When a Samsung Smart TV begins freezing on startup, refusing to detect HDMI devices, showing a black screen while sound continues, or ignoring every press of the remote, the most common root cause is main board failure. Modern Samsung televisions rely heavily on this board for nearly all internal communication, and when it begins to malfunction, the symptoms can spread across several features at once. One of the most frequently replaced boards in Samsung’s lineup is the BN94-18351W, a part typically used in the Samsung QN77S90DAFXZA.
Below is a picture of the part in question:
Before beginning disassembly, many DIYers prefer a visual walkthrough. You can watch our helpful YouTube video below on getting started with main board repair:
Changed your main board already, but having problems with the picture? Watch our helpful YouTube video below on formatting your newly installed Samsung main board:
Why the Samsung BN94-18351W Main Board Is Important
The BN94-18351W serves as the central processing hub for vital operations in supported Samsung models. It manages video signal processing, HDMI input control, smart system software, audio distribution, and the communication pathway between the TV’s logic systems and its display-related components. When this board fails, the TV may still turn on, but essential functions will begin to break down. In many cases, replacing the BN94-18351W restores full functionality without the need for a new television.
Key Signs the BN94-18351W May Be Failing
Main board failure often develops gradually. When the BN94-18351W is starting to go out, you may observe issues such as:
The TV powers on but shows no picture, sometimes with audio still functioning.
HDMI ports fail to recognize devices or repeatedly drop signal during use.
The remote control becomes sluggish or non-responsive.
Smart apps freeze, crash, or become stuck at the loading screen.
The TV reboots at random intervals or remains stuck on the Samsung logo.
These symptoms are especially common in televisions using part number BN94-18351W, including the QN77S90DAFXZA.
Initial Troubleshooting: Always Start With a Reset
Many potential software-related glitches can be ruled out with a proper power reset. Use the following method before opening your TV:
Unplug the television from the wall outlet.
Press and hold the physical power button on the TV for 30 seconds.
Leave the TV unplugged for a minimum of 60 seconds.
Plug it back in and power it on.
If HDMI recognition problems, startup freezes, or app loading failures continue after a reset, the BN94-18351W main board becomes the primary suspect.
Distinguishing Main Board Failures From Other Issues
Correct diagnosis saves time and prevents unnecessary part orders. Understanding how symptoms relate to specific components is essential:
A black screen with working audio can point to either the main board or T-Con board.
Smart feature failure, HDMI issues, system crashing, or OS freezes almost always indicate the main board.
No power or no standby light generally reflects a power supply problem.
TVpartsToday Tip: Perform the flashlight test. Shine a light at close range onto the screen in a dark room. If you can see faint images, your backlights are likely the issue. If there is sound but no image during the flashlight test, consider the T-Con. If the TV has no sound, no image, and no system response, the main board should be examined first.
For a full walkthrough of the flashlight test, we offer a detailed guide on our website.
Matching the Correct Part Number
Samsung main boards cannot be selected by model alone. Identical TV models frequently include variations in internal components depending on the manufacturing batch. For the BN94-18351W, the correct number will appear on a sticker with a barcode or QR code on the board itself.
Avoid using numbers printed directly on the circuit board. Those are internal production codes and do not confirm compatibility.
TVpartsToday Tip: Always match the BN94-18351W part number exactly as printed on the sticker. When in doubt, send a photo to our support team. We verify part numbers for customers every day, usually within seconds.
How to Replace the BN94-18351W Main Board
For DIY repair enthusiasts, replacing the main board is one of the most accessible television repairs. Follow these safe steps:
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Unplug your Samsung TV and place it face-down on a padded, clean surface.
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Remove all screws securing the rear panel, then lift it away.
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Identify the BN94-18351W board by locating the cluster of HDMI and USB ports.
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Take reference photos of cable locations to avoid incorrect placement later.
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Disconnect all ribbon cables and connectors attached to the board.
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Remove the mounting screws holding the board in place.
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Position the replacement board, secure it with screws, and reconnect each cable carefully.
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Reinstall the back panel, plug in the TV, and power it on.
TVpartsToday Tip: If the TV boots up but displays unusual colors or missing picture modes, navigate to your picture and system settings. Some configurations may need to be restored after a main board replacement.
Why DIY Replacement Makes Sense
The BN94-18351W Samsung main board is one of the most frequently replaced parts in Samsung’s current lineup, especially in the QN77S90DAFXZA model. When your television shows persistent black screen issues, fails to recognize HDMI devices, freezes during startup, or continually crashes, replacing the main board is often the fastest and most cost-effective solution.
Repairing your TV instead of replacing it saves money and prevents unnecessary electronic waste. With the right part and a bit of guidance, most users can successfully complete this repair at home.
If you ever need confirmation before ordering, simply send us a photo of your board’s label. The team at TVpartsToday is always here to help ensure you receive the exact BN94-18351W you need.
Need Help?
If you’re still unsure about the issue or need to replace a part, reach out to TVpartsToday. We can help you identify the exact cause of the problem and provide the right replacement part!
Would you rather watch a video? Check out our helpful Troubleshooting 101 playlist over on YouTube!
Would you rather chat with a seasoned repair expert? Head on over to our TVRepairHelp subReddit!
Need help finding the right board or part?
Call us at 930-212-1975 or browse our inventory online.
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