How to switch to antenna usage without a remote for a sharp model 27K S100

Set-up procedure is too much to type in here, and is not practical and it will differ brand-to-brand remote controls. If you wish to get more; check the site linked here. It has set-up code list & set-up procedure to many popular brand remote controls. See it in "Mosaic" or "Magazine" view. It will make surf easier.
http://electrohelponline.blogspot.com/

Its likely Mute or a lockout on the audio, if out see if you have the owner manual and or the remote that came with the set, the item seen on screen is a clue.

Only with the original remote.

0093, 0039, 0165, 0157 one of these should work

You don't. A good "universal remote" available from Radio Shack (Phillips) for about $15 will provide access to all TV adjustments. Easy to program for all TV models, VCR's, DVD players, etc. About $35 + S&H for the Sharp remote replacement.

Possibly the main Power Regulator is damaged!!!

Open the case, then look for anything that burned out, replace it!!!

If still won't start, you need a multimeter, soldering iron, try locate output diode on power regulator board, then measure the voltages, it has 3-4 type of voltages;
first diode it should around 115V-130 V DC.
Second diode it should around 24 V DC.
Third diode it should around 11-16 V DC.
Fourth ( if exist), check diode and should around 5 V DC.

The problems usually start on second diode, if persist, follow the circuit board.

go to www.comcast.net and click on the Help link, you should be able to find the remote codes and instructions on how to program it...also do a google search for COMCAST REMOTE CODES.

You have done everything that a consumer can do. The problem is most likly in the horizontal section of the tv. This will be something for a repair shop to fix.

The bad thing is that not all universal remotes work for all functions of a tv. The thing is the factory remote. Order one at ROMOTES.COM. They sell them at a good price.

Can you use the remote control to change the channels? If not, it may be that to need to reprogram the remote to work with your TV. I just had the same problem. I have GE universal remote and have reprogrammed it to work with my SHARP 27k-s100 TV by following these instructions: http://www.ehow.com/how_9190_program-ge-universal.html The code that worked for my TV is 173. Other codes listed for SHARP are: 004, 006, 012, 029, 095, 111, 112, 113, 122, 171. Good luck!