I am trying to rescue an old Panasonic VCR PV-7664. All functions work as intended except that the sound intermittently diminishes from time to time. It has very clean video playback, however the sound, intermittently goes near muting from time to time. I have tried with several tapes, cleaning the heads, video path, unglazed the pinch roller, adjusted the audio head bracket. No change. The problem persists. Also, the sound can be perfect, loud and clear for as long as
15 min before it looses the loudness again. The sound loss lasts for about a second or two. Than it returns to normal like never happened. I really appreciate if someone can share his wisdom on this issue. Thank you.