I have a Viking and never have to adjust my tension. On the rare occassion that I have an issue with thread breaking I rethread it, if that doesn't work I try putting it on the table behind the machine or in a cup behind the table so that the thread comes off the top of the spool, or I change the needle, the wrong size needle will do that in a heart beat. Like to use serger thread and embroider FSL, I had to use double WSS and a size 90 sharp needle and slow down the machine. Normally when I try these different things one of them will work. I've had thread to do that when it worked the last time. I use all kinds of thread so sometimes you just have to give it the right conditions to work right. I think a big mistake is to immediately start messing with the tension. Also, make sure your pressure foot is up when threading the machine and the needle, having it down will really mess it up. Good luck. if you have to mess with the tension, all machines and conditions will be different depending on the situation so its hard to give a certain number to set it too. Make sure you write down what the orginal setting is before you start. Also, rethread the bobbin and make sure its clean