McIntosh MR78 tuner repair

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.

Ralph, thanks for your good recommendations. Actually just dusty on the inside of the glass. Not sure about the filter capacitors but I'll take a look while I'm in there. No noise while tuning but probably wouldn't hurt to Deoxit the bearings also while I'm in there.

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.

How I can tell the difference between an original filter cap and a replacement?
I've owned the unit some 6-7 years and don't know if the previous owner(s) had any service work done on it.

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.