What are the symptoms of a Vizio e601i-A3 main board that has gone bad?

bad power board

Vizio had a recall on this model TV resulting from the issue your having, below is a link to the recall. What they said was recently Vizio put up a special bulletin on its website stating a number of its 60-inch E601i-A3 and 70-inch E701i-A3 HDTVs may lose the picture (but maintain audio) due to a bad "chip assembly". The "chip assembly" is actually in the main board, Ive fixed a number of this model TV's by replacing the main however Ive also seen the lamps fail as well so its kind of a guessing game as far as where the issue is at unless you have some high end test gear to troubleshoot the set.
Vizio Issues Recall On Large Screen LED LCD HDTVs

You have a bad tcon board or the panel is bad but this set has some issues with the tcon board...you could try baking it if you wanted, its not going to hurt anything

Can be the TCON board or the Main board. Can confirm by replacing the TCON board.
If you wish to get some details; visit the site linked here. Pull up older posts. http://electro-medical.blogspot.com/

Does appear to be a PS issue.

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/ To some model sets; especially LED back-lighted types; the back-light inverter circuit will be part of the main power supply board [SMPS]. In such cases, the power supply board might need replacement. To some models sets, the back-light inverter and SMPS section circuit will be integrated at its main board itself. If so; the main board should be replaced. To some models of sets, all these section circuit will be integrated at its main board. If this is the case, you have to replace the main board.

To get help need to know exactly what the symptoms are so that wrong boards do not get replaced. Now doesn't that make sense?

Fault at its main digital board. Short circuited component/s at it. Contact any service technician; or the authorized service center. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts.
http://electronicshelponline.blogspot.com/
In most cases, the main board might have to be replaced. If so, a software [firmware] update too might be necessary.
Before going further; try a hard reset first. If it does not help you, replace the main digital board. There are two methods to reset TVs. The first is simple to do; a Hard Reset. The other is somewhat skilled; is a Factory Reset (System Reset). To make it a hard reset, just unplug the TV from AC mains wall socket, and re-plug it back after 15 minutes or so. If you do this by overnight is better. This procedure will make it a hard reset. If you want to make it a system reset [Factory Reset]; you have to enter its service mode option, and select the factory reset option. If you wish to get some details; visit the site linked here.

Fault at its main digital board. Short circuited component/s at it. Contact any service technician; or the authorized service center. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts.
http://electro-medical.blogspot.com/
http://electronicshelponline.blogspot.com/
In most cases, the main board might have to be replaced. If so, a software [firmware] update too might be necessary.

Fault to the main power supply regulator section. Either it will be a separate board, or the part of main board. Check and replace damaged component/s at its main power regulator [SMPS] section circuit. Contact any service technician. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts.
http://electronicshelponline.blogspot.com/
It will be best to replace the power supply regulator board as card basis rather than making "Surgery" to it; which usually will make loss for both money and time. Even though you can make it right, it will cost around an amount equal to the cost of a new board; including the cost of (spare parts + service charge) More to say, most of the spare parts to it will be difficult to get from open electronic spare part market. This is true to most of the flat panel TV power supply boards; irrespective of its brand and screen size.