My quartz locked direct drive PL630 no longer seems to quartz lock. It runs well and speed is stable without the quartz lock. When the quartz lock button is pressed the meter needle moves from the unlocked position indicating a speed increase of a few percent - and moves to this indication no matter as what speed the lock button was pressed. I have tried the normal switch cleaning procedure but it is still not working properly. I would appreciate any help with this - thanks
