Sony HP-810 stereo system has no sound coming out of the record player

[vortalexfan]

Hello, I was given a Sony HP-810 AM/FM Stereo Record player combo receiver from 1972 several years ago by my old landlord and I repaired it and sold it to a friend of mine to give to his son as a birthday gift but then his son moved into a small apartment that he didn't have any room for the stereo in so then I got it back because it actually was having trouble with the record player not working right.

So I got the mechanicals of the record player working but now the electronics aren't working right as there is no sound coming out of the tonearm when you try to play a record, which at first I thought it might of been a failing cartridge because before the audio completely died the audio was distorted and was only coming out of the left channel and the right channel was barely audible which is usually a sign of a dying cartridge.

I then bought a new cartridge an AudioTechnica AT3600T cartridge and hooked up the new cartridge and I still have no audio coming out of the unit.

Any ideas as to what might be causing the phono stage on this stereo to be dead?

Thanks for your help.