JVC Television Power Supply Training
Contents
1. the voltage SSE would supply the voltage Photo Coupler TELEVISION a e hare crt adn ob Fone Sine I enarsang nie resin POEs na anum wowi ase e toni saxi ga amio E Check the Operation of Feedback Photo Coupler by connecting the circuit shown When the Photo Coupler becomes operational you will sce the voltage at the emitter af the Photo Coupler Transistor rise from 0 to approximately 5V When checking this circuit using the FUNCTION CHECK PROCEDURE you will notice 1V difference between the Photo Coupler Transistors pins ig cin Whe resi aut bere mir ma gound JVC TELEVISION TROUBLESHOOTING JVC SYMPTOM CAUSE BI VOLTAGE HIGH LOW VOLTAGES Leaky Error Amps may can cause High B1 voltages Check voltages at error amp Fit is excessive then change The Zener Diode on between the Photo Coupler and Error Amp may cause similar Low Power issues POWER ON OFF RAPIDLY This can result ftom many things but the likely culprit is the supply to he switching This is similar to what causes lamp flicker the power supply is oscillating due to insufficient supply voltage Check the circuit that supply the Run DC and NO STANDBY VCC In many HDILA models the Transfo2. Minimum pins 5 pins This is one of the various types of Switching Devices used in JVC Power Supplies In the previous explanations we called it SW1 On the Schematics previously outlined it is the Regulator 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 TELEVISION JVE SWITCHING DEVICE Properties 07V Applied to Pin 1 will turn OFF the FET FET will turn on after pre determined time Applying a 2 0V pulse to Pin 1 reffeshes the IC prior to pre determined time When 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 short between pin2 and pin3 ofthe 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 If we wants to turn ON the IC prior to the internally decided time we can apply 2VDC to pinl This means we can turn ON the FET and turn OFF the FET at any time we want JVC TELEVISION SWITCHING DEVICE Internal Startup When we apply approximately 12V to the IC s internal circuit functions
3. 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 The charge discharge of these circuits happens quickly causing AC line Current spikes during these Peak Power Demand periods As shown in the figure this causes AC voltage dips and affects the Rectified 1 Voltage TELEVISION JVC POWER FACTOR OPERATION controls FET ON OFF Operation Eliminates AC Line Spikes Smooth Power Output TELEVISION JVE PFC IC controls the Power FET The FET increases Power output during spikes PFC IC monitors the incoming DC to the Transformer and Outgoing DC from the Transformer the Transformer Charges the 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 TELEVISION POWER FACTOR IC Jvc MC33262D X Pin Explanati 2 Monitors Line and provide Voltage Feedback to IC Compensation to allow IC to compensate for Temperature changes during operation Samples Bridge Rectifier Output Tu
4. TELEVISION JVC 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 Some failures and their symptoms TELEVISION JVC 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 Jvc TELEVISION MODEL IDENTIFICATION 6030932 0014 z MODEL NO AV 32MF36 120V 60Hz SCREEN SIZE DIAGONAL 32 inches US LISTED econ NO 3 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 For example YA319 is the service manual but YA319B would be a revision The Example shows that the AV 32MF36 has 4 versions The example shows Z Version of this model The Model Number listed at the top of the model label will always be the same for all versions The TV Model Version is usually shown to the right of
5. Photo Coupler The Photo Coupler must be turned On in Standby Mode and turned Off in Normal Mode In the Standby Mode additional DC is provided from the ICs Supply Voltage using the Photo Coupler CPU s outputs a High turning the Photo Coupler on The Photo Coupler supplies additional FeedBack DC to pinl As we already saw in the chart this must be added in standby and must be removed in normal mode TELEVISION SWITCHING OPERATION Jvc SUPPLEMENT POWER RUN DC During Standby Mode the Run DC may be insufficient to keep Switching IC ON 1 Power is supplemented by Regulated Voltage 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 For this reason a regulated DC voltage from a higher tap is used to supplement the RUN DC This voltage must be regulated otherwise in normal operation the voltage will be too high and will destroy the IC This circuit is not used in all models TELEVISION SWITCHING OPERATION Jvc PHOTO COUPLER DURING POWER ON At Power On Micon outputs LOW Photo coupler is inactive On Time is normal relay is turned On eu At Power on Micon
6. Power Supply to function 1 AC Line input voltage This voltage will be rectified and provide the DC for the Switching Circuits 2 Standby Voltage This voltage is needed to power the Micon 3 Power On signal from Micon The micon receives the Power on signal from the Remote Front Panel It will then send the Power On Signal to the Power Supply circuits This always turns on a relay that activates the Main Power Circuits 4 Main AC line voltage switch must be closed In some units primarily HDILA models there is a switch that controls the AC line voltage In HDILA models this switch is the Temperature Sensor that is mounted above the lamp In other models this may be a Main Power switch on the back of the unit This switch must be closed before the Television may be powered on TELEVISION CHECK PROCEDURMWG PROCEDURE STEPS OF PROCEDURE Remove PWB from TV Inspect PWB Ensure Main Power Switch is Closed Plug unit into AC line Test Standby Circuits Simulate Micon Power signal Check Switching Circuits AVAIT Reference Schematic Pictured are the 2 example PWBs that will be used in this procedure This is a quick and simple procedure that 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 1
7. and turns ON the FET Drive When the internal circuit is turned on the driver circuit tums 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 Oscillator The IC has an Oscillator for timing control This oscillator decides its natural on off time This means after applying the startup DC after a pre determined time it will come on OCP FB This is the control input to override the oscillator s timing By applying 0 7V to this input we can turn OFF the internal circuit and FET By applying a 2 0V pulse we can turn it back ON TSD Thermal Shut Down This is for the thermal protection When the IC overheats this circuit tums off the IC and latches it We have to unplug the power to restart OVP The OVP circuit monitors the startup DC If the voltage exceeds the specified level it turns off the IC and latches it We need to unplug the power to restart Latch This is the latch circuit that latches and holds the shut down circuit outputs TELEVISION JVC SWITCHING DEVICE Turn ON acin Apply power to the IC When the tank Capacitor charges up to the Start up voltage IC starts conduction R930 i Now it can switch the RAW DC through the Transistor if it is connected The Switching FET turns ON Referens Schematic 52004 Main PWB for This start up circui
8. and check all voltages supplying the Standby VCC circuit SSR 9001A M2 PWB The Standby VCC for the SSR 9001A M2 PWB is created by the Switching Circuits Lf the Standby VCC circuit is not functional troubleshoot the Power line from the Transformer supplying this voltage In this case it is the 28V line Remember In Standby Mode the Power Supply voltage is reduced The 28V line will put out 14V in Standby Mode CP942 and CP941 may be removed to eliminate the possibility of others circuits creating shorts to this supply Check the DC at C938 TELEVISION E 6 AVASPTIUM SSR 9001A M2 PWB Reference 18 Schematic CHECK CIRCUITS 73 Surge Protection and Main rectifier icon Switching Regulator Switching Transformer 3623 and R20 7 FR915 and D912 om FUNCTION CHECK PROCEDURE JVC CHECK STANDBY CIRCUITS Current Feedback Run DC Photo Coupler 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 SRP 9022A M2 PWB does not utilize a Switching Circuit during Standby Mode Therefore these circuits cannot be tested
9. in this PWB TELEVISION CHECK PROCEDURE JVC PROVIDE POWER ON Reference Scheme 1 Apply SVDC Pulse to pin2 ht POW GL CNODI pi RELAY pal as Ground Check ali Supply Vols 3 Check Switching Circuits HD S2GTMG SRP 9022A M2 PWB Reference YA293 Schematic 1 Apply SVDC w MAIN PON use pin TOND as Ground 2 Check all Supply Voluges Check Switching Cice Fanion LAMPIREC FAN LOCK 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 batteries will provide 3VDC to the Main Power Relay and other circuits necessary to turn on the Power Supply Test all output voltages of the Supply If the supply does not activate ensure the source is connected properly then troubleshoot the Switching Circuits Any external Power Supply may be used to provide the 3VDC turn on voltage TELEVISION 2 Main rectifier 6 Photo Coupler 2 Emor Anp 9 Secondary Voliages 10 Feedback 11 Main Rely 12 Main Relay Drive Switching FUNCTION CHECK PROCEDURE ORDER OF FUNCTION CHECK JVC applying 3VDC to turn on the supply you are now able to
10. 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 TELEVISION SWITCHING OPERATION JVC ERROR Emoramp monitors i Bl Controls Photo Coupler to Reduce on time if B1 exceeds spec When the on time is normal sufficient energy is transferred and the B1 supply High voltage etc is active If the Supply is more than required it must be reduced By controlling the ON OFF timing of the supply the Supply voltage can be controlled This is done with the use of an Error Amp Error Amp monitors the 1 Supply and Activates the Photo Coupler feedback as needed to reduce the ON time of the Switching Supply TELEVISION JVE SWITCHING OPERATION REFRESH In practical use we need to restart the IC earlier than the pre determined time Apply 2 0V pulse to During the negative edge the IC will refresh reset and turns on again 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 case of additional power requirements by the TV circuits inste
11. taken from the 52004 Schematic of the Main PWB 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 When troubleshooting it is NECESSARY to use the respective ground Live of Isolated of the device you are measuring Additional components located along the dotted line ensure circuit isolation while passing all Power or Control signals These components are the Relay Switching Transformer Photocoupler and the Capacitors that are used to connect the Live and Isolated grounds TELEVISION T 3 con and as POWER SUPPLY COMPONENTS Sage Protection TOSI DOSE and COSI Standby Power Lie Fiter Main eter Switching Regulator p Switching Transformer Curent Feedback Run De Maio Relay Main Relay Drive 9 Schematic 52004 Main PWB JVC Reference Schematic 52004 Main PWB for Schematic Details 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 Pow Supplies may omit or add circuits the general function of all JVC Power Supplies are the F901 and VASOL Surge Protection Stops circuit functio
12. the Serial Number on the Model Label TELEVISION SERVICE MANUAL SUPPLEMENTS JVC ren eT e JVC TUUS asse CL i AVAteTIS Service Supplement Supplements show Corrections Additions and Differences that may have occurred during the production of a TV Model No VASISB Picus he of AVP 770 waa change 2006 6 Therefore thi sevice manual describes only the Heens which difer rom those ofthe A V 48P7767H service manual For details other tan those seri in this manual please refer to he AV ASP7T6H service manul 20511 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 The Original Manual will only show the original Service Information for a model but Service Manual Supplements may list information that is important to the service of a model Ensure that you use the Model and Model Version when looking for documents on to ensure you are getting the correct information TELEVISION SWITCHING POWER SUPPLY Jvc oe ofthe Taken froen Schematic 52004 Main PWB This is the Power Section from the AV 32F703
13. troubleshoot the supply 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 specifie circuit The SSR 9001A M2 PWBs Switching Circuits Operate in Standby Mode therefore it is possible test many of these circuits by only applying AC line voltage Although Standby Mode will not provide full Output Voltage from the Transformer Secondary Bl Power On at the correct Voltage is a good sign that the PWB has defects Refer to SWITCH CIRCUIT REVIEW section for assistance identifying the circuits and their functions TELEVISION row CHECK PROCEDUR VG BATTERY TESTING DEVICE 2 AA batteries may be used to supply a Power ON DC to the Power Supply 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 Always measure the voltage to ensure you have a proper connection between the batteries and they are outputting the correct voltage TELEVISION JVC TROUBLESHOOTING The following goes over procedures t
14. PERATION POWER SUPPLY TYPES F F i JVC There are 2 general types of circuit configurations used in JVC Power Supplies gt HH AC tine TYPE 2 POWER ON Switching Circuits ONLY supply Power after TV Power Standby Voltage for Micon is supplica from DC Voltage tapped directly incoming There are 2 general typ s of circuit configurations used in JVC Power Supplies TYPE 1 ALWAYS ON Utilizes a Standby Mode when TV Power is OFF tandby Voltage for Micon is supplied by Switching Circuits Example shown that T2921 supplies voltage to the DC Regulator 172922 Micon will tum ON RY2 2 to allow Voltage flow when the TV is turned ON Reference Schematic YA321 Power and Def PWB for Schematic Details 2 POWER ON Switching circuits supply Power after TV Power is ON Standby Voltage for Micon is supplied from DC Voltage tapped directly from incoming AC line the example shown the Standby VCC is supplied by T951 0954 0957 and C951 Micon tums ON RY95I this allows AC Voltage to flow to the Switching Circuits when the is tumed ON Reference Schematic 52004 Main PWB for Schematic Details TELEVISION SWITCHING OPERATION JVC STANDYBY MODE In Standby Mode very few devices are functional They need only very lit
15. Remove PWB fiom Television Inspect PWB for Shorted Open Damaged or Missing components Ensure Main Power Switch is Closed Shorted to allow AC in circuit Plug unit into AC line to provide voltage to Standby circuits Test Standby Circuits and Check Standby Operation of Switching Circuits Simulate or Activate Micon Power On signal to activate Main Power Circuits Check Power On function of Switching Circuits 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 TELEVISION FUNC HON CHECK JVC PROCEDURE PROVIDE AC AND CHECK STANDB WD SIGTM SRP 9022 M2 PWB Reference V A293 Schematic SSR 9001A M2 PWB Reference VASIB Schematic ae Plug in AC cord Cesk for Standby Check for Standby VOC at 10922 1 Plugin AC cord S 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 Check for the Standby VCC at the specified location Lf the Standby VCC is not functional begin at the incoming AC Line Voltage
16. a resistor if the switch is turned on the current will rise slowly through the inductor and the resistor The current ramps up and Reaches maximum and stays constant When the current does not change any more the inductor is fully charged Capacitors and inductors behave similarly but opposite Capacitors can hold the charge but inductors can not It has to be discharged If there is no path to discharge it will make eddy current through the coil and produce heat The basic of Switching power supply is the effective and controlled use of using the discharged energy TELEVISION p ASIC SWITCHING JVC INDUCTOR DISCHARGING Once the Inductor is finished charging turn SWI 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 When the current flow to the Fully Charged Inductor is interrupted by closing SW the stored energy is released as Heat This stored energy is utilized in the Switching Power Supply TELEVISION ASIC SWITCHING JVC TRANSFORMER OPERATION DC Voltage If there is a secondary winding during the off time energy will be transferred into the secondary Off swt In other words Transformer charges during ON time Discharges during OFF time Rs If the coil has a secondary winding an
17. ad of waiting for the internal Timing generator to turn on the IC we can refresh the IC raising above 2 0V and dropping it back to zero on the negative edge the IC resets again and starts conduction This is known as the Refresh Circuit TELEVISION 1 FI and VADOT CK Cot and C903 D001 and COUT 9 ROIS and D912 11 pas 12 SWITCH CIRCUIT REVIEW POWER SUPPLY COMPONENTS I3 Surge Pre 2 T951 DOS and CUSE Stay Power Lie Fe Main ei Switching Stamp Switching Transformer Feedback un DC Ree Main Relay Mois Relay Deve Emoe Ang JVC Schematic 52004 Main PWB Reference Schematic 52004 Main PWB for Schematic Details For Review look over the Schematic and identify these components and their functions 1 F901 and VA901 Surge Protection Stops circuit function if High Current shori is detected 2 1951 D95457 and COSI Power Supplies Standby DC voltage to Micon 3 CODI C902 and C903 Line Filter Filtering of AC line noise 2 D901 and C907 Main rectifier Provides rectified DC to Switching Regulator and Switching Transformer Switching Regulator Regulates Switching Voltages of Transformer 6 D911 ROIL R930 and C914 Provides Startup DC for Switching Regulator until Transformer conduction begins 19 Switching Transfor
18. arges into the 7 Secondary when FET shuts off DC Voltage supplying the Switching IC becomes insufficient Run DC provided to IC from the Transformers Secondary Run DC maintains the ICs stable operation the Transformer discharges the Secondary Windings develop secondary voltages DC Voltage supplying the Switching IC becomes insufficient 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 This Voltage maintains the ICs continuous operation and the Circuit becomes stable TELEVISION switcHcircuirreview VE STANDBY OPERATION i a Micon powered by Standby Voltage from Transformer secondary Micon turns on the Photo Coupler Photo Coupler adds DC shortening IC On time ew TV is now in Standby Mode Regulated DC added to RunDC 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 Since the on time is reduced all voltages from Transformer are reduced including the Run DC that helps power the Switching IC Regulated DC is added from a higher Transformer winding to e
19. ctifier Desoldered components to isolate StartUp supply if needed Use the FUNCTION CHECK PROCEDURE to power on the Television Check the Switching ICs 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 Check the Diode Resistor and Capacitor that make up this circuit for opens or shorts This circuit is connected to the Photo Coupler circuit so it may be necessary to check or desolder these components to eliminate the possibility of them being the trouble Desoldering and Lifting the ICs pin 4 will allow the check of this voltage without the influence of the Switching IC Always Replace the IC and the Capacitor on the VCC input together TELEVISIONTROUBLESHOOTING VE CHECK BRIDGE RECTIFIER Y A389 Schematic Y A293 Schematic Rectifier Circuits always used to Provide DC from AC In Check Incoming AC Check DC Voltage at Capacitor Devolder components after capacitor ta isolate Bridge from shorting TELEVISION JVC 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 line voltage then checking the DC voltage at the Capacitor It may be necessary to desolder components to elimi
20. d 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 1 When the Switch is turned on the primary charges When the Switch is turned off the charged core of the inductor discharges into the secondary 3 Since we are interested in DC output the addition of the Diode and Capacitor at the secondary will allow for the energy to be stored in the Capacitor This stored energy is our Secondary DC voltage 4 the switch is turned off prior to fully charging the inductor the transferred energy will be less This shows that by controlling the Switch s on off time we can obtain necessary secondary voltage Transformer Switch or any Switching Device and a Control Circuit to control on off switching make up a Switching Supply JVC TELEVISION p ASIC SWITCHING SUMMARY 1 Apply an unregulated DC Voltage to the Transformer s Primary 2 Switching the Primary ON and OFF will result in Secondary Voltage 3 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 TELEVISION JVC SWITCHING DEVICE STR Fxxxx IC Very reliable construction Allin one package Protection circuits
21. e 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 TELEVISION SWITCH CIRCUIT REVIEW Jvc RAMPING VOLTAGE De Voltage ber I Start up Voltage applied to IC turns On FET allowing current through Inductor Current Flow allows the Inductor to charge and Ramp Voltage to Build at IC 4w The Start up DC is applied to the ICs 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 At the same time the Inductor is charging a Ramp Voltage builds up at the Feedback of the Switching IC TELEVISION JVE SWITCH CIRCUIT REVIEW RAMP VOLTAGE FEEDBACK The ramp voltage is applied to 1 When the ramp voltage reaches 0 7V the FET will shut off 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 7 removing the 0 7 V will allow the IC to resume conduction in pre determined time TELEVISION JVE SWITCH CIRCUIT REVIEW RUN DC Transformer disch
22. ernal timing circuit the FET will start again after a pre determined time TELEVISION JVE SWITCHING DEVICE Turn Off 22 When the FET conducts a ramp voltage is generated at pin 2 We use this ramp to turn FET off and hence create a switching action Taping Votiage bas bere sed fed back op Tris feedback Resistor Capacitor opens up the IC will never be tured off The transformer and the IC will overheat and shutdown occurs Reference Schematic 52004 Main PWB for Schematic Details We already discussed that the IC is designed such that if we apply 0 7V at pinl 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 We use this ramping voltage at pin to turn off the IC When the inductor primary charges Current increase through the source resistors It causes a ramp voltage at pin2 and is applied to pin If this feedback Resistor Capacitor opens up the IC will never be turned off The transformer and the IC will overheat and shutdown occurs ELEVISION T SWITCHING DEVICE Jvc SECONDARY VOLTAGES hw 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 When DC is applied pin3 current will flow through the t
23. hat 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 TELEVISION TROUBLESHOOTING JVC SWITCHING IC oe Check VEC 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 3 versions of the Switching IC are shown F and X These pin schematics of the ICs can be used to assist with troubleshooting Check the ICs 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 This voltage will vary between models but 7 VDC is the average measurement Some PWBs have shown 1 4VDC at this pin Check for DC voltage at FET input It should be the same as the Input to the Transformer and is usually about 170VDC Check that the FET is not shorted to GND Ensure the Power Supply is Off before making this measurement Always Replace the IC and the Capacitor on the VCC input together TELEVISION troypiesHootinc CHECKING SWITCHING IC SUPPLY STARTUP Power On and check IC supply Usually a Diode Resistor and Capacitor connected directly to the and bypassing the Main Bridge Re
24. mer Provides voltages to all circuits 8 ROD ROIS and R914 Current Feedback Provides current feedback to Switching IC to stop conduction 9 ROIS and D912 Run DC Provides additional DC to Switching IC 10 D917 and D914 Refresh Provide Refresh voltage to Restart IC Regulation 11 D945 RYOSI Main Relay Allows Power flow to SW IC and SW Reg Also functions as relay for Degauss 12 Main Relay Drive Controls function of Main Relay 13 10921 Error Amp Monitors Line Voltage This is the basic circuit configuration and use for all JVC Power Supplies While some Power Supplies may omit or idd circuits the general function ofall JVC Power Supplies are the same TELEVISION JVE SWITCH CIRCUIT REVIEW We will quickly go through the operation of a Switching Supply EVISION BIO SWITCH CIRCUIT REVIEW Jvc BRIDGE RECTIFIER E The AC line Voltage is converted to DC by the Bridge and Capacitor 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 SWITCH CIRCUIT REVIEW JVE APPLIED DC 3l dA Raw DC flows through the transformer to the Switching Device When the FET is turned On it will allow current flow to ground voltage flows through the Transformer to the to FET When th
25. n if High Current short is detected T951 0954 57 and C951 C901 C902 and C903 D901 and C907 acon DOLI R911 R930 and C914 R912 R913 and R914 R915 and D912 D917 and D914 D945 RY9SI Ico Standby Power Supplies Standby DC voltage to Micon Line Filter Filtering of AC line noise Main rectifier Provides rectified DC to Switching Regulator and Switching Transformer Switching Regulator Regulates Switching Voltages of Transformer Startup Provides Startup DC for Switching Regulator until Transformer condoction begins Switching Transformer Provides voltages to all circuits Current Feedback Provides curent feedback to Switching IC to stop conduction Provides additional DC to Switching IC Provide Refresh voltage to Restart IC Regulation Main Relay Allows Power flow to Switching IC and SW Reg Also functions as relay for Degauss Main Relay Drive Controls function of Main Relay Error Amp Monitors Line Voltage TELEVISION p ASIC SWITCHING JVC INDUCTOR CHARGING De vonage 1 Switch SWI off 2 Apply a DC to the inductor as shown Wa 3 Tur SWI on and the Current m rises slowly 4 The Inductor charges to its maximum i 5 After charging is complete the current stays constant 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
26. nate them as a possible cause of problems If so desolder the components after the Capacitor TELEVISION JVC TROUBLESHOOTING RELAY FUNCTION CHECK 2 1 Use this circuit to test the Relay 4 Follow Steps to assist current limiting resistor It is possible that the Relay contacts may wear or the supply circuits to the relay may not function Use this circuit to test the relays function Follow the Steps to assist in troubleshooting JVC TELEVISION TROUBLESHOOTING ME REGULATOR CHECK Use this circuit to test the Regulators Follow Steps to assist TELEVISION JVC E Regulators used in the Power Supp The voltages shown apply to SV regulator fa larger regulator is being tested follow these mis 1 Positive On input Negative to GND lt lt 2 Begin by inputting 24V Check current fit is excessive then there 201 4 Raise voltage approx 4 volis above 1 regulator voltage and check that the DC dacs x not exceed the ICs rating 5 Always monitor curent and stop if current M becomes excenive i TELEVISION TROUBLESHOOTING VG FEEDBACK PHOTO COUPLER Connect the DC supply o at
27. nsure the IC does not shut when the TV is in Standby Mode TELEVISION JVC SWITCH CIRCUIT REVIEW POWER ON Power ON command received by Micon Micon tums off Photo Coupler and turns on Main Power Relay and circuits Error Amp monitors and controls Switching IC off time Refresh Circuit added in case TV circuits require additional power Refresh circuit allows Switching IC to be tumed On whenever needed b applying 2V pulse to I When power is turned on the CPU turns off the Photo Coupler and turns on the relay for the main Power Circuits Voltage Turning off the Photo Coupler means there is no control over the output The Error Amp is activated and Monitors the B1 supply The Error Amp uses the Photo Coupler to control the Switching IC s Off times In case of additional power requirements by the TV cireuits instead of waiting for the internal Timing generator to turn ON the Switching IC we can refresh the IC The Refresh circuit is added and works by raising above 2 0V and dropping it back to zero On the negative edge the IC will reset again and start conduction TELEVISION JVC POWER FACTOR CIRCUIT Used in Some HDILA models Power demand of TV circuits cause AC line current spikes spikes affect rectified AC Line Without Power Factor Circuit
28. ransformer and charges it The content will generate 7 V on pind This is applied to pin to turn it off When the Inductor shuts off the Inductor discharges the energy to the secondary Repeating the ON and OFF process causes a switching action This action causes the transformer to charge and discharge generating generates Secondary Voltages The IC s startup voltage is through a high value resistor When the IC functions it drains current through pind and the supply is insufficient and cannot continue to supply voltage to the The IC could Shut OFF due to insufficient Supply Voltage We want the IC to be permanently on and turn ON OFF the FET But if the IC goes off the control is not possible Total reset occurs causing a pulsating supply TELEVISION SWITCHING DEVICE SUPPLEMENT POWER RUN DC JVC Supplement the start up DC with Run DC IC Power Supply becomes stable Transformer fully Charges Discharges Reference Schematic 2004 Main PWB for Schematic Details 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 TELEVISION TYPE 1 ALWAYS ON Standby Voltage for Micon is supplied by Switching Circuits Standby Mode used when TV SWITCHING O
29. rmer Regulator or Rectifier circuit fails Startup DC Measure the Ramping Voltage at the Feedback Ws less than this means the IC is not stable Check the input to the Bridge Rectifier then measure the DC output voltage at all points up to the Regulator to find the faulty component In Models with Standby suppli by Switching Circuits measure the supply voltage to this circuit Many times other PWBs have failed in the TV shorting the supply line for the Standby Voltage Ensure the Circuit Protectors have not blown on this supply line LAMP FLICKER IN HDILA Run DC is important to maintaining a stable supply if this is low the supply may oscillate This oscillation will appear in the voltage and in HDILAS this may cause the lamp to flicker Check the circuit that supply the Run DC and Startup be Measure the Ramping Voltage at the Feedback fit is ess than 7V this means the IC is not stable
30. rns FET OFF when Bridge Rectifier goes to 0 0VDC Monitors FET current Switches FET ON when Transformers Secondary Current Reaches 0 0VDC IC Ground Controls FET operation IC VCC TELEVISION JVE 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 These steps must be carefully followed to prevent damage to PWB or injury to self FUNCTION CHECK JVC PROCEDURE INSPECT UNIT 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 TELEVISION CHECK PROCEDURMWG REQUIREMENTS FOR ON i sresv POW ASSY POW GOOD 1 AC line Voltage 2 Standby Voltage Circuit function 3 Power On Signal from Micon 4 In some models Main AC line voltage switch must be closed Provided all circuits function within a Power Supply there are only 3 or 4 requirements for the
31. t This circuit composes R911 R930 D911 and C914 This circuit Provi es the Start up Voltage for the Switching IC911 The DC voltage supplied by this circuit tums the IC and FET ON If the IC was open and AC current was allowed to flow no current would flow through the IC This would cause C914 to overcharge and explode For this reason If you find a defective Switching Regulator IC replace the Capacitor Similarly if you find exploded Capacitor replace the IC Reference Schematic 52004 Main PWB for Schematic Details TELEVISION SWITCHING DEVICE JVC TRANSFORMER CHARGING Current flows through the transformer and charges it A proportional voltage develops at the source resistor Turing the FET off will cause the switching action Reference Schematic 2004 Main PWB for Schematic Details 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 pin 3 The Voltage passed through the FET connects to a source resistor on to ground As the Transformer charges a proportional voltage will build on the Source Resistor R914 TELEVISION JVC SWITCHING DEVICE Turn Off 12 Applying 0 7V to Pin 1 will turn OFF the FET FET will turn on after pre determined time Do you remember this If0 7V is applied at pin 1 the FET turns OFF Due to the int
32. tle charge We must reduce energy transfer Some units utilize a Standby Mode 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 tum off the regulator In order to minimize the Power consumption we control the energy transfer by reducing the charging and discharging time Refer to the schematic and follow the standby supply for the CPU It is generated from the STBI3V TELEVISION SWITCHING OPERATION JVC STANDBY MODE GRAPHIC PM fe DEB N N N Stam ty In normal mode the on enm time is the transformer s charging time In standby mode additional DC added to the ramp X Tum on by Timon This reduces ramping time 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 This is done by raising the Ramp s base or adding DC to it The new ON Time will be the time it takes to ramp up to 0 7V from the additional DC TELEVISION SWITCHING OPERATION Jvc ADDITIONAL DC USING PHOTO COUPLER Additional DC is applied from IC s supply using a
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