hifi engine

Teac A-2300SD Left Ch not recording, need help.

Refurbing this R2R deck, Ebay project. All mechanics now fixed. However, when recording, left channel signal is at input but not recording to tape. Left and right channel playback is fine using a pre recorded tape. Left and right erase are fine. Right channel input can be intermittant as well.

I'm about to thoroughly clean all tape/source switches etc.

Any help with typical things to look for would be much appreciated. Thanks..Jim