There has been frequent postings on various repairs for broken 577 CTs. However, mine is working ok, given its age and typical senior citizen arthritis issues.
I don’t want to fix what ain’t broken, but it would be nice to have a list of:
1) must do - or it will explode
2) should do
3) when you have the time do
My 577 issues are buttons that don’t want to latch, pots that are scratchy, display zero moving around with selector setting changes. All things that I can live with.