PRIMA PS42D8 PLASMA SCREEN - FUNCTIONS OF VARIOUS MODULES - TROUBLES

PRIMA PS42D8 PLASMA SCREEN - FUNCTIONS OF VARIOUS MODULES - TROUBLES

MODULES & FUNCTIONS
PDP screen can be divided into power supply board, X driving board, Y driving board, logic board, logic BUFFER board (E, F, G), Y BUFFER board ( upper and lower), COF etc.:

• Power supply board: to supply power for the screen, other functional modules on the screen, our own main board, and video frequency processing board.
• X driving board: to produce and provide driving signal for X electrode according to the time sequence signal sent from logic board.
• Y driving board: to produce and provide driving signal for Y electrode according to the time sequence signal sent from logic board.
• Logic board:to process the image signal sent from the main board, to produce addressing signal and to provide driving signal for X and Y driving boards.
• Logic BUFFER board (E, F): To convert the data signal and control signal sent from the logic board into the signals required by COF
• Y BUFFER board (Upper, Lower): to transmit the scanning signal from the Y driving board to the screen, which is divided into upper and lower parts.
• COF: to convert the signal sent from the logic BUFFER board into the address signal used by the screen.

TROUBLE DIAGNOSIS

The screen is not bright:

• Check to see if the power supply plug from the power filter board to the power supply board is well inserted into the socket. If not, plug it in.
• Check if the fuse on the power supply board is blown up. If yes, replace it for a good one.
• Remove our main board and the video frequency processing board, ground the pin 4 POWER_ON/OFF of socket CN802 of the power supply board, and then push the slide switch SW2001 on the logic board to the internal modes (1, 3 up and 2, 4 down) from external modes (1, 2, 4 up and 3down).
• Switch the power on and see if the screen is lit. If the screen can give a normal and completely white field signal, then the problem lies in our main board or video frequency processing board, which will be dealt with separately.

• If the screen is not lit, then first replace the power supply board to see if the problem is solved.
• If the problem remains after the power supply board is replaced, then the problem lies in the screen. Replace the entire screen.

There appears on the screen a line or several unlit lines.

• Check if the socket between Y driving board and Y BUFFER is plugged well. If not, plug it well. If yes then replace Y BUFFER (upper, lower) in respect to the upper , lower part of the dark line on the screen.

There appear on the screen one or several horizontal lines that are much brighter than the remaining horizontal lines at the edge:

• Check if the socket between Y driving board and Y BUFFER is plugged well. If not, plug it well. If yes then replace Y BUFFER (upper, lower) in respect to the upper , lower part of the dark line on the screen.

There appear on the screen one vertical unlit line or a vertical entirely unlit block

• If it’s one vertical unlit line, then COF has problem.

• If it’s a vertical entirely unlit block, then first check if the connection socket between COF and logic BUFFER has problem. If not, check if the connection socket between the logic BUFFER and the logic board is normal. If yes, replace the logic BUFFER. Finally, if the problem still remains when the replacement is over, then replace the logic board. 

There appears on the screen a mono color signal and one or several vertical bright lines of other colors:

• If it’s a vertical bright line of other colors, then the problem lies with COF or the screen.

• If it’s an entire vertical block of other colors, then first check to see if the connection socket between COF and logic BUFFER has problem. If no problem, check if the connection sockets between the logic BUFFER and the logic board is normal. If it’s normal, then replace the logic BUFFER. If the problem still remains after the replacement, then replace the logic board. Finally if the problem is still there, then the problem lies with COF.

There appear on the screen abnormal bright spots or blocks that are different from what’s described above: 

• Check if the connection socket between COF and logic BUFFER board has been well plugged.
• Replace the logic BUFFER board. If it’s not solved then replace logic board. If the problem still remains, then it’s the problem with COF.

For Plasma TVs,  it is best to replace the damaged board with a new one, rather than try to repair it. Be sure to replace it with same part number used.  To some replacements, a software update might be necessary.  So be prepared for that too.