@guidin they usually turn on then shut down again when they go into protection mode. This can be caused by shortened out speakers as well as hundred other things. It's time to take it apart and to have a good look at it. I would thing that with the age off it there may be a lot of degraded components etc. that could cause it. You can download the service manual for that [https://elektrotanya.com/pioneer_a-p510_p710_sm.pdf/download.html|from here]. Once you have it apart post some good pictures of what you find/see with your QUESTION. That way we can see what you see.