Maintenance of Garrard turntables is generally quite easy, but the key word is routine. Of course, when you use a changer, one cannot really achieve audiophile grade results as one would expect from a 301 or 401 as there are so many moving mechanical parts. However, having made that honest statement, the truth is that you can achieve very listenable results. For Garrard connoisseurs who know their tables, the 40B shares many design elements with the SP25 MK3. To start with, with the platter turning (not while playing a record), rest your ear on the side of side of the top plate near the idler wheel area and listen carefully. You will have to diagnose what is contributing to the noise. In most Garrad changers that I have come across, the noisy elements are:
(1) the motor, either because the mounting rubber grommets have perished, or the motor lube has dried up. If this is the case, the rubber grommets will need to be replaced which is easily available. if the motor is noisy, it will have to be opened up, cleaned and lubed (especially the motor bearings and oil well)
(2) the idler rubber wheels in changers are under greater stress when compared to regular idler driver turntables. This is as the idler has the additional load of having to power the auto mechanism as well. Over years, the rubber hardens causing the idler wheel to become noisy when in contact with the platter's inner ring. If the idler rubber is brittle or powdery, its time to replace it. Also clean the inner rim of the platter
(3) older Garrard turntables were mounted on dampening springs. The transit screws should not be tightened. Tightening the transit screws results in a compressed spring mount and a noisier turntable
(4) the rest is all about lubing and greasing, when doing so always use a simple formula - if anything is rotating on a shaft, use lubricating machine oil, when 2 metal plates are moving over one another, use good quality silicon grease application, after properly clearing the dried-up grease. The platter bearings should always be kept well lubed.
(5) rumble can be reduced further if you mount the deck on a good plinth which is heavy and has vibration absorption characteristics. However, making these multi-layered plinths for record changers is not easy given the mechanicals under the top plate.
(6) if hearing thuds when the turntable is turned on and off, clean the switch contacts and check the existing spark capacitor. Add a capacitor it there isn't one in use.