I know this is kind of an older topic. But I wanted to add my 3 cents. I got the 830LE in June 2011 and am loving every minute I sew, quilt, embroider with it. I've put so many stitches on it I have had it in for servicing twice in the first year... like my car, I do my 'oil' changes on schedule and I"m a sewing addict. LOL. The 830 does require service after so many stitches.
I have had some tension issues the past few months too. But I"ve been branching out into different type and brands of thread. My goto thread for no hassles is isacord 60 and a titanium needle and bottom line. That is what I asked my service guy to set me up for. So all the default settings in the machine work perfectly with it. When I change to a diff weight thread or type (rayon or silk or cotton or different weight of poly) then I have to figure it all out again. I"ve been experimenting.
Just lately, I've also experienced some big snarls under the bobbin plate and that really is no fun. and starting out straight stiching also birdnests. My machine has never done this before. I'm using the thread and needle setup the technician recommends (isacord in the top and the recommended bobbin thread in the bottom). I think that the huge snarl that I had to cut out of my bobbin area shifted something inside the machine. The botton indicator is in the right spot. That snarl was so bad it pulled the fabric on my embroidery hoop down into the machine and ripped a hole in the fabric. This machine is very strong... I always use tweezers or a bamboo stick to push fabric in and for sure I always will (I don't want my finger to be sewn through the bone, and this machine could do it, i know it sews leather like a dream (i've done it)). Anyway after that big thread snarl, I can't get the tension right now. I'll have to pay for service this time though... My one year of free service has run out.
Unless anyone has some suggestions. It's mid november and I"ve got to get my christmas presents done. yikes!