Hey all, Sometime ago I was gifted a defunct grey-era 464 from my professor. After cleaning the solidified lubricant on the plastic gears the machine worked *near* perfectly. By that I mean, it passes sound, records to tape, and works as you'd expect a 4-track to work. My problem is, it seems there may be a problem with a motor or a belt because I'll get very intense pitch dive bombs, as if I abruptly sent the vari-speed from max speed to min. Normally, I'd say this is a fun and cool quirk to working with a cassette machine but it's proven to make overdubbing near impossible. Has anyone ever encountered a similar problem with their portastudio and has any advice for how to proceed? **PS the belts were all replaced prior to it being given to me and are seated (to my knowledge) correctly.