVC Television
Power Supply Training

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Summary of Contents for JVC AV-27MF36

  • Page 1 JVC Television Power Supply Training...
  • Page 2 If you need more information on Computer and Electronic Repair, please visit these websites to improve yourself. http://www.fastrepairguide.com http://www.protech2u.com http://www.plasma-television-repair.com http://www.lcd-television-repair.com Happy Repairing!! Highly Recommended Repair Ebook: If you’re a LCD Monitor repairer, then this is the best guide for you. Why? Because, the author revealed all his LCD Monitor Repairing secrets for you.
  • Page 3 TELEVISION INTRODUCTION After this course, you will learn: • The operation of Switching supplies • Details about the regulator IC • Operation of the Power Supply Modes • The operation of the Power Factor Circuit • Troubleshooting procedures useful in diagnosing defective components •...
  • Page 4 TELEVISION AGENDA • Model Identification • Service Manual Supplements • Switching Power Supply • Power Supply Components • Basic Switching • Switching Device • Switching Operation • Switching Review • Power Factor circuit • Troubleshooting techniques...
  • Page 5 TELEVISION MODEL IDENTIFICATION...
  • Page 6 • Prior to service, it is always wise to verify the Model and Version to ensure that the correct Service manuals and Schematics are being used. • In some cases, the Version may indicate PWB or CRT differences • This information is listed in the Main Difference List of the Service Manual, or the Service Manual Supplements.
  • Page 7 TELEVISION SERVICE MANUAL SUPPLEMENTS Original Service Manual Service Manual Supplement Supplements show Corrections, Additions and Differences that may have occurred during the production of a TV Model. No. YA318B 2006/6 Picture tube of AV-48P776/H was changed. Therefore, this service manual describes only the items which differ from those of the AV-48P776/H service manual. For details other than those described in this manual, please refer to the AV-48P776/H service manual (No.YA318, 2005/11).
  • Page 8 • Some Service Manual have Supplements • Supplements show Corrections, Additions and Differences that may have occurred during the production of a TV Model. • It is necessary to ensure you have all Service Documents for a model prior to servicing. •...
  • Page 9 TELEVISION SWITCHING POWER SUPPLY When troubleshooting it is necessary to use the respective ground of the device you are measuring. LIVE ISOLATED Taken from Schematic 52004 Main PWB...
  • Page 10 • This is the Power Section from the AV-32F703 taken from the 52004 Schematic of the Main PWB. • On the schematic, there a BLACK line that separates the LIVE and ISOLATED sides of the PWB. Components on the left side are live. Those on the right side are isolated •...
  • Page 11 TELEVISION POWER SUPPLY COMPONENTS 1. F901 and VA901 Surge Protection 2. T951, D954-57 and C951 Standby Power 3. C901, C902 and C903 Line Filter: 4. D901 and C907 Main rectifier 5. IC911 Switching Regulator Startup 6. D911, R911,R930 and C914 7.
  • Page 12 This is a brief explanation of the components that make up the Power Supply and there functions. • This is the basic circuit configuration and use for all JVC Power Supplies. While some Power Supplies may omit or add circuits, the general function of all JVC Power Supplies are the same.
  • Page 13 TELEVISION BASIC SWITCHING INDUCTOR CHARGING 1. Switch SW1 off 2. Apply a DC to the inductor as shown 3. Turn SW1 on and the Current rises slowly 4. The Inductor charges to its maximum 5. After charging is complete, the current stays constant...
  • Page 14 • One of the important part in SMPS is the Transformer. Transformer functions like a basic inductor. • With a DC applied to an inductor and connected to ground through a resistor, if the switch is turned on, the current will rise slowly through the inductor and the resistor.
  • Page 15 TELEVISION BASIC SWITCHING INDUCTOR DISCHARGING Once the Inductor is finished charging, turn SW1 off. 1. What happens to the charge in the inductor? It will be lost as heat. 2. Can we use this energy? If so, how? 3. Can we control this charging? If so, how? This can be applied in the Switching Power supply.
  • Page 16 • When the current flow to the Fully Charged Inductor is interrupted by closing SW1, the stored energy is released as Heat. • This stored energy is utilized in the Switching Power Supply.
  • Page 17 TELEVISION BASIC SWITCHING TRANSFORMER OPERATION ENERGY If there is a secondary winding during the off time, energy will be transferred into the secondary. In other words: Transformer charges during ON-time. Discharges during OFF-time...
  • Page 18 If the coil has a secondary winding and a load is attached, it is called a transformer because it transforms the energy into electrical energy and delivers it to a load. In other words, the transformer discharges its stored energy into the secondary. Repeating these actions again.
  • Page 19 TELEVISION BASIC SWITCHING SUMMARY Apply an unregulated DC Voltage to the Transformer’s Primary. Switching the Primary ON and OFF will result in Secondary Voltage. Controlling the ON/OFF timing of the Switching Device will result in a Regulated Secondary Voltage Switching power supply regulation is achieved by controlling the switching device’s ON/OFF timing .
  • Page 20 TELEVISION SWITCHING DEVICE • STR-Fxxxx IC • Very reliable construction • All in one package O VP • Protection circuits • Minimum pins (5 pins) STR- Ocp/ F6xxxx...
  • Page 21 • It has the actual ON/OFF switch (a Power FET), control circuits, and protection circuits. The Internal Circuits of the other Switching Devices used by JVC may vary, but the operation of the Device is the basically the same for them all.
  • Page 22 TELEVISION SWITCHING DEVICE Properties V IN • 0.7V Applied to Pin 1 will turn OFF the FET Start Up Latch • FET will turn on after pre-determined time Pre Reg OCP/FB • Applying a 2.0V pulse to Ref1 Osc. T.S.D Pin 1 refreshes the IC prior to pre-determined Ref2...
  • Page 23 • When a Start up DC is applied to the other circuits inside the IC, it turns the FET ON. • When the FET is ON there will be a short between pin2 and pin3 of the IC. • If 0.7V is applied at pin 1, the FET turns OFF. Due to the internal timing circuit, the FET will start again after a pre-determined time.
  • Page 24 TELEVISION SWITCHING DEVICE Internal V IN Start Up Latch Pre Reg OCP/FB Ref1 Osc. T.S.D Ref2...
  • Page 25 Startup: When we apply approximately 12V to pin4, the IC’s internal circuit functions and turns ON the FET Drive: When the internal circuit is turned on, the driver circuit turns ON the power FET Power FET: This is what we previously called the Switch. We use this to allow current to flow through the transformer.
  • Page 26 TELEVISION SWITCHING DEVICE Turn ON D901 • Apply power to the IC • When the tank Capacitor charges up to the D911 Start-up voltage, IC starts conduction R911/ R930 • The Switching FET turns ON C914 • Now it can switch the RAW-DC through the Transistor, if it is connected D901 Reference Schematic 52004 Main PWB for Schematic Details.
  • Page 27 • This is start up circuit. This circuit composes R911, R930, D911 and C914. •This circuit Provides the Start-up Voltage for the Switching IC911 •The DC voltage supplied by this circuit turns the IC and FET ON. •If the IC was open and AC current was allowed to flow, no current would flow through the IC.
  • Page 28 TELEVISION SWITCHING DEVICE TRANSFORMER CHARGING C907 T921 • Current flows through the transformer and charges it • A proportional voltage develops at the source resistor • Turning the FET off will cause the switching action R912 R913 Reference Schematic 52004 Main PWB for Schematic Details.
  • Page 29 • Once the startup DC is applied, the FET can turn ON • The Transformer is allowed to charge. • Raw DC is passed through the primary of a transformer to the IC pin 3 • The Voltage passed through the FET connects to a source resistor on pin2 to ground.
  • Page 30 TELEVISION SWITCHING DEVICE Turn Off V IN • Applying 0.7V to Pin 1 will turn OFF the FET Start Up Latch Pre Reg OCP/FB Ref1 Osc. • FET will turn on after T.S.D pre-determined time Ref2 Do you remember this?
  • Page 31 If 0.7V is applied at pin 1, the FET turns OFF. Due to the internal timing circuit, the FET will start again after a pre-determined time.
  • Page 32 TELEVISION SWITCHING DEVICE Turn Off • When the FET conducts, a ramp voltage is generated at pin 2. • We use this ramp to turn FET off and hence create a R914 switching action C913 Ramping Voltage builds here and is feed back to pin1. If this feedback Resistor/Capacitor opens up, the IC will never be turned off.
  • Page 33 • We already discussed that the IC is designed such that if we apply 0.7V at pin1, it will turn off the IC temporarily. • The circuit is designed in such a way that when the transformer is charged, 0.7V builds at the Capacitor C913. •...
  • Page 34 TELEVISION SWITCHING DEVICE SECONDARY VOLTAGES • Repeating ON/OFF switching generates Secondary Voltages • IC function drains the ICs Power Supply and it becomes too low The IC could Shut OFF due to insufficient Supply Voltage Reference Schematic 52004 Main PWB for Schematic Details.
  • Page 35 • When DC is applied to pin3, current will flow through the transformer and charges it. The current will generate .7 V on pin2. This is applied to pin1 to turn it off. • When the Inductor shuts off, the Inductor discharges the energy to the secondary.
  • Page 36 TELEVISION SWITCHING DEVICE SUPPLEMENT POWER (RUN-DC) • Supplement the start-up DC with Run-DC • IC Power Supply becomes stable D912 R915 • Transformer fully Charges/Discharges Reference Schematic 52004 Main PWB for Schematic Details.
  • Page 37 From the generated secondary voltage, an additional DC is supplemented using a Resistor and Diode. This is known as Run-DC circuit Now that the supply is steady and running, We have secondary voltages. The Transformer charges fully and discharges into secondary...
  • Page 38 • Standby Mode used when TV Off. Reference Schematic YA321 Power and Def PWB for Schematic Details There are 2 general types of circuit configurations used in JVC Power Supplies. TYPE 2 - POWER ON • Switching Circuits ONLY supply Power after TV Power is ON.
  • Page 39 There are 2 general types of circuit configurations used in JVC Power Supplies. TYPE 1 - ALWAYS ON •Utilizes a Standby Mode when TV Power is OFF. •Standby Voltage for Micon is supplied by Switching Circuits. •Example shown that T2921 supplies voltage to the DC Regulator (IC2922).
  • Page 40 TELEVISION SWITCHING OPERATION STANDYBY MODE • In Standby Mode, very few devices are functional • They need only very little charge • We must reduce energy transfer...
  • Page 41 • Some units utilize a Standby Mode. •In Standby Mode, very few devices such as CPU, memory, etc. are functional. • Since CPU power is also provided from the transformer’s output, we can not turn off the regulator. • In order to minimize the Power consumption, we control the energy transfer by reducing the charging and discharging time.
  • Page 42 TELEVISION SWITCHING OPERATION STANDBY MODE GRAPHIC Standby On-tim e Additional Norm al On-tim e Standby • In normal mode, the on- Turn off by Feedback time is the transformer’s charging time • In standby mode, additional DC added to the ramp Turn on by •...
  • Page 43 • In normal operating mode, the ramp size depends on how long it takes the current to generate the 0.7V Ramp. • By this time, the transformer would normally be fully charged. • In standby, we don’t need the transformer to charge fully, this means reducing the ICs on-time.
  • Page 44 TELEVISION SWITCHING OPERATION ADDITIONAL DC USING PHOTO COUPLER • Additional DC is applied from IC’s supply using a Photo Coupler. • The Photo Coupler must be turned On in Standby Mode and turned Off in Normal Mode...
  • Page 45 In the Standby Mode, additional DC is provided from the ICs Supply Voltage using the Photo Coupler. The CPU’s outputs a High turning the Photo Coupler on. The Photo Coupler supplies additional FeedBack DC to pin1. As we already saw in the chart, this must be added in standby and must be removed in normal mode.

  • Page 46: Table Of Contents

    TELEVISION SWITCHING OPERATION SUPPLEMENT POWER (RUN-DC) AC In •During Standby Mode, the Run DC may be insufficient to keep Switching IC ON •IC Power is supplemented by Regulated Voltage 1STB13 STR- F6514/5 Ocp/...
  • Page 47 • When power is turned on, the Run-DC is sufficient to keep the IC functioning. • During Standby Mode the Output Voltages from the Transformer is reduced. • When this happens, the IC could turn off due to the insufficient Run-DC Voltage that is being supplied. •...
  • Page 48 TELEVISION SWITCHING OPERATION PHOTO COUPLER DURING POWER ON Relay AC In • At Power On Micon outputs LOW 1STB13 • Photo coupler is inactive • On-Time is normal 1STB13 STR- F6514/5 Ocp/ • B1 relay is turned On...
  • Page 49 • At Power-on, Micon’s power control output goes low. • This signal (through some inverters) turns on the relay and supplies power to Main Power output. • At the same time, the Micon turns off the Photo Coupler. The control circuits for the Photo Coupler and their operation may vary slightly in some models...
  • Page 50 TELEVISION SWITCHING OPERATION ERROR AMP Relay • Error amp monitors AC In • Controls Photo 1STB13 Coupler to Reduce on-time if B1 exceeds spec STR- F6514/5 Ocp/ Error Amp...
  • Page 51 • When the on-time is normal sufficient energy is transferred and the B1 supply; High voltage, etc.. is active. • If the B1 Supply is more than required, it must be reduced. • By controlling the ON/OFF timing of the supply, the B1 Supply voltage can be controlled.
  • Page 52 TELEVISION SWITCHING OPERATION REFRESH • In practical use, we need to restart the IC earlier than the AC In pre-determined time • Apply 2.0V pulse to pin1 • During the negative edge, the IC will refresh (reset) and turns on again. Refresh Ocp/ G en.
  • Page 53 •When the transistor is off the ramp voltage will disappear because of the internal oscillator. •After a pre-determined time, the FET will turn on again. •In case of additional power requirements by the TV circuits, instead of waiting for the internal Timing generator to turn on the IC, we can refresh the IC.
  • Page 54 TELEVISION SWITCH CIRCUIT REVIEW POWER SUPPLY COMPONENTS 1. F901 and VA901 Surge Protection 2. T951, D954-57 and C951 Standby Power 3. C901, C902 and C903 Line Filter: 4. D901 and C907 Main rectifier 5. IC911 Switching Regulator Startup 6. D911, R911,R930 and C914 7.
  • Page 55 IC921 Error Amp: Monitors B1 Line Voltage This is the basic circuit configuration and use for all JVC Power Supplies. While some Power Supplies may omit or add circuits, the general function of all JVC Power Supplies are the same.
  • Page 56 TELEVISION SWITCH CIRCUIT REVIEW We will quickly go through the operation of a Switching Supply...

  • Page 57: Gnd Tsd Vcc

    TELEVISION SWITCH CIRCUIT REVIEW BRIDGE RECTIFIER AC In The AC line Voltage is converted to DC by the Bridge and Capacitor. STR- F6514/5 Ocp/...
  • Page 58 • The circuit begins with the AC Input, Line Filters (not shown), Bridge Rectifier and the Filter Capacitor. • The Bridge Rectifier converts the AC input into a DC output. • The DC output is stored by the Capacitor.
  • Page 59 TELEVISION SWITCH CIRCUIT REVIEW APPLIED DC A C In O VP Raw DC flows through the G N D T S D transformer to the Switching Device. VC C O SC D R V When the FET is turned On, it will allow current flow to ground.
  • Page 60 •DC voltage flows through the Transformer to the to FET. •When the Switching Device is turned ON, the FET will close. •When the FET closes it will allow the DC voltage to be ground through the Resistor.
  • Page 61 TELEVISION SWITCH CIRCUIT REVIEW RAMPING VOLTAGE A C In O VP G N D T SD V C C O SC D R V •Start-up Voltage applied to IC turns On FET, allowing current through Inductor. ST R- F6514/5 O cp/ •Current Flow allows the Inductor to charge and a Ramp Voltage to Build at IC.
  • Page 62 The Start-up DC is applied to the ICs Pin4 from the Bridge Rectifier through the Resistor and Diode. Powering up the IC turns On the FET allowing the DC voltage from the Transformer to pass through the FET. The current flowing through the Transformer allows the inductor to charge.

  • Page 63: Str- F6514/5

    TELEVISION SWITCH CIRCUIT REVIEW RAMP VOLTAGE FEEDBACK AC In •The ramp voltage is applied to pin1. •When the ramp voltage reaches 0.7V the FET will shut off. STR- F6514/5 Ocp/...
  • Page 64 • When the Inductor is charged, it is necessary to turn Off the FET to allow the Inductor’s stored energy to be released. • The Feedback of the Ramping Voltage through the Resistor connecting pins 2 and 1 will turn OFF the FET when the ramping voltage reaches 0.7V.
  • Page 65 TELEVISION SWITCH CIRCUIT REVIEW RUN-DC AC In 1STB13 •Transformer discharges into the Secondary when FET shuts off. •DC Voltage supplying the Switching IC STR- becomes insufficient. F6514/5 Ocp/ • Run-DC provided to IC from the Transformers Secondary. •Run-DC maintains the ICs stable operation...
  • Page 66 •As the Transformer discharges, the Secondary Windings develop secondary voltages •The DC Voltage supplying the Switching IC becomes insufficient. •As the Capacitor discharges the Switching IC requires additional voltage to maintain stable operation. •Additional Run-DC is provided to the Switching IC from the Transformers Secondary.
  • Page 67 TELEVISION SWITCH CIRCUIT REVIEW STANDBY OPERATION On-tim e PHC DC AC In O n-tim e 1STB13 •Micon powered by Standby Voltage from Transformer secondary •Micon turns on the Photo 1STB13 Coupler ST R- F6514/5 Ocp/ •Photo Coupler adds DC shortening IC On time •TV is now in Standby Mode •Regulated DC added to RunDC...
  • Page 68 • TV Micon is powered by the Transformers Secondary Voltages. • The Micon Turns on the Photo Coupler. • The Photo Coupler adds additional DC to the Switching IC’s feedback reducing its On Time. • The TV is now in Standby Mode. •...
  • Page 69 TELEVISION SWITCH CIRCUIT REVIEW POWER ON Relay • Power ON command received by Micon AC In • Micon turns off Photo Coupler and turns on Main Power Relay and circuits • Error Amp monitors B1 1STB13 and controls Switching IC off time.
  • Page 70 • When power is turned on the CPU turns off the Photo Coupler and turns on the relay for the main Power Circuits (B1 Voltage). • Turning off the Photo Coupler means there is no control over the output • The Error Amp is activated and Monitors the B1 supply. •...
  • Page 71 TELEVISION POWER FACTOR CIRCUIT •Used in Some HDILA models. •Power demand of TV circuits cause AC line current spikes. •AC spikes affect rectified AC Line Without Power Factor Circuit...
  • Page 72 • Some HDILA TV Power Supplies utilized a Power Factor Circuit (PFC). • The High current demand of the Ballast PWB and Circuit exceeded the ability of the Standard Bridge Rectifier/Capacitor combination to deliver the power. • As the AC would rise, the Capacitors ability to supply power diminished causing the Ballast Circuit to Pull Power from the AC supply.
  • Page 73 TELEVISION POWER FACTOR OPERATION Transformer Secondary Current •PFC controls FET ON/OFF Operation •Eliminates AC Line Spikes •Smooth Power Output...
  • Page 74 TELEVISION •The PFC IC controls the Power FET. •The FET increases Power output during spikes. •The PFC IC monitors the incoming DC to the Transformer and Outgoing DC from the Transformer. •As the Transformer Charges, the PFC IC turns the FET ON. •When the Transformer is fully Charged and begins to discharge into it’s secondary, the PFC IC turns the FET OFF.
  • Page 75 TELEVISION POWER FACTOR IC MC33262D-X...
  • Page 76 Pin Explanation 1. Monitors B1 Line and provide Voltage Feedback to IC 2. Compensation to allow IC to compensate for Temperature changes during operation 3. Samples Bridge Rectifier Output. Turns FET OFF when Bridge Rectifier goes to 0.0VDC. 4. Monitors FET current. 5.
  • Page 77 TELEVISION FUNCTION CHECK PROCEDURE The following will explain steps that will allow the Powering Up of the Power Supply in a Stand Alone condition using (2) AA Batteries. This means that no other PWBs should be connected to the unit during the test. Stand Alone power on of the units allows a technician to test the Power Supply without the effects of other PWBs, possibly isolating the trouble.
  • Page 78 TELEVISION FUNCTION CHECK PROCEDURE INSPECT UNIT UNINSERTED CONNECTOR PARTIALLY INSERTED CONNECTOR DAMAGED CHASSIS...
  • Page 79 •Before and After performing any troubleshooting it is necessary to visually inspect the TV to ensure all connectors are properly inserted and there are no additional damaged or broken parts. •These items may act as clues to help determine the cause of TV symptoms.
  • Page 80 TELEVISION FUNCTION CHECK PROCEDURE REQUIREMENTS FOR POWER ON AC line Voltage Standby Voltage Circuit function Power On Signal from Micon 4. In some models, Main AC line voltage switch must be closed...
  • Page 81 Provided all circuits function within a Power Supply, there are only (3 or 4) requirements for the Power Supply to function AC Line input voltage: This voltage will be rectified and provide the DC for the Switching Circuits. Standby Voltage: This voltage is needed to power the Micon. Power On signal from Micon: The micon receives the Power on signal from the Remote or Front Panel.
  • Page 82 TELEVISION FUNCTION CHECK PROCEDURE PROCEDURE STEPS OF PROCEDURE • Remove PWB from TV HD-52G786 • Inspect PWB SRP-9022A-M2 PWB • Ensure Main Power Switch is Closed Reference YA293 Schematic • Plug unit into AC line • Test Standby Circuits • Simulate Micon “Power On”...
  • Page 83 Pictured are the (2) example PWBs that will be used in this procedure This is a quick and simple procedure that can be used to quickly test the circuits operation. Ensure you have properly inspected the PWB for Shorted, Open, Damaged or Missing components. The Steps of the Procedure are as follow: Remove PWB from Television Inspect PWB for Shorted, Open, Damaged or Missing components.
  • Page 84 TELEVISION FUNCTION CHECK PROCEDURE INSPECT PWB BROKEN COMPONENT NOT FULLY INSERTED MISSING SHORTED...
  • Page 85 •Before performing any troubleshooting steps it is necessary to visually inspect PWBs. •Failure to Inspect PWB for these Items could result in further damaging the PWB •Catching these items prior to troubleshooting can prevent wasted troubleshooting efforts.
  • Page 86 FUNCTION CHECK TELEVISION PROCEDURE PROVIDE AC AND CHECK STANDBY VCC HD-52G786 AV-48P776/H SRP-9022A-M2 PWB SSR-9001A-M2 PWB Reference YA293 Schematic Reference YA318 Schematic Short CN90SE Plug in AC cord Plug in AC cord Check for Standby VCC at IC922 Check for Standby VCC at IC9141 IC922 Short CN90SE...
  • Page 87 When the AC cord is plugged in, the Standby Circuits should function. This Circuit will supply the VCC to the Micon. Check this Voltage prior to continuing. SRP-9022A-M2 PWB The SRP-9022A-M2 PWB utilizes Power Supplies whose Standby VCC is created by a circuit that is separate from the Switching Circuits.
  • Page 88 TELEVISION FUNCTION CHECK PROCEDURE CHECK STANDBY CIRCUITS AV-48P776/H SSR-9001A-M2 PWB Reference YA318 Schematic CHECK CIRCUITS 1. F905 Surge Protection 2. D901 and C907 Main rectifier 3. IC911 Switching Regulator Startup D911, R911 and C914 5. T921 Switching Transformer Current Feedback R923, C903 and R920 7.
  • Page 89 • The SSR-9001A-M2 PWBs Switching Circuits Operate in Standby Mode, therefore it is possible to partially test these circuits function. • An Operational Standby Voltage Source is a good sign that the other circuits are functional. • It is still necessary to fully power up the Supply to ensure it is fully functional as some components may fail under a higher load voltage.
  • Page 90 TELEVISION FUNCTION CHECK PROCEDURE PROVIDE “POWER ON” HD-52G786 AV-48P776/H SRP-9022A-M2 PWB SSR-9001A-M2 PWB Reference YA293 Schematic Reference YA318 Schematic AV-48P776/H 1. Apply 3VDC to CN90G 1. Apply 3VDC Pulse to pin3 “MAIN_POW”, use pin2 CN9003 pin12 “B1_POW” “GND2”as Ground and CN001 pin12 “RELAY”, use CN003 pin15 as Ground 2.
  • Page 91 • Using (2) AA batteries connected in SERIES, connect the Positive end to the connector specified each PWB. • Connect the GROUND end to the ground location specified. • The AA batteries will provide a 3VDC to the Main Power Relay and other circuits necessary to turn on the Power Supply.
  • Page 92 TELEVISION FUNCTION CHECK PROCEDURE ORDER OF FUNCTION CHECK 1. Surge Protection 2. Main rectifier 3. Switching Transformer 4. Switching IC 5. Startup 6. Photo Coupler 7. Run DC 8. Error Amp 9. Secondary Voltages 10. Current Feedback 11. Main Relay 12.
  • Page 93 •By applying 3VDC to turn on the supply, you are now able to troubleshoot the supply in a Stand Alone Fully Powered Condition. This eliminates shorts caused by other PWBs. •Check the circuits listed in the order specified to find PWB trouble. •If a Circuit is found to be unsatisfactorily functional, use the troubleshooting procedures in the sections that will follow to aid in testing the specific circuit.
  • Page 94 TELEVISION FUNCTION CHECK PROCEDURE BATTERY TESTING DEVICE...
  • Page 95 •(2)AA batteries may be used to supply a Power ON DC to the Power Supply •Use the images to create a simple test Jig. •Ensure that you properly connect the batteries in series with the positive of one battery connect to the negative of the other •When connecting wires to the batteries it is wise to use (2) different colors to represent positive and negative to prevent later confusion.
  • Page 96 TELEVISION TROUBLESHOOTING The following goes over procedures that will allow the testing of specific circuits of the Power Supply. These steps must be carefully followed to prevent damage to PWB or injury to self.
  • Page 97 TELEVISION TROUBLESHOOTING SWITCHING IC STR-G9626 STR-X6737 STR-F6167 •Check VCC •Check Ramp Voltage at Feedback Pin •Check for DC voltage at FET input •Check that FET is not shorted to GND •Always Replace IC and Capacitor together.
  • Page 98 •The (3) versions of the Switching IC are shown; G, F and X. These pin out schematics of the ICs can be used to assist with troubleshooting. •Check the ICs VCC for approximately 14V. This is the StartUp and RunDC voltage that is required to power the amp. •Check for the Ramping Voltage at the Feedback Pin.
  • Page 99 TELEVISION TROUBLESHOOTING CHECKING SWITCHING IC SUPPLY “STARTUP” •Power On and check IC supply •Usually a Diode/Resistor and Capacitor connected directly to the AC and bypassing the Main Bridge Rectifier •Desoldered components to isolate StartUp supply if needed •Always Replace Capacitor and IC together.
  • Page 100 • Use the FUNCTION CHECK PROCEDURE to power on the Television. • Check the Switching ICs pin4 VCC for approximately 14VDC. This is supplied by the StartUp circuit previously outlined. • If this voltage is not present, check the circuits that supply this voltage to the IC. •...
  • Page 101 TELEVISION TROUBLESHOOTING CHECK BRIDGE RECTIFIER YA389 Schematic YA293 Schematic Rectifier Circuits always used to Provide DC Out from AC In Check Incoming AC Check DC Voltage at Capacitor Desolder components after capacitor to isolate Bridge from shorting...
  • Page 102 TELEVISION • The Bridge Rectifies converts the AC line input into a DC voltage that is usable by the TV circuits. • Begin troubleshooting this Device by first checking the incoming AC line voltage, then checking the DC voltage at the Capacitor. •...
  • Page 103 TELEVISION TROUBLESHOOTING RELAY FUNCTION CHECK Use this circuit to test the Relay Follow Steps to assist...
  • Page 104 TELEVISION Connect power supply as shown in figure. Use a 1K ohm 10 watt resistor as a current limiter. Set voltage to 3V and check current reading. Less than .3 Troubleshoot Components amps • It is possible that the Relay contacts may wear or the supply circuits to the relay may not function.
  • Page 105 TELEVISION TROUBLESHOOTING REGULATOR CHECK Use this circuit to test the Regulators Follow Steps to assist...
  • Page 106 TELEVISION Connect power supply as shown in Figure. Positive lead should be connected to Regulator IC Pin1 and negative lead should be connected to ground. Set Power Supply to 2V and observe current readings on the Power Supplies current meter. Troubleshoot and Less than 0.75 Amp repair any shorted...
  • Page 107 TELEVISION TROUBLESHOOTING FEEDBACK PHOTO COUPLER Isolated Live Connect the DC supply so that it will replace the voltage that normally would supply the voltage Reference YA293 Schematic Photo Coupler...
  • Page 108 TELEVISION • Check the Operation of Feedback Photo Coupler by connecting the circuit shown. • When the Photo Coupler becomes operational you will see the voltage at the emitter of the Photo Coupler Transistor rise from 0 to approximately 5V. •...
  • Page 109 TELEVISION TROUBLESHOOTING SYMPTOM/CAUSE B1 VOLTAGE HIGH/ LOW SECONDARY VOLTAGES POWER ON/OFF RAPIDLY • Leaky Error Amps may can cause High B1 voltages • This can result from many things, but the likely culprit is the supply to the switching IC. •...
  • Page 110 If you need more information on Computer and Electronic Repair, please visit these websites to improve yourself. http://www.fastrepairguide.com http://www.protech2u.com http://www.plasma-television-repair.com http://www.lcd-television-repair.com Happy Repairing!! Highly Recommended Repair Ebook: If you’re a LCD Monitor repairer, then this is the best guide for you. Why? Because, the author revealed all his LCD Monitor Repairing secrets for you.

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