Stitch spacing too small
This is usually due to a lack of overexcitation drive. Check that the 40 volt fuse is OK. If the fuse is OK try removing the fuse and check that the red LED lights up, if not there is a fault in the power supply. If the fuse blows again when replaced there will be a fault on one of the driver boards. If the fuse only blows when the machine is operated look for short circuits around the clutch-
Unless a failure has been caused by a short circuit it is most likely that the top driver board (roller drive) is faulty. This is because this board is more stressed than the head driver. The most likely failure is an emitter to collector short-
Stitches get more spread out as the machine is operated and close up again after
a rest -
Erratic stitch spacings -
Machine puts second set of stitches in the middle of the box
This is caused by the box sensor re-
Disable the rising table trigger arm and see if the fault disappears. If so – check that the switch contact is fitted with a suppressor.
First stitch position sometimes too short
I came across this problem only recently and it turned out to be the box sensor was seeing the box about 6mm before the box was caught in the nip rollers. All was fine if the box was pushed into the machine smartly, but if there was some hesitation the first stitch was short. Make sure the box is in the rollers before the sensor makes.