Tascam MSR-16 won't record or playback

[A Reel Person]

...

The head has to be spotlessly clean, like a mirror. The worst of sticky residue can be a black mark that looks permanent, but it's not. Clean heads should be shiny metal-looking.

A stubborn deposit of oxide can totally interrupt the recording process, but a prerecorded tape may play back fine.

 

[jameskimpton]

My recently gifted MSR-16 was exhibiting similar problems - Metering input but replaying almost nothing. Cleaned the heads, recorded....same result.
Grabbed my desk lamp to inspect the tape path - the guides, bias head and r/p head were clogged with black oxide.
After a thorough cleaning, sometimes getting my fingernail behind the cloth for the guides - the path was clean.
Rolled up a reel - Recorded and then replayed.
A lesson to myself to always, every reel, clean and inspect the heads - especially with 10 year old tape stock.
Phew - No trip to the broadcast workshop for costly inspection!!!