Try uplugging the power for a few minutes.
Although your problem regards how to turn off the SAP,
read on, what I found out this evening might affect you.
I have that same RCA model myself in which the audio went silent while watching it. Today I got around to taking a closer look at it. Hours of troubleshooting (& searching online) later and turns out all I needed to do was unplug it.
It seems that the SAP, CC, Auto Clock, Program Guides and other "eXtra Digital Services" in the originating digital XDS signal contain an extra 2 bits. This non-standard (and illegal)
signal reportedly causes a buffer overload in the microprocessor in your TV. Depending on what brand of TV depends on how those 2 extra bits manifest itself in the TV.
RCA mutes the audio....like mine did.
Sony drops the video, and Philips tint shift to full green,
Hitachis are affected somehow also.
The only way to "fix" these problems are to unplug the power
for a few minutes...and in other cases for a whole day.
You might pay attention to what channel you're tuned to if it happens again. I've seen a LOT of complaints tonight that mention weird stuff while tuned to the SPIKE channel.
Gotta love electronics
Good luck
MWallace, January 2006