SUN Distributor Tester Balance Attempt With A XL335 Accelerometer

This is a first attempt to balance the rotating disk after removal of neon tube assembly and retrofit with LED. The XL335 ia a low cost $4 three axis accelerometer. It has a flat base which can easily be attached with double face tape. I filtered the output slightly with a .046uf capacitor to eliminate higher frequencies. Imbalance is most severe in the 2K to 2.5K RPM region. The LED is powered on all the time with a 15 ohm resistor. A once per revolution signal is created with a photo transistor. This should give an approximation of where the disk has too much weight causing an imbalance. This machine has a thin plastic disk for the light which has no weight. Earlier machines has a sizable glass lens. Be aware that the type of lens will change balancing. All weights in the form of washers should be removed first. Some machines may have an additional weight location besides the slide. I used to do a static balance by tipping the assembly on edge, spinning the disk and statistically seeing where the arrow ended up. Crude but it got me close. In any balancing the chuck needs to be closed and taped on the side to prevent it from becoming off center. Data suggests I need to add weight where the lens is. It seems counter intuitive. I really need to take the disk assembly off to verify what is happening before drilling random holes for weights. That is not on the schedule for now. Appreciate any ideas. Lots of these kits have been installed and there have been no questions about balance issues. These machines shake around enough when balanced. Issues don't arise till over 2,000 RPM.