How many fuses in a 50hp66

Contact the authorized service centre for Toshiba. Fault with the main power supply regulator 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.

sent me a copy of the schematic

if you don't have a picture but don't have sound, that could be a backlight problem. Take a bright flashlight, turn on the set and shine the light on the panel. If you see a faint image, you have a back light problem. If you don't see a faint image, then I suspect a bad scaler or t-con.

ISSUES:

1. IF sound main fuse/s are good.
2. If no power or standby check main fuse, standby power supply and any signsof damage you can see---burnt parts etc.
3. almost all these sets the troubleshooting involves checking voltages on the main power board to narrow down theproblem.
4. Be safe and if you do not know what you are doing don't open the set.

Answers to issues:

1. RE:fuses---if a blown fuse is found get a good replacement(not the genericones like Radio Shack). Many fuses are special even aside from amperage--Don'tput a higher rated amperage fuse in the set for any reason.

2. RE: power supply in set: if total dead aside from main fuse the set uses astandby power supply that runs 7/24 and a main supply (some are combined andsome not.

Here aside from checking fuses you want to examine all the filter caps on thepower/standby to see if any are puffed up or buldged up in some fashion--Iattach a photo of a good one---top should be silver metal and PERFECTLY flatand have no brown material coming out on top or bottom.

What happens in the standby area is they use caps with too low a voltage rating(saves money) which causes them to fail in a year or two---the standby runs7/24 and the heat dries out the caps and they fail.

3. Trouble shooting consists of the above and then at some point you have to buyand try a board to see if it fixes it or not.

4. Safety first--no TV set is worth getting injured or even killed over.If set is opened at least look for puffed up and bad caps like in thisphoto.

I see so many here with no sound/nopicture issues:

ISSUES:

1. IF sound main fuse/s are good.
2. If no power or standby check main fuse, standby power supply and any signsof damage you can see---burnt parts etc.
3. almost all these sets the troubleshooting involves checking voltages on the main power board to narrow down theproblem.
4. Be safe and if you do not know what you are doing don't open the set.

Answers to issues:

1. RE:fuses---if a blown fuse is found get a good replacement(not the genericones like Radio Shack). Many fuses are special even aside from amperage--Don'tput a higher rated amperage fuse in the set for any reason.

2. RE: power supply in set: if total dead aside from main fuse the set uses astandby power supply that runs 7/24 and a main supply (some are combined andsome not.

Here aside from checking fuses you want to examine all the filter caps on thepower/standby to see if any are puffed up or buldged up in some fashion--Iattach a photo of a good one---top should be silver metal and PERFECTLY flatand have no brown material coming out on top or bottom.

What happens in the standby area is they use caps with too low a voltage rating(saves money) which causes them to fail in a year or two---the standby runs7/24 and the heat dries out the caps and they fail.

3. Trouble shooting consists of the above and then at some point you have to buyand try a board to see if it fixes it or not.

4. Safety first--no TV set is worth getting injured or even killed over.If set is opened at least look for puffed up and bad caps like in thisphoto.

Generally this problem is in your signal board. You may also know it as the scaler board, as you mentioned. I have not repaired this particular model. But I would first suspect the the signal board (scaler). If you are not sure what this is, it is the board with all the RCA Jacks and RF connections. The problem in this area are bad or failing capacitors. Thanks for asking and show all hands of support!

Change the Scaler PCB CEF156A

This set is a 50" plasma. first check the AC power fuse on the filter board then: if it is bad: check the power supply by marking and, removing all the cables; (so you can put them back in the correct spot) except the filter board to power supply cable; that connects to the Power supply board. Then: replace the blown AC fuse and, re-power: If the power supply blows the fuse: again, the power supply is bad and, must be replaced or, repaired. If the fuse does not blow: turn off the set then: on again, reconnecting and, disconnecting each board cable in turn, untill the fuse blows again this cable leads to the bad board; replace or, repair the board that blows the AC fuse every time the bad board is connected, irregardless of which other cable to the power supply may be connected also; or, not.

I bought a Scaler board from someone on eBay but it did not fix the unit however I'm not sure the replacement was not a dud. I planned to send the board to PTS Corp but haven't yet. I have sent other boards to PTS wit good success. http://www.ptscorp.com/tech_support.html

the fact that you have on screen display tells me that you are on a blank digital channel, or input with no signal. check to see if this is so on all of your inputs DVD, VCR, Cable, Sat box... if there is no signal still, replace the scaler board.
here's the four basic components to a LCD tv.
1. panel. there is on board electronic inside not componet level repaired.
2. power supply. this feeds power to the unit 5V, 24V, and 15V. the 5V is the standby voltage while the 24V supply the inverters.
3. the inverters. this is a DC to DC inverer used to light the lamp. these and not component level repaired.
4. the scaler board. this is the board that runs the show. it sends the signal to the panel to paint the picture.also sends commands to the power supply to turn on the inverters. this board is definatly not component level repaired. most all of the boards can not be repaired at the component level, power supply may be the only one, but not all power supplies can be.
there is one other part to the set that does have failures and that is the cable connecting the panel to the scaler. this is the LVDS cable. sometimes just reseting the cable can solve many problems.
so based on this info your panel is working because you have onscreen display. your iverters are working because without the lamps you would not see the on screen. your power supply is working because you have inverters working. and the only thing left is the scaler this provides the on screen so we know that it is at least partly working.