How to troubleshoot Panasonic TH 42PX60U Plasma TV
9th Generation Plasma TVs troubleshooting
What really happens when the TV is plugged in.1. When the Plasma TV is plugged in, there’re a few indications of normal operation. Knowing this will help us understand what’s going on with the unit when an abnormality occurs. There is a click from the relays RL402 and RL403 when they are activated.
2. The LED in the Optical Jack inside the DT board turns on for approx. 4 seconds.
3. Immediately after that, one of the Tuner LEDs (Right) turns on (Solid Red) for approximately 20 seconds.
4. The LED in the Optical Jack inside the DT board turns on again for approx. 1 second and both LEDs (tuner and optical jack) turn off.
5. Then you will hear another click from the relays RL402 and RL403 indicating that they are no-longer engaged. (Note: At this time the Tuner and the Optical Jack LED turn off.)
Understanding how the SHUTDOWN circuit works
SOS
What will normally cause the TV to shut down?
A short circuit on any of the voltage lines> An over-voltage condition
> Abnormality in the Control Drive Pulse circuit (SC, SU, SD, and SS boards)
> Abnormality in the Control Drive Pulse circuit (SC, SU, SD, and SS boards)
Cases When Missing Voltages Can Cause the TV to Shut Down
Missing the source voltage to the PA board
(STB14V) from the P board
> Missing output voltage from the PA board to the DG board.
> Missing 15V or VSUS on either the SS or SC boards while the control drive pulses from the D board are being provided
If the SUB 5V, SUB 9V or MAIN 3.3V is missing on the DG Board, the unit goes into shutdown.
The power LED blinks ten times.
The voltages are monitored on the DG board by the MPU, IC1103
TV Shutdown due to Over-voltage or Short Circuit
This could happen if there’s a short circuit in one of the B+ lines from the PA board, an over-voltage condition, or missing STB 14V from the P board.
If any of the SUB or MAIN voltages that are highlighted on the DG Board is missing, the unit goes into shutdown.
The power LED blinks ten times.
If any of the voltages created on the PA Board is excessive or shorted, the unit goes into shutdown.
The power LED blinks ten times.
The base of Q5642 being low indicates a short circuit in the Main 1.8V, Main 9V, or Main 5V output of the PA board.
The base of Q5641 being low indicates a short circuit or an over-voltage condition in the NR14V, Main 1.8V, Main 3.3V, SUB 9V, SUB 3.3V or SUB 5V output of the PA board.
To rule out the P board (Use a Peak Hold Meter for voltage reading)
Follow this procedure when the click sound of the relay can be heard after the unit is plugged in. If the relay does not click, check the STB 5V from the P board.
If the STB 5V is missing, the P board may be defective. (If STB 5V is OK, the DG board may be defective.)
> Disconnect connector P10 in the P board (Make sure the TV is unplugged).
> Because you only have 2 to 3 seconds to measure the STB 14V, place your meter’s probe at pin 1 of connector P10 on the P board before plugging the TV to the AC line.
> Plug the TV to the AC line while still holding the probe at pin 1.
> Because you only have 2 to 3 seconds to measure the STB 14V, place your meter’s probe at pin 1 of connector P10 on the P board before plugging the TV to the AC line.
> Plug the TV to the AC line while still holding the probe at pin 1.
> Check to see if the 14V comes up. If it doesn’t come up, the P board is defective. If it does, (since it may take some involvement to determine which of the PA or the DG board is defective) it’s OK to order Both the DG and PA boards together.
Power LED blinks 10 times
When the power LED blinks 10 times right after the TV has been plugged-in into the AC line and the Power is OFF, the P, the PA, the DG, the H, or the DT may be defective.
Click on the pictures to magnify
To rule out the H board
Disconnect connector H40 and plug the TV into the AC line Note: If the Power LED stops blinking, the H board may be defective. If the power LED still blinks, (Keep in mind, every time the H board is suspected to be defective, change both the PA and the H board at the same time before applying power to the unit.)
> Remove the screws securing the DT board. Plug the TV into the AC line.
> Note: If the Power LED stops blinking, the DT board may be defective.
> Note: When the DT board is removed, the unit will power up with all functions disabled due to a lack of data communication.
> If the Power LED still blinks, it is possible that the problem is the PA or the DG board.
Power LED blinks 5 times
This is caused by abnormalities on the 5V line.
This could also happen if the VDA voltage is shorted.
SOS
> The Power LED could also blink 5 times if the VDA voltage is shorted [Normally by the Panel (de-multiplexer ICs)].
> To understand the reason,
> When the ribbon cables from the D board to the C boards are disconnected in order to isolate the C boards, the Power LED will blink 6 times.
> The following circuit explains the reason why.
> To properly isolate the C boards without having the Power LED blink, the test point TP9387 (Labeled TP9387 on the D board) should be grounded through a 1K resistor.
> The VDA connector should be also disconnected.
Drive Reset Circuit Test Point
The test point shown in these pictures is a substitute for TP9387. It is located on the foil side of the board. To make the ground connection, the board has to be removed.
Fan SOS
To determine if a fan is the cause of the 11 blinks of the power LED, simply use a peak-hold voltmeter to determine if pin 3 of the fan connector goes High before shutdown. If it does, the fan is defective. If it does not, check the other fans and the fan drive drive circuit.
D Board and DG board SOS Detect
No video, No OSD
Determining whether a No video, No OSD symptom is caused by the video process or the panel drive circuit
> Unplug the unit from the wall outlet.
> Disconnect the connector DG5 from the DG board.
> Plug the unit into the wall outlet and turn on the power.
> If the unit displays a white screen, It is a video process problem.
> If the unit does not display a white screen, proceed to check the panel drive circuits.
> Disconnect the connector DG5 from the DG board.
> Plug the unit into the wall outlet and turn on the power.
> If the unit displays a white screen, It is a video process problem.
> If the unit does not display a white screen, proceed to check the panel drive circuits.
Isolation of the SC and SS Boards
If any of the connectors providing the 15V or VSUS voltage to the SC or SS board is disconnected while the connectors that provide the Scan and Sustain Drive pulses from the D board are still connected, the TV will shut down.
[Do not let the TV run for more than 30 seconds while isolating any of the circuit boards.]
The Scan Board (SC) and the Sustain (SS) board could be easily isolated.
This can be useful to diagnose:
> Shutdown Problems
> Video Problems.
The SC board could be isolated from the sources (Supplied Voltage & Scan Control Pulses)
SC board completely isolated from the sources (P and D boards)
Expectation when Isolating the SC Board
The Supplied voltage VSUS and 15V (SC2 & SC23) cannot be disconnected while the Scan Control pulses (SC20) are being supplied to the SC board. This will cause a shutdown condition.
If SC20 is disconnected while SC2 and SC23 are still connected
The Power turns ON (Black Picture – No OSD – Sound is OK, and there should be video out of the Monitor Jack))
SS LED is ON and SC LED is OFF
The Power turns ON (Black Picture – No OSD – Sound is OK, and there should be video out of the Monitor Jack))
SS LED is ON and SC LED is OFF
Isolation of the SC Board
The SC board could be isolated from the Driver Boards (SU &SD)
Sometimes the TV goes into “Shutdown” indicating that the problem is located on the SC board. This does not
necessarily means that the SC board is the cause of the problem.
When this occurs, disconnect both the SU and the SD boards from the SC board.
Note: To disconnect, remove 2 screws holding each of these boards in place and disconnect SC41, SU45, SD46 and SC42
Isolation of the SC Board
Sometimes the TV may not go into “Shutdown” when there is a scan problem.
This symptom seems to be caused by a defective D or SC board. When in reality, it is caused by the SU board
This symptom seems to be caused by a defective D or SC board. When in reality, it is caused by the SU board
When this occurs, disconnect the SU board from the SC board.
Note To disconnect, remove 2 screws holding the boards in place and disconnect SC41, SU45.
Disconnecting the SU board yields a good picture at the bottom half of the screen and a completely black area in the upper half of the screen.
Isolation of the SU Board
What is the cause of this symptom?
How do you isolate a problem of this kind
How do you isolate a problem of this kind
Isolation of the SD Board
Supply Voltage from P to SS board
To completely isolate the SS board
> Disconnect P12 and P11 on the P board and SS23 on the SS board.
> Place a jumper at pin 8 and 10 of connector P12.
To completely isolate the SS board
> Disconnect P12 and P11 on the P board and SS23 on the SS board.
> Place a jumper at pin 8 and 10 of connector P12.
No output to SS board from the D board
Defective D board
Defective SC board
