Maybe cartridge damage and/or the phono amp section of your amplifier blew something. Contact the manufacturer to see who can take a look at it locally.

I'm not familiar with the Dual 1264, but some automatic turntables I recall would mute their output when the tonearm was lifted. Is the 1264 automatic, that is, does the arm lift by itself when the record is over? And could you explain how you fixed it, is it working as it used to, or is the arm manual now? I'm thinking the muting circuit or relay may still be engaged.

What kind of sound comes out when you use the tape inputs? Is it just noise, or music but too quiet and tinny? If it's music from both speakers, the phono cartridge is probably okay, and it could be the phono stage in the receiver.

If you can borrow another turntable or receiver, or substitute yours in a friend's system, you could figure out which piece is bad.