the power light just blinks red 3 times and the tv won't turn on at all

Diagnosis

The three-blink red sequence on the LG 43UR7300PSA is a specific hardware fault indicator signaling a failure in the Power Management circuit. This occurs when the main logic board attempts to initiate the "Power-On" sequence, but the Power Supply Unit (PSU) fails to provide the required stable DC voltage (typically the 12V or 24V rail) to the processor. Because the system detects a voltage drop or a short circuit, it triggers a protective shutdown to prevent the motherboard from frying, resulting in the rhythmic three-blink error code. This is frequently caused by "leaky" or bulging electrolytic capacitors on the PSU board that can no longer hold a charge, or a failure in the standby voltage circuit. In some cases, it is a "phantom" error caused by residual static charge buildup in the capacitors, which prevents the handshake between the main board and the power board. You can confirm this is a power-rail issue if the TV remains unresponsive to the physical power button on the underside of the bezel, not just the remote control.

How to Fix It

To resolve a soft-lock or capacitor discharge issue, follow this precise hard-reset sequence:

1. Disconnect the power cable from the back of the LG 43UR7300PSA and unplug it from the wall outlet entirely.
2. Locate the physical power button located on the bottom center/underside of the TV frame. Press and hold this button down for a full 60 seconds. This drains the residual electricity from the capacitors on the main board.
3. Bypass any surge protectors, extension cords, or UPS units. Plug the TV power cord directly into a known-working 120V/240V wall outlet to ensure the PSU is receiving full, unfiltered amperage.
4. Wait 10 minutes before plugging the TV back in. This allows the internal components to thermally stabilize.
5. Power the unit on. If the TV boots, immediately go to Settings > General > Device Self Diagnosis to check for system errors.

If That Didn't Work

• Test for Backlight Failure: Shine a high-intensity flashlight directly against the screen while the TV is "on" (blinking). If you can see a faint image of the LG logo or a menu, the PSU is working, but the LED backlight driver has failed. This requires replacing the LED strips or the backlight inverter circuit.
• Reseat Internal Ribbon Cables: If you are comfortable opening the chassis, remove the back cover and locate the wide ribbon cables connecting the PSU to the Main Board. Unplug and re-insert these cables to clear any oxidation or loose connections that may be causing a voltage drop.
• Replace the Power Supply Unit (PSU): If the blinks persist, the PSU board (Part No. typically found on the board label) has failed. You will need to replace the entire board. Ensure the replacement board matches the exact revision number of your 43UR7300PSA model to avoid voltage mismatches.
• Main Board Replacement: If a new PSU does not stop the 3-blink code, the fault lies in the Main Logic Board's power management IC. This is a more expensive repair and involves replacing the central processing board.

Heads Up

• Voltage Warning: Never touch the large primary capacitors on the PSU board even when unplugged; they can hold a lethal charge of 400V+ for several minutes.
• Power Strip Hazards: High-resolution 4K TVs like the UR7300 series are sensitive to voltage sags. Using a low-quality power strip can trigger the 3-blink protection mode.
• Ventilation: Ensure there is at least 2 inches of clearance around the rear vents. Overheating the PSU is the primary cause of capacitor failure in the 43-inch series.
• Firmware Updates: Once the TV is back online, update to the latest webOS version immediately, as LG often releases stability patches for power-sequencing bugs.