HITACHI - PLASMA TV DW3s - TROUBLESHOOTING

                                                              
FAULT:  NO PICTURE
Reasons

1. The power supply may not be producing the correct voltages.
2. The Digital Module may not be producing correct Turn-On command s [Power-1 & Power-2]
3. The Logic PWB may not be supplying the correct Vs/Va Turn-On commands.
4. The Panel shorted.
5. The panel is defective, but not presenting short.
6. Y-SUS and or X-SUS may be defective. [Shorted or non-working]

Monitor the front panel Power LED.

• Does it turn ON, and then go OFF completely (Indicates shut-down).  Power supply is not running.  (Might be due to a short circuit).
• Does it Turn On and stay Green, but No picture.  No shut-down.
• power supply running basic power supplies, but Vs/Va voltages are not present.

Observations [Power supply]

• Look carefully around all mounting screws for cracks or PWB damage.
• BUFFERS (Drivers) on SDR Upper and/or lower PWBs [50" to 60"]

Carefully observe the Buffer "Snot" Chips.  Left side black chips mounted on the SDR upper and lower PWBs.  Check very closely for burns and/or small holes in these chips.  If any defect is noted, make sure that the PWB is defective.  Replace it and the Y-SUS if PWB is not upgraded.  Replace only SDR if PWB id upgraded.

COF [Chip On Film] from panel to A-Bus [42"]  Carefully observe the COFs (mounted on the flexible ribbon cables).  Look very closely for burns and/or small holes in these chips.

Check whether any ribbon cable damage on the connections to the Panel itself from the A-BUS PWBs.  If any defect noted, the panel is defective.  Some additional dis-assembly is required to see thes COFs as they are on the under side of the ribbon cable coming from the panel to A-BUS L, R and C PWBs.

 

 

Hitachi Plasma TV Power Supply troubleshooting

                                                                       
PWB CHECK

• Look for any burns, open fuses etc:  
• If burns found, replace the PCB as card basis.  It in not practical to make a repair to this board.

VOLTAGE CHECK

• When AC is first applied, the power supply should turn ON and supply the following voltages.
• Standby voltages [SBY 5V], SBY 3.3V on some models] and all voltages on the CNPSS connector.  
• This requires Power-1 and Power-2 commands being high coming from the Dig-Main PWB CN-63.  After approx: two minutes, unless quick start is ON, a relay click is heard and the CNPPS voltages turn OFF.
• If quick start is ON, power 1 & 2 commands remain high and all above voltages remain ON.

WHEN THE POWER BUTTON IS PRESSED:  

When the power button is pressed, the logic PWB sends Vsago and Vcego commands to the power supply; via CN64 connector.

• There are two conditions the set can be in before the power button is pressed.

1. If quick start is OFF, the Power-1  and Power-2 commands are output from the Digi-Main PWB after a short internal self diagnosis is run.
2. If quick start is ON, the above stated does not happen because, Power-1 & 2 commands are already high, 'When AC is first applied'.

• Generating the Vs and Va voltages?  This requires the  Vcego & Vsago commands being high coming  from the logic PWB CN-68 connector.

For a 42"

• Va-CN64 pin number-1
• Vs- [85v] CN64 pin number-7
• -Vs-[-85.8v] CN 64 pin number 9 (For newer DW-3 chassis)

For a 50"

• Va-[60V] CN64 pin number-1
• Vs-[80V] CN64 pins 8/9/10

COMMON CONDITIONS 2&3 BELOW IN THE DW-3 SERIES

• Any time Vs of Va voltages do not appear and a test is made, each time a new test to be made.
• Press the Power button and turn the Plasma Off.
• Wait until a click of relay is heard.
• Unplug CN64 connector.
• Re-plug the CN64 connector.  
• If this is not done, the turn ON command for Vs/Va at pins 7&8 of the CN68 connector will not happen.
• If the connector CN68 is pulled and voltage readings are taken on the CN68 connector at power supply the STB 3.3V will be present at pin-3.  There will be no voltage at pin-1.

P50H401 POWER SUPPLY REGULATOR BOARD

 

Hitachi Plasma TV Troubleshooting

                                                                    
FAULTS

• The green power LED is always ON.
• The  power LED will go green  and may go Off or stay ON.
• Green power LED will go green then go Off or may not go green at all.

THE GREEN POWER LED IS ALWAYS ON

• This indicates that the set is providing Vs and Va voltage to the X-SUSTAIN & Y-SUSTAIN PWBs.  Use an analogue scope.  Look at the outputs from X-SUS and X-BUS.  Use the top pin of the connector going to panel, on either side.  
• No activity usually indcate with a defective PWB.
• Pull the ribbon cable from that PWB  to the panel, and check again.
• If there is activity now, the panel might be defective.  In most cases, it is.
• Pull all ribbon connectors before condemning the PWB.
• If the panel is defective, in most cases it can be seen by the panel itself.
• If Top ribbon cable is pulled, the top of the screen will be black; but the bottom will have raster.

GREEN POWER LED GO GREEN THEN GO OFF.  

• This indicates a load on the line.
• Pull CN64 connector feeding Vs and Va voltages to X-Sustain.
• Measure the resistance in [Ohms] from Va and Vs lines on each PWB.
• Low resistance value indicates a defective PWB. Normal reading should be of Mega-ohms. Using the diode mode on the DV/Voltmeter, there should be a brief charge time, then infinity.  Note, if there is a charge on the line, the meter may show low.  Pull the CN-68 connector and take the reading again.
• The line should now be infinity when reading the power supply pins for Va and Vs when reading the connector going to the X-SUSTAIN PWB.
• If a low is see on the connector , pull CN32 [bottom right hand plug on the Y-SUS board.

After the connector is pulled:

If low disappears, then the Y-SUS or SDR PWB has the fault.  If low remains, X-SUSTAIN is faulty

Pull all ribbon cables going to the panel, one by one while reading Vs/Va pins.  If the low disappears, the panel is defective.  Before confirm, check SDR buffer too.

If low remains the Y-SUSTAIN and/or SDR PWBs are defective.

                               

• If no evidence found:
• Does Vs & Va voltages stay up.
• If yes, Panel is defective.
• If No, in this case neither PWB can be confirmed as fault.  Suspect Y-SUSTAIN PWB.
• Disconnect the SDR Upper or Lower or Both from the Y-SUSTAIN PWB, and test Vs/Va voltages.  They must come On and stay up with these PWBs removed from the Y-SUSTAIN PWB.

IF THERE IS NO Vs/Va

• There must be a dead load on the line, or no Vsago/Vcego commands from teh Logic PWB CN68.
• Check the Va and Vs run-on commands.
• The SBY 5V from CN63 pin-1, must be present before Vsago/Vcego lines can function.  AS the Power button is pressed, [Vcc5.1V] should come when Vcego/Vsago.  Commands go high.

TESTING THE Vs & Va TURN ON COMMANDS

• Press the Master Power Switch on the bottom, to remove AC.
• Wait unitl a relay click is heard.
• Unplug CN68 connector, and re-plug it back.  If this is not done, Turn On command Vcego / Vasgo at pins 7&8 of CN 68 will not happen.
• Connect a DC voltmeter to the CN68 connector Vcego / Vsago.
• Press the vacation switch to apply AC power, and wait for about 30 seconds for initilization.  
• If Normal:  After several seconds, Vcego / Vsago voltages should reach to 3.3v.
• If a troubele is sensed, these pins will climb and then quickly drop the voltage to less than 0.03.

AFTER A TROUBLE SENSE

• Pull the CN64 connector.
• If the condition changes as described above, there is a load on Va/Vs lines.
• If the condition does not change, the the problem is with Logic PWB.  Carefully examine the connector from CN68 to the Logic PWB CN6
• Look for any visible damage to this cable.  
• Confirm SBY +5V from pin-1 of CN63.  There are no diagnostic LED on the Digi-Main PWB.

SOME POINTS TO NOTE WITH DW-3 POWER SUPPLY

• Generates standby 5V any time AC is applied to the power supply PWB.  No matter whether the set is turned On or Off.
• Digi-main PWB generates Power-1 and Power-2 commands on the CN63 connector when the set is in quick start, even when the set is Off and when the set is turned On.
• Generates all voltages of CNPPS connector, when the set is in quick start, because of Power-1 and Power-2 are high.  #  The TV turns on quickly. ## No data communication have to be re-initiated at turn on. ### The Sub-Digital PWB digital tuner can be on.
• Power-1 and Power-2 CN63 connector do not turn on Vs & Va or Vcc 5.1V, it only turns on the CNPPS voltages.
• Power-1 and power-2 CN68 connector comes from the Digi-Main PWB PPM1 connector.
• Vsago&Vsego CN 68 connector comes from the Logic PWB CN6 connector.
• The CN68 connector should be unplugged and then re-inserted to reset the power supply, if Vs of Va did not come up for any reason.  If this is not done, Vcego / Vsago will never attempt to turn on Va/Vs again.  If AC is removed, this will reset the power supply.  It will take over five minutes time.
• Power supply can be forced On to test all power supplies.  
• Vcc 5.1V at CN64 pin-3 and CN68 pin-1 is generated at the power supply and is output voltage from the power supply, and not an input.
• In Series-1 models, CNPPS pins7,13,14,15 all are tied together.
• In Series-2 models, CNPSS pins 13,14,15 are tied together.
• Vcc 5.1V, CN63 Pin-3 and CN68 pin-9 are tied together.
• Power-3 is not used [CN63 connector]
• The relays, RL001 & RL002 turn on any time AC is applied to power supply PWB; if quick start is Off, both relays turns off after a two minutes when AC is first applied.  If quick start is on, both relays stay on.  When the set is turned on, both relays turn on