What's wrong with the phono section? Have you tried putting a low level input to the Mic input? Both usually share the same amp.
If both are completely dead, some body probably over drove it with high level input.
Try cleaning the RCA jacks, low level inputs can be greatly affected by dirty contacts. I'd also clean the fuction switch and tape loop switch at least. Amazing what cleaning controls can do for these old units.
Good news is phono amps are simple and parts are cheap, so it should be to expensive of a fix.
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