Missing voltage? according to hitachi guide, y-sus board should have vsc,-vy and vsetup. I get -vy(75 dc) but vsc (12dc should be 200) and vsetup(40 dc should be 190dc). Can not adjust? All reading on the y-sus board

There should be a label on the inside of the cabinet saying what the voltages to the VS and VA should be along with any other voltages that are adjustable, have you set the various voltages to the correct specs

The main power supply regulator section circuit fault. 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. 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.
Search the site by type in the "brand name" to your device; in the "Search box at the top right of the display window of the Homepage" to get gathered related posts.

first thing you you need to do is open the back cover for trouble shooting. then check the normal connection of all the connectors and then look for the back light if their is a maldischarge from the module.disconnect all the connectors to isolate excessive voltage. turn on the tv and check the Y board if normal the Va, Vs, -Vy and Vsc voltage are all present.the same thing with the Z board the Vzb, Vs and Va voltage if normal,check if no blown fuse.there are FET at control board check the 3.3v, 1.8v and 5v.be careful always especially in performing voltage checking.

check your sdr boards. you can test them with a multi meter. they are known for going bad. what happens is the two caps by the output go bad on the power supply and they make the sdr boards burn out. you can replace the two caps and save lots of money. then please check out this web page http://www.hometheatershack.com/forums/hitachi/38229-hitachi-p50h401-led-flashes-3-times.html

This web page has info about repairing these. The 4 flashing lights maybe the x sus or the y sus but it's still a good idea to check the sdr boards since its a common failer. I had one tv with a bad sdr board flash 3 time and another set it was flashing 4 times.

Usually it is the Y-sus that has the problem. This is one of the boards that sustain the picture on the screen.

For this particular issue, there could also be issues with the y-drives and Z-sus. The way to find out for sure is to take the voltages (Va, Vs, Vcc, etc) on the boards and matching them up with the specified values on the panel.

Try to adjust the Vs voltage on the power supply by lower it a little bit or increase it a little bit. It will help to decrease the red pixel flashing.

Measure the -Vy and Vsc on the Y Sus board. If there are no voltage reading then you have to replace both of them.

Hope this will help!

Dave you are ****** you never help

send an email with the schematic and I'll try to point you in the right direction.