Try Randal Young or acronym EZEKIEL in Audiogon. He specializes in vintage gear. He totally and entirely rebuilt a Harman Kardon 730 Twin Powered receiver I fetched from Ebay with all sort of SOTA newer parts, going step by step and charging more than affordable rates. Not many are as honest and as affordable, asides from being extremely competent as him.
My "new" receiver sound more like a 4K all in unit rather than a common, mid fi receiver that is 26 years old.