not to contradict vicki's advice. just something to try as a "what the heck".
my favorite machine started having tension tantrums recently. it was driving me right up the wall. it just so happens i recently decided to splurge on some 100% cotton thread because i wanted to see what all the excitement was about. until now, thread was thread was thread ... y'know?
well, much to my surprise, i not only found some 100% cotton 50 wt/3 ply for less than i'd pay for a blend at walmart, when i put a bobbin of the stuff into my machine, the tension was suddenly perfect!!!!!
i don't know if it's the difference in weight or content, but i soooooooo don't care. it solved my problem AND will save me money. (i can still use the thinner poly/cotton blend in the top. thank goodness. i have a lot of it to use up. the thought of tossing it or letting it rot from old age was killing me. LOL)
here's what i got
http://threadart.com/shop/category.asp?catid=5
i know many people swear by the more famous and exponentially more expensive brands. to each her own. but this works for me and my budget. :P