Sudden Loss of Upper Tension - Kenmore 1940
 

I've been happily sewing tons of 1" squares together and this morning, just as I was joining the 12" blocks together I totally lost the upper tension resulting in large loops underneath. I've removed both bobbin and top thread, brushed for fluffs and re-threaded several times. The tension disks don't move as I increase the numbers on the tension dial.

Before I pack up the machine and head to my local repair shop, has anyone experienced this and found a solution?