u/Intrepid-Onion-9695

I picked up a JTM60 out of curiosity and because I got it really cheap (160 CHF). Cosmetically it’s in pretty rough shape, but it works perfectly. The sound honestly blew me away. I figured it must be some kind of budget Marshall because of the price, so I’m wondering—what’s the catch?
I’ve heard people talk about heat issues, but I guess if this one has survived 30 years already, it’s probably not too bad.
If I take it in for a service, what parts would you recommend replacing as preventative maintenance while it’s on the bench?