LG OLED TV How to check the SMPS (power supply board) of 2015 EF Series 

 

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LG55EF9500, LG65EF9500 - OLED TV power supply board (SMPS) testing procedure

When servicing an OLED TV and you need to Test the Power Supply, due to the symptoms the TV Won’t Come On or TV Intermittent Powers Off, before beginning the Power Supply Testing READ THE BELOW FIRST.

Read First Before Beginning the Power Supply Testing Procedure

Check the Front Power Indicator:

Take note of the front Power LED. If it begins to “Blink” (about once a second) continually for 30 seconds and the TV makes no attempt to turn on. 

It means that the Main board is “Latched” and no functions work.

If this happens, the Main board will not function again normally until it is unlatched even if the Main board is placed in another identical OLED model.

To Unlatch the Main Board:

Press the “Power Only” button using the Service Remote. 

This will place the TV into P-Only mode. 

P-Only = TV comes on in Full White Raster. 

A P-Only black box with text appears in the upper left hand side of the screen. 

P-Only mode will also bypass the “Burn Det” circuit _ , y which will allow the TV to turn on normally.

If the TV Comes on Normally in P-Only Mode:

Press Exit on any remote and the screen is not full white raster. 

Press the “In-Start” button (at the service remote control for LG), and enter the Service Menu. 

NB: You should have a special remote control "Service remote control" to enter the service mode of most models of LG TVs. There is no other ways to enter the service mode of these sets. You have to press the "Instart" button on the service remote control to enter the service mode. 

Scroll down to “Power_Off_History” and look at the events that shut off the TV. If you find three consecutive “INV_ERROR” this indicates activation of the Burn_Det circuit which is what “Latched” the Main board. If this is the case, look f S f “ or the Service Bulletin for this model; “Improved Auto Power Off / No Power issue”. This bulletin requires you to update the Software via USB only.

If the TV Still Won’t Come On:

In this case follow the Power Supply Testing, check the Main board. If both are OK, replace the Panel.

If the OLED TV Shuts Off Intermittently:

With the OLED turned on, press the “In-Start” button at the Service remote control, to enter the Service Menu. 

Scroll down to “Power_Off_History” and look at the events that shut the TV off. 

If you find PWR_OFF_by_20V_DET or PWR_OFF_by_INV_ERROR”, look for the Service Bulletin for this model; “Improved Auto Power Off / No Power issue”. This bulletin requires you to update the Software via USB only.

If the TV Still Continues to Intermittently Shut Off:

In this case follow the Power Supply Testing, check the Main board. If both are OK, replace the Panel.

LG (OLED EF Series) Power Supply Board 12V/24V to Main Voltage Check

AC Should not be applied at any time while adding jumpers or While unplugging connectors, damage to the circuit Board may occur.

When AC is applied, the SMPS “MUST” be producing STBY 3.5V (3.52V) on pins 5 and 7, 8 of P201.

If 3 5V Standby is not being generated, the SMPS is defective and may need to be replaced. Make sure AC is arriving at the connector SK100 and +3.5V_ST is not loaded down by the Main Board or the Joy Stick/IR Board.
Remove connector on Main board. If STBY is still missing, SMPS is defective.

II) Unplug P2399 on the Main Board to make insertion of the Jumpers easier Use P2399 side to insert jumpers.

TESTING THE POWER SUPPLY TURN-ON CIRCUIT.

Add a jumper (A) between (3 5V STBY) pin 5 and (PWR ON) Pin 1

Apply AC, this will turn on the SMPS. Relay click will be heard

Check that the 24V and 12V power supplies to the Main board are turned on,

To Main Board Power:

 P201 (11.96V pins 11-15)
 P201 (23 70V pins 19 22)

No 12V or 24V to T-CON at this time.

Remove AC power

Pin 1 is Bottom on SMPS
Pin 1 is Top on Main

To Test the Power Supply’s T CON 12V line

Continue if Test 1 was OK.
Leave original jumper (A) in place.

AC Power is removed at this time.
The T-CON should be connected, SMPS P202 and P203 to T-CON

Add another jumper (B) between (STBY_3.5V) pin 8 and (12V_ON) Pin 18.

Simulating PWR_ON and 12V_ON commands.

Apply AC Power.

Check 12V (11.87V) on pins 7-12 on P202

T-CON 12V Normal:
a) If normal, the SMPS is OK, T-CON 12V load test OK

T-CON 12V Abnormal:
a) Recheck all connections.
b) Confirm the 12V_ON line pulling up to at least 3V.
c) Check SMPS P202 pins 7-12 for an excessive load, normal diode check  should be 0.48V P202 connected “0.50V” P203 disconnected.

Check CN11 pins 8-12 on the T-CON for an excessive load.
Diode check should be “1.04V”. (CN11 unplugged from the SMPS, the panel can be connected or disconnected).
Note: With Red lead on Chassis ground, reading is 0.41V.

If you are concerned that you may accidently connect the jumpers in the incorrect locations use a 100 ohm 1/8W resistor instead.

Leave jumpers (A) and (B) in place. AC Power is removed at this time.

The T-CON should be connected, SMPS P202 and P203 to T-CON

T-CON 24V POWER SECTION TEST:

Add another jumper between (STBY_3.5V) pin 5 and (DRV_ON) Pin 2.

Simulating PWR_ON, DRV_ON and 12V_ON command.

Apply AC Power.

Check 24V on pins 8-14 on P203

T-CON 24V Normal:
a) If normal (24.16V), the SMPS is OK, T-CON load test OK

T-CON 24V Abnormal

a) Recheck all connections.
b) Confirm the DRV_ON line pulling up to at least 3V.
c) Check SMPS P203 pins 8-14 for an excessive load, diode check should be “0.48V” P203 connected or disconnected.

Check CN5 pins 8-14 on the T-CON for an excessive load.

(CN5 unplugged from the SMPS, Panel connected). Diode check should be “OL” (Blk lead on Gnd) 0.38V (Red lead on Gnd).

(CN5 unplugged from the SMPS, Panel disconnected). Diode check should be “OL” (Blk lead on Gnd) 0.51V (Red lead on Gnd).

To Test the Power Supply’s T-CON 24V line using a light bulb test jig

In this case, the Power Supply needs to be tested to see if it can supply the T-CON 24V and 12V when loaded.
TEST 4: (2015 EF Series OLED) Power Supply Board T-CON 12V and 24V Power
TEST 4: 24V T-CON POWER LOAD CHECK:
 Leave all Jumpers in place on P2399 to P201 of the Power Supply and disconnect CN5 on the T-CON board.
 Make a 24V load test jig by using a standard 1157 automobile light bulb, (dual element). Solder two wires from the buttons on the bottom of the bulb. Do not solder any wire to the actual ground of the bulb.

Attach one end of the Jig to the 24V line from P203 pins 8-15 from the SMPS.

Attach the other wire from the Jig to Chassis Ground.

To make insertion easy, cut the sharp end of a safety pin off and solder it to each end of the wires coming from the light bulb Jig.
Push one needle end into one of the pins 8-14 of CN5.
Push the other needle end of the wire into any pin 1-7 of CN5.

Apply AC to the power supply, the light bulb should light and remain lit.

Measure the 24V line to confirm it’s correct. The bulb should be bright.
Let the SMPS run for several minutes to confirm its operating correctly.
(Do not let wires or light bulb touch any metal parts).
Note: You can also use two sing ( le element automotive bulbs (each 6W) tied in series.
a: If the Light Bulb remains lit, the panel is defective because the T-CON and/or the panel is providing too much of a load causing the power supply to shut off.
b: If the SMPS shuts off, Replace the Power Supply.
TEST 5: 12V T-CON POWER LOAD CHECK:
Note: You can test the 12V to the T-CON line using the same procedure, but you only need one bulb. Use same bulb, but solder one lead to a button and the other to the case.