Chosen Solution

Samsung model UN70NU6900FXZA flashes two times. Acts like it wants to start then shuts back off then repeats. TV is only 2 years old.

@ronwilliams do not switch any cables around unless you know that each wire connects each pin properly. Samsung does not use error codes so the 2 blinks is a bit of a dead end. Disconnect the main board from the power board and see if that changes anything. It does sound like a bad power board. Get a multimeter and check the voltages on the connector leading from the power board to the main board. Post some good pictures of your boards with your QUESTION so that we can see what you see. BTW I haven’t seen blown caps on Samsung power supplies for a few years now so it is no longer the number one cause for failed PSU’s. Adding images to an existing question - iFixit Repair Guide Update (08/31/2022) @ronwilliams835 Awesome. Thanks for the pictures. Okay so you will have to check the connector (CNM801) Use the voltage legend for that to determine what measurements you should get on what point. Number 1 contact is the one that has the arrow on it. See if you can follow this and can measure it:

  1. Power TV On √ POWER ON/OFF .2Vdc (when off) changes to 3.3Vdc (on) NOTE • There is an approx 20 second delay from PS-ON to off condition when the TV is powered off, and approx a 2 minute delay when the TV is first plugged into AC Power.
  2. If voltage error or no change: √Jog Function Control Test
  3. If OK replace Main Board √ All A13V supplies for approx. 12.7VDC (see SMPS label)
  4. If any wrong voltages, remove SMPS connector to Main Board √ All A13V again for 12.7VDC (see SMPS STBY/ON label)
  5. If OK replace Main Board
  6. If still wrong voltage replace SMPS √ OD_ ON/OFF (Over Voltage Detect) 3.3Vdc : Operating Normal
  7. If 0V or changing, an SMPS or Panel error exists. Perform Backlight Test. √ BLU_PWM Backlight On/Off & Dim Control: 1Vdc – 3.3 Vdc depending on backlight dimming level for video. • If missing or error : Replace Main Board. Update (08/31/2022) @ronwilliams835 okay so here is something interesting I found (and it’s a first for Samsung for me). After TV is “COLD BOOTED” (AC Power Re-Cycled), Flashing symptom codes will operate and show the defect block with a number of LED flash. It’s the Standby LED that does the flashing. To COLD BOOT the TV • Method 1) Unplug and re-plug in the power cord. • Method 2) While TV is on, Press & Hold Power Button of TV remote for 4 seconds. TV will turn off and on by itself. then the Standby LED will flash. If you get the 2 flashes for 5 times it lists the PANEL as defective. That would be no good! See what you find.