on a long- or mid-arm, you have to adjust the tension for different threads. At least on my HQ16, a small turn on the upper thread just won't cut it. Think in terms of half-hour or three-quarters of an hour for each upper adjustment. However, you should adjust the bobbin first. Look for you-tube videos for your set-up, see if the mfr. has on-line videos. After the bobbin tension is correct, then turn to the upper thread to adjust. It takes time and practice (ask me how I know! LOL). Stick with it, it sure is worth it.
Laurie