I have talked to several people with this problem. I just purchased a sony 350LX belt driven manual turntable, it worked fine for about 30 minutes, but now the rpm's slow down then speed up. It has a strobe, and you can tell by looking, even before a record is placed on the platter that the speed is slipping. There are adjustment screws on the bottom, which I understand will effect the resister speed, but no guidelines on how the adjustments should be applied. I understand that quite a few of the new turntables require these adjustments, however, I have found no tech support, including the folks at sony who seem to have the know how. Any guidelines on this issue would be appreciated.
Are you referring to the Sony PS-LX350 ? . If so ,have you moved the pitch slider up or down to fine tune the speed ? The Zero on the Slider scale is usually not accurate,tho you can set it right by using the two screws underneath.I don't recommend this as the two screws are actually very fragile electronic components on a small circuit board and requires a very small screwdriver and are difficult to locate using the holes provided. Also one small Quarter turn or so will throw the speed way off the slider scale.