McIntosh MR78 tuner repair

Cleaned? I assume more than just dusting it out?

How old is the unit? If from the 1960s, have the filter capacitors in the power supply been replaced recently? If not they are overdue.

If you encounter noise while tuning the station, the bearings in the tuning capacitors are corroded. They can be sorted out with a contact cleaner like Deoxit- spray into the bearings of the tuning caps and run the cap back and forth a few times.

Be careful if you decide to remove the glass- the lettering on the dial can be fragile.

If this really is an older unit get the filter caps replaced! Otherwise your power transformer is at risk and they are not easy to find.

Replacements will likely have a sticker identifying its brand, pin out and associated values. The originals will have that info stamped into the side of the part.