MY RCA LED40HG45RQ - the sound has quit working. Picture is beautiful, but no sound. Is there a sound card that needs to be replaced or what would be a reset to correct this problem>

what red light.. the red light is useally stansby mode, and should turn of when tv is turned on.. maybe try new batteries

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. .

This probably will not work. The rca jacks are for a RGB monitor.

If you want to use a monitor, you can. Get a proper VGA cable and remember the drivers will need to ge updated, probably.

A shorted horizontal output transistor or shorted flyback. If the flyback is shorted replace also its HOT.

Use Extneral Audio Jacks to a stereo for sound or replace audio output ic.

check color code cables be sure all cable match up with the right inputs red to red and white to white rca or HDMI will same you alot of problems but sure that your tv have HDMI outputs

i have a 52 inch rca ,picture but no sound

Sounds like power supply. Probably time for a new tv. You have already got almost 20 years service.

your SSB board is the problem its either your audio output ic or the board its self use external jacks red& white use your stereo for sound. cost of SSB board is 292.00

you may coldsolder the tuner first before replacing the new one,maybe it can works.