Samsung UN J5500AF Series Service Manual page 29

4. Troubleshooting
SMPS / Backlight Test
CM803
3 LED Strings Control
LED Pins
3-
3+
2-
2+
1-
1+
A
230Vdc (panel size dependent) BL Supply measured at diode Stripe(cathode). This will raise to approx 280Vdc
with an open string of LEDs.
1 Activate Backlights – Disconnect
2 Measure BL Supply voltage at 1+ or at the supply diode cathode (stripe).
Remove Panel connector and measure again to compare.
3
4
If voltage is high and stays the same high reading a string of Panel LEDs are open. Replace the Panel.
If the voltage is low and remains low the SMPS is defective.
4-8
Min B/L Max B/L
130Vdc 95Vdc
174Vdc 151Vdc
174Vdc 151Vdc
218Vdc 207Vdc
218Vdc 207Vdc
241Vdc 235Vdc
Simplified BACKLIGHTS Test
Lead Cable from Main to Power Supply.
230Vdc
A
Fixed Supply
Panel Con.
Full B/L Test
Removed
88Vdc
144Vdc
144Vdc
200Vdc
200Vdc
230Vdc 275Vdc
CNL802
Sample
2- open
0 0
0 0
0 Opened
0 257Vdc
0 257Vdc
279Vdc