I'm fixing up a Grunow 570 cathedral with a slipping mechanical dial drive. It is the type with 3 large ball bearings enclosed within a pair of collars, and I see no obvious way to tighten it. I know Heathkit used a drive like that on some products - seems like there was no fix if it started slipping. Thanks for help.

If this is at all like the ball bearing unit used on the Philco 60, take the entire tuning condenser out of the radio. Disassemble the bearing-vernier unit. Wash the condenser and all vernier parts in mineral spirits. Then wash in soap and water to remove the mineral spirits. COVER YOUR DRAIN SO THAT THE BEARINGS DON"T GO DOWN IT!!! Grease the vernier assembly well with di-electric grease (found at your automotive parts store). Grease the condenser bearing and the end of shaft thrust surface. Place a drop or two of oil on any brass contact springs that make contact with the rotor shaft. Re-assemble the vernier assembly. Test operation. If you need to tighten up the vernier bearings, the outer shell that fits over the vernier bearings may have bendable tension ears where the screws go through. Bend these to increase tension on the cover. DO NOT DO THIS UNTIL AFTER YOU HAVE CLEANED THE CONDENSER AND ITS ASSOCIATED PARTS!!! Do not compensate for dirt and lack of lubrication!

Thomas