All thread breaks? Or just the spool you have on now? Also try running a couple lines of sewers aid down the spool/cone. It will work it's way down the thread path & help lubricate anything causing friction.

Is the machine on a quilting frame?

Floss the thread path with dental floss. That's a trick they use on embroidery machines. Watch the floss as you pull it through and see if it struggles to get through a particular spot or gets roughed up in a certain area.

I have had my needle just barely grazing the side of the hole in the single stitch plate causing it to fray so I had to move it over just a smidge. I have also had it rub on the foot causing fraying of the top thread & breaks.

Ditto!

Yes, it's all threads. What is sewers aid?
Thanks, I will try the dental floss. We found one place where there was a small burr. That's a great idea. I knew another actual sewer would have ideas.
Thanks again and have a great day. No sewing for me today, we're out of town to our great grandchild's first birthday party.
Can't wait to try all the things that have been suggested.
Immeme

What is sewing aid? I tried the dental floss and I didn't find anything. I changed the kind of thread and tried sewing slower. The thread still broke and had a frayed and tasseled look.
Does anyone else have any ideas? No matter how unlikely. That's where it's got to be.
Thanks
Immeme

Sewer's Aid is a liquid that re-hydrates dried out thread. It works wonders for me when machine quilting.

If you didn't find any rough areas with the dental floss, I'm thinking the thread is rubbing somewhere. Can you try running the machine on scraps but watch the thread instead of what you're sewing or have someone sew while you watch the thread. Track it all the way from the spool & watch for the fraying to start somewhere along the path.

I have had mine fray on the side of the hole on my straight stitch foot and plate. I had to move the needle just a smidge.

Take the stitch plate off and look on the bottom side of it to see if there is anything near the hole that could cause fraying.

With the stitch plate off, Needle down and see if there is anything touching the needle or thread on the way down to the bobbin. The needle should be a couple hairs away from the bobbin hook but not actually touching it.

You haven't dropped your bobbin or bobbin case recently?

Did you say this was on a quilting frame or not?

Yes, it is on a quilting frame. Tommy even put in a new bobbin case to see if mine was defective and it didn't change nything. He also watched it sewing very closely. I will do it again though. Can you get sewing aid at Hancock's or JoAnn's? I will definitely try some.
Thanks for all your suggestions. There's got to be something that will work.
Immeme

Is this in the tension dial? If it is, he took the whole dial piece out of the machine checked it and put it back.
Thanks

I believe I got it at Joann's. It's in the notions area.

Does your machine sew fine off the frame? I didn't realize it was on a frame or I would have started with that question.

Your shredding & fraying could be caused by the batting, too much tension on your sandwich or quilt is too high off the machine bed. Some fabric will also cause thread to shred and/or skip. The rubbery feeling white on white and the really tight batiks.

You didn't mention which needles your machine takes so I'm going to presume it takes regular domestic needles. I know some versions of the Janome 1600p take the round, industrial type so if your's is one of those, forget the next part. Use a top-stitch needle. It has a larger eye or the largest metallic needle you can find. If the thread appears to be fraying at the eye.

I just realized that if your Janome is one of the ones with the round shank needle, you could have it in backwards but I would think the technician checked that. The "scarf" faces front and some machines like the needle to be slightly off the 6 o'clock position--say 5:30 or 6:30 but no more than that.

I hope you are trying one thing at a time & testing. I've confused myself just typing this so that I have to keep re-reading what I typed--LOL!

Yes, I'm trying one thing at a time.
I know about the round needle. I've tried the ones that came with it and the ones I got from my tech.
I'm using the same batting I always used. I guess a batch could be faulty for my machine.
I don't think it's too high but I'll check it for sure.
I'm using muslin for testing right now.
Nothing really changed from when it worked and when it stopped that I can put a finger on.
I'll try these things and get back to you.
Thanks so much for your help.
Immeme