Roberts MP53 Display Backlight Failure Repair Notes

[fixy88]

Some repair notes in case it helps someone else with this fault.
Roberts MP53 table radio had display characters visible but no backlight aside from a brief flash on power up. Upon disassembly and testing a faint backlight was visible and would flicker more brightly occasionally when adjusting backlight brightness in menu.

Backlight supply was traced to an LD1117A adjustable regulator marked IC7 on the main PCB and found to have an unstable and low output voltage. SMD resistors next to the regulator were tested and the 180 ohm found to be open circuit, the 560 ohm was ok. The 180 ohm resistor was replaced and backlight was restored. These resistors set the LD1117A output voltage at 5.16v when working correctly.

The brightness of the display backlight is adjusted by the main MCU controlling a nearby SMD transistor in series with the LED K line and ground.