Victoria 537 Manual [extra Quality] -

Incorrect upper threading is the most common cause of loops, bunches, and broken threads. Follow these steps carefully:

Some Victoria 537 versions have a socketed EPROM (chip with a quartz window). Over decades, UV light and bit rot can corrupt data. If you have a programmer, read and re-burn the firmware from a known-good copy (available on vintage controller forums). victoria 537 manual

Dial controls for stitch length and width, as well as thread tension. Incorrect upper threading is the most common cause

Plug the foot control and power cord into the machine's terminal. Plug in: Connect the lead to the electrical wall supply. victoria 537 manual