On Tuesday, March 5, 2013 8:13:58 AM UTC-5, Sparkey wrote:
Hi;



This is a Vizio M420NV.

Backlight was out, I found an open 3A fuse (TF1) on the main board that carries 12.4 vdc. When fuse replaced, the backlight will flash a couple of times and poof goes the fuse again.



I don't have a diagram. I wonder if this might be due to a inverter fault ?

I checked power transistors on main and power supply board.

Any ideas ?



Thanks,

The fuse for the 12V feed to the main does not cover the inverter B+, that's fed directly from the smps to the inverter board(s) and fused at that end.. The inverter was blinking because the main is gimpy..

If the 12V fuse on the main is opening, you most likely have a shorted regulator IC on the main, and possibly an IC after that drawing and overheating the regulator. Unfortunately, Vizio is loathe to provide any service information on their boards. You're best bet at this point is to replace the main. Make sure you get the correct one as there are typically several versions for the same model to match the display\tcon.