Nakamichi receiver RE-10, microprocessor problem?

[box63]

I have a Nakamichi stereo receiver , model RE-10.

Problems include:

-mute button doesn't work. Press mute and for a fraction of a second it mutes but then un-mutes immediately, then won't mute at all.

- speakers cut in and out with volume raised up to approx. 40%

- external audio inputs don't feed the audio signal through the receiver properly. If an audio source is input into the "CD" jacks, then I have to press "tape monitor to hear it. If I press tuner, I can hear both the tuner sound and the exernal source. If I connect the source to "AUX", then I have to press the "CD" button for the sound to come through.

I have replaced the analog source switching IC, LC7821 with no improvement.

Seems like it could be a microprocessor problem but I don't have a
service manual to help.

Where in canada would I get parts and service manuals?

Thanks for any help.