Chosen Solution

I have a sony bravia kdl-40w605b. There is no picture but the sound works fine at least I can hear the beeps from the menu even though I cannot see it. The backlight is working fine. This would normally be put down to a t-con failure however there appears to be no dedicated t-con board. The t-con cable goes directly from the mainboard to the screen. I have replaced both the mainboard and t-con cable with no joy. Is there something I am missing? Could this be the power board or something else? Update. So new power board caused 6 red blinks so I’m guessing that I either got sold a duff board or it’s the wrong board despite having the same model number. Im including a picture of the boards now.

Update (09/08/2018) So I figured it out. I feel like an idiot

@thelazydj I would have measured the output from the power supply to the mainboard first. Remember that it is your main board that turns on the power supply etc. since you already replaced the main board and the cable, you only have the power supply left. Here is the Sony triage sheet for your TV model

It shows which boards are common failure based on your TV’s symptoms. You said you replaced the main board but did not tell us if your replacement included the tuner board. Sony part number A-1998-231-A. Post some images of the boards you replaced. Use this guide for that Adding images to an existing question

Most likely is the PSU. check visibly for leaking or bulging capacitor tops also if an ESR meter is available check for the series resistance of each capacitor . The PCB may have one or more dry joints…use a magnifier to check the board.

Check the connections on both ends of the T-con cable. This is a flat ribbon cable that goes to the panel. It is possible that the cable itself is defective. Also, verify that there is no picture on the screen using a flashlight. How do you know that the back light is working properly? Update this with the results of the above. Dan

Tcon board Also upon replacing boards you may get green and Amber flashing light which means it needs a update