[poppafred]

On the 97 with low audio - Punch the WX button to go to weather mode. Can you hear the NOAA stations? Have you tried an external speaker yet? Or earphones? That might rule out the speaker itself. Try jacking and unjacking the speaker a couple of times in case you have pocket lint or something in the headphone contacts. Trust me, that does happen.

Have you by chance programmed in a digital audio channel? If so, the digital audio channel will stop the scan but there will not be any audio. That's one of the reasons why the police are going digital, so crooks cannot listen. Also, sometimes, it is more reliable than analog. Plus, the manufacturers like digital and are no longer pushing the analog. It is cheaper.

On the nonstop 97 - try turning the squelch all the way open so you hear static, that would be full counter-clockwise. Will it stop on a channel then?

If the answers are "No", you better plan on trying to find a replacement scanner. It might cost more to repair than to replace. Keep asking around, maybe someone else has a better idea.