Some of these faults are specific to the Buswell Control panel -
As the stitch length is increased there will be a point at which the stitch starts to tear. This is because the rollers haven’t finished advancing the box before the stitching head comes down to make the next stitch. The maximum stitch spacing attainable with Lampomatics is about 100mm. If stitches smaller than this are tearing but stitches of about 15mm form OK then the head timing is probably wrong. The stitch head should stop with the plunger in the up position but before rather than after top dead centre. This gives the maximum advance time to the rollers.
Make sure when the head sensor triggers that the stitch head is clear of the box. This can be done by hand turning the machine with the panel power on – trigger the box sensor and crank the head round until the sensor lights. Check that the stitch head plunger is clear of the box. If not take the sensor drum off and reposition the arm . With Lampos it is easier to remove the drum assembly complete rather than trying to loosen the sensor arm -
Also check the condition of clutch brushes and that they are riding correctly on the slip rings.