Hello, I hope it's not too late ...
I would suggest changing all the electrolytic caps .
Clean any dirt/dust out.
deox all switches and pots.
replace the two counter belts, they are probably in bad shape, you also may hear a squeal from the counter, I used a toothpick and some lubricant to correct that..
Check the condition of the two roller guides, they might need to be replaced. The DIY kit here is a good start.
Buy/download the service manual.