KDL-70X4500 (serv.man3) - Sony TV Service Manual (repair manual). Page 19

KDL-70X4500 (K)     2-6

1) Power Error (R ED 2 tim es blink )

This indicates POWER Error, Low B error of 12V from G8 board. TV Micro (on AU board)
monitors pin79 and pin138 to detect POWER_ERR and shuts down chassis power to 
Standby status.

TV Micro pin138      Normal condition : Low  /   Error case : High
TV Micro pin79        i_lb_err< 0.7V(PW_ERR_LEV)

   - Check 12V at CN 1000 on AU board. And F1001 on AU has 12V or not.
   - Check G8 board.

2) T-CON  Error (R ED 5 tim es blink )

This indicates T-CON RDY signal error from timing controller of Panel module.
BE micro pin128 on FBU board detects it.

BE Micro pin128   Normal condition : High  /   Error case : Low

Replace Panel module.

3) B ack  Light Error (R ED 6 tim es blink )

This indicates panel power circuit error such as inverter.
BE micro pin 78 on FBU board detects it.

BE Micro pin 78   Normal condition : High  /   Error case : Low