Vizio vt420m no picture - Vizio VT420M LCD TV

It depends on what is causing the problem. How good of a deal are you getting?

Back-light problem. Check and replace damaged component/s at its back-light inverter board, or replace this board as card basis. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. It will be best to replace the inverter board as card basis.
http://electronicshelponline.blogspot.com/

I had a similar problem a while ago! I checked up some threads around the web and it was when i found out a tip about replacing the inverter board pannels of the backlight!! guess what ? It worked for me... My Vizio HDTV is about 5 years old so far and it is up and running like a champ...!! I hope it works for you!

this sounds like a main board failure but a defective power supply can mimic some symptoms of a bad main board. I would recommend you get a diagnosis done on the set. If I was a betting man, I'd guess the main board

I would suspect the main board as well

Send your email address to me by Fixya comment, and get a copy of the service manual by return mail.

If you have not been using the TV for quite sometime, moisture would have developed some defects inside the TV when you switched on. Sometimes even insects and lizards might get in and cause short circuits. Anyhow this might require attention by a qualified service technician.

Here is VT420M service manual.
Click it to download.
Thanks.

As of April 7, 2011 Vizparts.com has new shipment of main board #CBPF9D1KZ4 for $250.00 with a $50 core value, and 14 business days to return if not the problem. Also check Ebay search

The flickering is most likely due to a faulty fluorescent backlight. Once the bulb heats up the flickering usually goes away. Some bulbs are easier to replace than others so I would contact your local TV repair shop.