As a fellow 704 owner, a bit of advice. Do not use the auto reverse if you can possibly help it. (You can disable it by programming auto repeat of side A.) The unit is like a Rube Goldberg invention on the inside, and the turn mechanism relies on a cheap little spring to get the laser pickup aligned when it turns upward to read side B. My player self destructed because of that cheap little spring wearing out!

You will also have to contend with slippage of the disc clamping mechanism as the rubber degrades over time, (the player might not be able to slow the disc spinning down when "stop" is pressed) but it's not as traumatic as hearing the awful sound of the laser pickup flying off it's little rails.

Did you solve your demodulator problem?