Marantz 5020 Cassette deck - left channel problem

[myopia]

Hey there, new to AK.
I picked up a Marantz 5020 Cassette deck for a few dollars at a sale. Got it home and cleaned it up, it's cosmetically very nice. Mechanicals are good, rollers, belts, speed... all good. Inside looks very clean and nice as well.

When I first plugged it in I got sound from left and right, but there was hum. Left VU didn't move, but I thought it would just be a broken meter.
I assumed I needed to hook up a wire from the chassis ground on the back of the deck to my ground on the amp. Did this, listened again and the left side has noise and static with a faint hint of music in the background. Left VU doesn't move. Changed RCAs and removed ground, sounds the same. Tried my 2nd tape inputs on the amp, same. Cleaned the RCA jacks on the back of the deck. Other sources sound good through the amp so speakers and amp are OK. Tried multiple tapes. Sound through the right is great!

Any owners of this deck had the same issue before? If anyone has a PDF service manual or schematics would be most grateful...

Thanks

http://www.jamesvanarsdale.com/myspace/marantz5020.jpg