Who services older equipment?

I have some 70s era Marantz components I would like to have serviced. I purchased new the following: Model 140 power amp, 3200 preamp, and 112 tuner. The tuner looks great but needs adjustments. The preamp has one channel not working.
The amp works great and is used in my bedroom system. They all look very nice and have nostalgic value, so I would be willing to spend a reasonable amount to fix. Any help in servicing this gear would be most appreciative. Alas, these are all ss, not tubes!

Jim Robinson