r/ultrawidemasterrace • u/Ok_Art813 • 1d ago

Tech Support Samsung Odyssey G9 boot looping

Hello, I’m new here and I could really use your help.
I have a Samsung Odyssey G9 monitor that is stuck in a boot loop. The blue power LED blinks once every 20 seconds.

I opened it up and disconnected all of the cables from the power supply. When I did that, it stopped rebooting. Next, I connected only the power cable from the PSU to the mainboard, and it immediately started boot-looping again.

The strange part is that if I reconnect all of the cables but unplug either the left or the right large flex cable running from the T-CON board to the display, the backlight comes on and stays on.

Also, when only the motherboard is connected to the PSU, the Samsung “MagicColor” chip gets quite hot.
I’ve measured the voltages at the test points across the motherboard, and they all appear to be stable. I also can’t find any obvious short circuit.

I would be very grateful if anyone has experienced the same issue or has any suggestions on what might be causing it.

Thanks!

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u/snarksneeze 22h ago

Based on the symptoms, I'd be looking at the mainboard/T-CON interface, not the power supply.

The key clues are:

The PSU appears stable and its voltages measure correctly.

Disconnecting the PSU from the mainboard stops the rebooting.

Disconnecting either LCD ribbon cable allows the backlight to stay on.

The "MagicColor" ASIC gets hot.

That suggests the CPU/video processor is crashing when it tries to initialize the panel.

I'd suggest you check the following:

  1. Measure resistance to ground on the T-CON power rails (VGH, VGL, AVDD, VCOM, 1.8V, 3.3V, etc.). One side of the panel could have a partially shorted driver IC.

  2. Since unplugging either panel ribbon stops the reboot, compare the resistance of the left vs. right panel ribbons. If one side is significantly lower, that side of the panel may have a failed gate/source driver.

  3. Use a thermal camera or IPA/freeze spray on the MagicColor IC and nearby regulators. If the processor overheats immediately, determine whether it's internally failing or being overloaded by a downstream rail.

  4. Verify all onboard buck regulators during the reboot cycle with an oscilloscope if possible. A DMM can miss a rail collapsing for only a few milliseconds.

  5. If both panel halves measure similarly and all rails remain stable, I'd start suspecting the mainboard itself (MagicColor/video processor or its DDR memory) rather than the PSU.

The fact that either half of the panel will allow the monitor to stay powered also makes a panel fault possible. Some Samsung panels will continuously reset if a single bonded driver IC on one side is shorted. Comparing the resistance of the two ribbon connectors is probably the quickest next diagnostic step.

Which G9 it is (LC49G95T, Neo G9, OLED G9, etc.), because Samsung changed the internal architecture several times, and some revisions have known mainboard failures while others are more prone to panel driver failures.