I was given a Sharp TV model LC-26SH12U which was purchased Nov 2007. When I turn on the TV there is sound but no picture. I am using the HMDI input from my cable provider. I do get a picture at times. It seems as if I turn off and on the tv eventually the picture will show up. I have worked tirelessly with the cable provider and it seems to be the tv as when there is no picture I also hook up another tv and get picture from the provider while I'm getting no picture from the LCD tv. Is there a problem with this tv?

SOURCE: Sharp Aquos LC-65D64U Picture Quality

You need to change your TV's settings and enhancements. Directly from the store and out of the box, the settings are adjusted for easiest sell in the store. That means that:
Your contrast is cranked to 100. Move this down to 50 to 60.
Your brightness may also be cranked up high. Lower it to a level nearer the middle range but not so dark as to lose detail in the shadows.
Your TV is set on "Dynamic" or "Vivid" mode. Pick "natural" or "normal" or standard.
Your sharpness is at least on, if not cranked up. Turn sharpness down or off, and the same with "Edge Enhancement" and "VSM", all to off.

Lastly, I bet you upgraded size and you are now sitting too close to the TV. Roughly, if you are sitting closer than 130 inches (about 11 foot) you might do some rearranging or save some money and get a smaller TV.

SOURCE: Sharp LCD LC-26SH12U

I see your post is about 6 months old, but I was having the same problem. After reading through forums for about an hour, I noticed that resolution was a common factor. I decided to take a shot and crank the res down to the lowest setting (800x600) using the 17" lcd that had already been working with the comp. I then unplugged the lcd and plugged in my tv and voila, I got a display. I then went into display properties and adjusted the res to the highest my tv would take (1280x768). You may just be trying to use a res. that your tv cannot accept. Hope this helps.

SOURCE: Sharp LC 46D85U TV with NO SOUND (but perfect picture)

Sound like the TV has a defective audio board. Opening up the TV would most likely void the warranty.
It's best to take the TV back and exchange it for a new one. Personally, I wouldn't want to be stuck with a defective TV ( that just came out of the box ) that they are going to repair for you.

SOURCE: The main fuse is blown. Replaced, it blew right

power supply unit has to be replaced.

SOURCE: sharp tv model lc-26sh12u very low vulumn

Yes, don't buy SHARP, problem solved! SHARP is the worst brand of LCD TV. I had to bring my brand new SHARP TV in for repair within 8 months of buying it brand new, and of course it was no longer under the 90 day labor warranty. Also, every person I know who has a SHARP TV has issues with volume and eventually end up with a black vertical line along the side of the screen within 1 to 2 years. I highly reccomend SONY, PANASONIC, even SAMSUNG, LG or VIZIO. Heck, I'd go with Toshiba or Phillips before I'd ever buy anything SHARP again I was so annoyed with their customer service.