That Dual 500 is in fine shape. New Main Capacitors are a must. I have a new, proper (35,000uF 120VDC) pair for the Dual 500 if you want them. These:
https://www.tedss.com/2020064119?srsltid=AfmBOoptm86mdeTa7Op6EE-zkuEOB2XzM8wfCHON5G4k5jFwZt7mkII7
Send me a PM if you are interested.
Sincerely,
Mark