there's a weird high-pitched buzzing sound coming from the back of the tv, even when it's off.

Diagnosis

The high-pitched buzzing or "whining" sound emanating from the rear of your Roku TV 43-inch Select Series is a phenomenon known as coil whine. This occurs within the Switch Mode Power Supply (SMPS) board. Specifically, the electricity passing through the inductors and transformers creates a magnetic field that causes the copper wire coils to vibrate physically. When these vibrations happen at a frequency audible to the human ear, you hear a piercing, high-pitched drone. Because this is a "Smart" TV, the unit is never truly "off" when plugged in; it remains in a standby state to listen for the remote control signal and maintain network connectivity. This constant trickle of current keeps the power board active, which is why the noise persists even when the screen is dark. You can confirm this is coil whine by placing your ear near the bottom-left or bottom-right rear vents; the sound will be most intense near the power input section of the internal chassis. If the pitch changes slightly when you wake the TV from standby, it confirms the noise is tied to the voltage load on the capacitors and inductors.

How to Fix It

While coil whine is often a hardware characteristic, you can frequently mitigate the intensity by stabilizing the electrical input and resetting the power rail. Follow these exact steps:

1. Perform a Hard Power Cycle: Unplug the TV from the wall outlet completely. While it is unplugged, press and hold the physical power button on the TV chassis for 30 seconds to drain the remaining charge from the capacitors on the power board.
2. Bypass Power Strips: Disconnect the TV from any surge protectors, power strips, or extension cords. These devices can introduce electrical noise or "dirty power" that exacerbates coil vibration. Plug the TV directly into a grounded 120V AC wall outlet.
3. Isolate the Circuit: If possible, plug the TV into a different circuit in your home. High-draw appliances (like a refrigerator or space heater) on the same circuit can cause voltage fluctuations that trigger the buzzing.
4. Disable Fast Boot/Quick Start: Navigate to Settings > System > Power. If your specific firmware version allows for a "Deep Sleep" or "Energy Saving" mode, enable it to reduce the current draw during standby.

If That Didn't Work

If the noise persists after stabilizing the power source, you are dealing with a physical resonance issue that cannot be fixed via software. Try these alternatives:

• Relocate the TV: Move the TV 2-3 inches further away from the wall. When the TV is pushed tight against a wall, the wall acts as a sounding board, amplifying the high-frequency vibrations and making the buzz seem louder than it actually is.
• Check for Interference: Move any wireless routers, baby monitors, or high-powered speakers at least 3 feet away from the back of the TV. Electromagnetic interference (EMI) from other devices can occasionally excite the coils in the power supply, increasing the audible whine.
• Apply Dielectric Silicone: For advanced users comfortable opening the chassis (and who have voided their warranty), the noise is caused by a loose coil winding. Applying a small bead of non-conductive, high-temperature electronic-grade silicone glue to the vibrating inductor on the power board can dampen the physical vibration and silence the noise.
• Replace the Power Board: If the noise is accompanied by a flickering screen or the TV failing to wake from standby, the inductor may be failing. Replace the internal power supply board (Part number varies by production date, check the sticker on the board itself) to resolve the issue permanently.

Heads Up

• Safety Warning: Never open the back panel of the TV while it is plugged in. The capacitors on the power board hold a lethal electrical charge even after the unit is unplugged.
• Warranty Note: Opening the chassis to apply dampening glue or replace boards will void your manufacturer warranty. If the TV is under a year old, contact support for a replacement.
• Normal Operation: In most cases, coil whine is a cosmetic annoyance and does not indicate that the TV is about to fail or that there is a fire hazard.
• Power Quality: If you live in an area with frequent brownouts or voltage spikes, consider a high-quality Pure Sine Wave UPS (Uninterruptible Power Supply) to clean the incoming current.