Yes, SQUELCHER is a Scrabble word!

Letter values in Scrabble US: S 1, Q 10, U 1, E 1, L 1, C 3, H 4, E 1, R 1.

Is it a valid word?

SQUELCHER is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a crushing remark
an electric circuit that cuts off a receiver when the signal becomes weaker than the noise

Also: put-down, squelch circuit.