Speaking from experience, the largest concern will be the capacitors, both electrolytic and film. The electrolytic caps may have become electrically leaky as they lost their “form” while sitting. The paper film caps used at that time may have also become leaky, where there is zero tolerance for leakage. This can throw off the normal operation of the circuitry causing poor, or no, sound. When a long disused device like this came into my shop, I would test the caps, and if they weren’t too far gone, I would slowly bring up the mains voltage over time to allow the electrolytic capacitors to reform without drawing too much current and potentially exploding. My general opinion is, if you intend to use this machine for serious tape playback, get it into the shop for a recapping, and a mechanical cleaning and relubrication. The heads can also be checked, to be sure they aren’t too worn to reproduce your tapes well. Best of luck!