I've recently won a Philips D6645 "Skyrunner" on ebay. The unit is in good physical condition but when playing the tape is being dragged of at an angle thus losing azimuth alignment and also damaging the tape by creasing it. The pinch roller doesn't appear to have any flat spot and is completely clean. I suspect the pinch roller but is there anything else that I should look at? The drive belt has stretched but I'm not convinced that this would cause the problem unless you know something different! This seems to happen in the "A" direction.
