Any repair guides for the Panasonic 1297 out a 91?

I am looking for a repair guide or any resources about the Panasonic 1297 internals. I have troubles with the cassette deck and I guess the amplifier since the sound seems pretty quiet.

Thanks in advance!

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Power is coming but sound is not coming

crwdns2934271:0crwdnd2934271:0crwdne2934271:0

Had you tried watching this?

Inspect for any cold solder joints

https://www.youtube.com/watch?v=l-dhs_9J...

https://www.youtube.com/watch?v=l-dhs_9J...

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