I have an Hitachi LE55W806. The hdmi inputs quit working, the AV and component inputs work fine. I've been told to replace the main board, but can I repair it instead?

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. To some model sets; especially LED back-lighted types; the back-light inverter circuit will be part of the main power supply board . 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.
http://electro-medical.blogspot.com/

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.

Is it set to handle HDMI?

how do you set up the HDMI input on a hitachi tv model #51F59A ...

https://answers.yahoo.com/question/index?qid...

Jan 8, 2010 - i tried to hook up an HDMI devise but i cant set it on input HDMI it ... My TV has HDMI, Component and AV inputs, which one should i use for my ...

HDMI not working - Hitachi 50VS69A - AVS Forum ' Home Theater ...

www.avsforum.com/.../948284-hdmi-not-working-hitachi-50vs69a.html

Dec 1, 2007 - 7 posts - ‎2 authors
I have a Hitachi 50VS69A 50 RP LCD HDTV connected to a Dish Network receiver that the HDMI input is not working on. I have been using the ... Hitachi P50H401 - all HDMI ports are dead - HELP!
6 posts
Oct 2, 2008
Hitachi 51/57/65F59A CRT RPTV Tweaks Thread
30 posts
Jan 19, 2007
More results from www.avsforum.com

Depending on the TV model, there were some where the IR (Infrared) board inside the TV failed. It is not the remote that failed. You can test the remote by trying it at a Best Buy store on some of their TV's. If you are somewhat handy, you can easily remove the IR board and send it into a repair service that I located on E-Bay. There was repair service in Indiana and one in California. I sent it to the California and it came back in less than 1 week. I installed it and the TV works fine now.

I may put money that some one did stole your internal cable from the power supply to the main board !

Don't be surprised they did it to me at LG company .

All inputs are processed through the main board, I'd replace that

If you still have audio and video from component and RGB which means your sustainer boards (the boards on the two sides that powers up your screen) are working. All you have to do is replace the main board. you can buy parts at Vizparts.com, Vancebaldwin.com or shopjimmy.com. Make sure that you give them the correct model and serial number so they can send you the correct part.

Component ports can and do fail. You can get a replacement board from here: TV Parts Universal TV Stands DLP Chips ShopJimmy

You may have to activate that imput through your menu.Alot of plasmas have the ability to mute imputs.