I have a Samsung LCD TV - model LN-3251D. My local cable company offers HD channels over the air; however, I canot seem to get them. How do I receive these channles?

The LCD screen panel is broken or damage.Not worth fixing,sorry.The LCD screen panel are 90% of the tv.The screen panel,will cost the same as a new tv,to replaced.The tv now,only can be worth as salvage electronic boards for parts.

Change the input to antenna.
If it says cable:
On your Samsung remote is a button that says antenna. You want it to say AIR. Air is an ATSC tuuner that allows you to receive over the air HD with a pair of rabbit ears.
If it says AIR:
If it says AIR and you still can't get the HD channels. In the menu it will say Channel. In that sub menu it will say autoprogram. Make sure you have an antenna connecte to AIR in the back of the set and autoprogram AIR only.

Any questions respond to this post and I will respond.

Have you check with the cable company to make sure they are broadcasting to you in HD ?
It takes more bandwith so some cable companies will charge extra for it so you will have to check.

I assume you have cable. The cable HD and digital channels are usually sent in Quadrature Amplitude Modulation (QAM). The cable companies are required to send local channels in the clear but not so for any others. Regular (basic) channels may be clear or scrambled. USA many not be but HBO will be.
So you have 1 of 2 problems: (1) your TV does not do QAM or (2) they have scrambled the channels you want to see. Questions: (1) Have tried direct Over-the-Air (OTA, ATSC) reception for your locals? (2) Can you see the HD local channels on cable? (3) Are you paying for an HD box from the cable company to have the channels decoded? If in doubt contact the cable company.
Current Samsung TVs do do QAM and OTA HD. Alternatives are Dish or Direct to get satellite with an HD receiver using HDMI or 5-cable RCA. Costs are comparable but OTA wins, hands down. -Ken

You have a bad Main bd. Have a trained Samsung tech repair the tv.

More often than not the problem is with the Cable co. They ALWAYS blame the tv. I have had many many problems with the signal quality coming from that co. Here is the most likley cause. The cable signal is probably very Weak. This can be caused by a weak signal coming from the cabls co. or a bad cable inside your home. The age of the cable can effect the signal quality.Note: The cable co is only required to provide a Digital signal. Some companies allow free HD signals and some charge for that signal. The correct approach to this issue is to get with the Cox and ask the if they provide free Hd channels without a box. If they say no then you will have to get a HD cable box to watch HD programs. Themn if they say yes then you need to ask them to send out a tech and test the signal coming from the Head End all the way to your set. If the signal flucuates then you will get inconsistant scanning results.

I lived with it for about six weeks, then took the back off the TV. Just now it seems to be fixed, but I don't know if it will last.

I disconnected the wire leading to the channel up/down, volume up/down and source board, turned on the tv, turned it back off, reconnected the cable, and everything seems fine now.

if you have a cable box then it is probably the resolution settings in the cable box, what type of cable box do you have

This must be the setup for your TV box. Contact the support for your TV box.

Normaly, the TV should auto select the proper operation mode.

Jerry G.

This set has a factory upgrade for HDMI problems like yours and it also fixes another problem for intermitent sound in the HDMI mode. This model is still under warranty. Call: 1-800-SAMSUNG To find a local servicer in your area.