Adcom 535L upgrades?

Yeah, thanks @oldhvymec 
Appreciate it. I have a buddy who loves audio but can't really afford to do much right now. He's turning 50 this year and likes my Adcom. Either he or my son will get a present from me, and if it's possible to polish a radish for not that much money, it'd probably make a nice gift. My buddy has very decent Paradigm bookshelves and some Schiit gear, including a decent preamp. If it doesn't break the bank for me, seems like a no-brainer.

Have you looked inside the amp? Leaking capacitors etc..? Might just need a good cleaning the 535 while the lowest watt was considered one of the best performance for the money at the time.

https://www.stereophile.com/solidpoweramps/adcom_gfa-535_power_amplifier/index.html

I have looked inside. Looks fine. Works fine. I'm in the Tweak-light Zone on this one, for sure!

The 535i is a well designed amplifier and responds well to upgrades. Do a search and you'll find a good bit of information about upgrade paths. If I remember correctly it was a Nelson Pass design. 
Here's one:
https://hoppesbrain.com/2015/06/12/the-super-high-current-adcom-gfa-535-ii/
There was an outfit that specialized in upgrading 535i but I'm not sure if there are sill in business. Worth checking.  

I’ve owned a few 535s and they always worked flawlessly and sounded fine. I currently use a later 5300 as a backup/satellite (outdoor speakers) amp and sold the last of my 535s a few years ago. The 5300 is 85wpc and in my humble (!) opinion it sounds far better than a 535, even the later models (5 way binding posts added instead of the twisty things they had originally). I may get the 5300 upgraded someday or fixed if the caps get leaky as it just works as it should. Great torroidal/mosfet amps costing very little relative to how they sound.