The AVR's SAT/TV input works fine, but when I use the MD/DAT input for watching the TV or VCR, the sound only comes out of the left-front speaker. When I record something via the VCR's line in, the playback has the same audio problem. But when I play a tape recorded over a year ago, the sound does not have the audio problem.
Clearly, something failed a few weeks ago. It's not the AVR's MD/DAT input, since the problem does not occur when you play older tapes. The first thing I would do is connect the VCR's video and audio output to an analog input on the AVR and see if the problem persists. If it does, the fault is in the VCR; if it doesn't, the fault is in the TV. Another test would be to play a recently recorded tape on another VCRperhaps in a completely different systemto see if the right-channel audio was actually recorded or not.
I suspect that the VCR's right-channel audio circuitry has failed at some point other than the playback-head output. The right-channel audio from the tuner and line input doesn't get to the record head and/or the final output, but it does get from the playback head to the final output. In this case, I doubt it's worthwhile to repair the VCR; your best bet is probably replacing it with another VCR or, if your main application is recording TV shows for time shifting, a DVR. In fact, if your Dish receiver isn't a DVR, I'd upgrade it and lose the VCR entirely.
If you have an A/V question, please send it to firstname.lastname@example.org.