Tuesday, January 12, 2016

SAMSUNG PS42D5S Troubleshooting - Power supply working – SMPS Voltages - No Power - No sound - Relay Chattering - Plasma television Repair and Service

Category: Plasma Television Repair and Service 

Contents of this article 

  • Troubleshooting 
  • SMPS power supply Working
  • SMPS power supply Voltages 


First Checklist for Troubleshooting
1. Check the various cable connections first.
# Check to see if there is a burnt or damaged cable.
# Check to see if there is a disconnected cable connection or a connection is too loose.
# Check to see if the cables are connected according to the connection diagram.
2. Check the power input to the Video Board.
3. Check the voltage in and out between the SMPS
> Video Board, between the SMPS > X, Y Drive Board, and between the Logic Boards.
No Power
# The LEDs on the front panel do not work when connecting the power cord.
# The SMPS relay does not work when connecting the power cord.
# The power of the unit seems to be out of order.
Check Points
The SMPS relay or the LEDs on the front panel do not work when connecting the power cord if the cables are improperly
connected or the Video Board or SMPS is out of order. In this case, check the following:
# Check the internal cable connection status inside the unit.
# Check the fuses of each part.
# Check the output voltage of SMPS.
# Replace the Video Board.
When the unit is repeatedly turned on and off
# The SMPS relay is repeatedly turned on and off.
Check Points
In general, the SMPS relay repeatedly turns on and off by the protection function due to a defect on a board connected to the SMPS.
# Disconnect all cables from the SMPS, operate the SMPS alone and check if the SMPS works properly and if each voltage output is correct.
# If the symptom continues even when SMPS is operated alone, replace the SMPS.
# If the symptom is not observed when operating the SMPS alone, find any defective ASSYs by connecting the cables one by one.
No Picture (When audio is normal)
# Audio is normal but no picture is displayed on the screen.
Check Points
# This may happen when the Video Board is normal but the X, Y Drive Board, Logic Board, or Y Buffer Board is out of order.
# The output voltage of the Main SMPS or the DC-DC SMPS is out of order.
# This may happen when the LVDS cable connecting the Main Board and the Logic Board is disconnected.
No Sound
Video is normal but there is no sound.
Check points
# When the speaker connectors are disconnected or damaged.
# When the sound processing part of the Video Board is out of order.
# Speaker defect.
# When setting the volume to 0 (Nonsense).

Circuit Description
1. Outline (PDP 42inch/50inch SMPS)
Considering various related conditions, the switching regulator with good efficiency and allowing for its small size and light weight was used as the power supply for PDP 42inch(Schubert)/50inch(Strauss), VS requiring high power consumption Asymmetrical Half Bridge converter and flyback converter. To comply with the international harmonics standards and improve the power factor, active PFC(Power Factor Correction) was used to rectify AC input into +400V DC output, which in turns used as input to the switching regulator.
2. Input
The power supply shall be capable of supplying full rated output power over free voltage ranges that are rated 100 VAC - 240 VAC RMS nominal. Operating voltage : 90 VAC - 264 VAC.
The power supply must be able to start up under peak loading at 90V AC. The power supply shall automatically recover from AC power loss. (Note that nominal voltages for test purposes are considered to be with +/- 1.0V of nominal). STD_5V & Vpr2(3.3V) is a SELV standby voltage that is always present when AC mains voltage present.
3. Output
Output Name
Output Voltage
Output Current(Max
+190V ~ 220V (210V)
+60V ~ 80V (70V)
4. Over Voltage Protection
The over voltage sense circuitry and reference shall reside in package that are separate and distinct from the regulator control circuitry and reference. No single point fault shall be able to cause a sustained over voltage condition on any of all outputs.
5. Short Circuit and Over current Protection
An output short circuit is defined as output impedance of less than 300mohms. The power supply shall shutdown and latch off for shorting VS DC rails to return. Shorts between main output rails and STD_5V shall not cause any damages to the power supply. The power supply shall either shutdown and latch off for shorting is removed, the P/S shall recover. The power supply shall be capable of withstanding a continuous short-circuit to the output without damage or over stress to the unit.