I think the VHS side of my VHS/DVD player is defective

I usually use it to play DVDs, but this weekend I decided to get out my old VHS tapes. I popped in a Wizard of Oz VHS tape from 1999 and the picture is fuzzy and grainy. I adjust the tracking, and the picture improved but the sound went away. I tried several other VHS tapes but they had the same problem. If I adjust the picture I lose sound, if I adjust the sound I lose picture quality. My guess is that my VCR is decoding audio at the wrong frequency.

You've tried cleaning the heads? Normally helps with grainy picture.

And be sure to inspect the tapes carefully before inserting them into the VCR, because old tapes can often get moldy.

Also, make sure the tape advancing mechanism is working properly. The capstans and the pinch rollers should be keeping the tape taut as it travels across the read heads.