Machine has locked up any suggestions on how problem could be repaired, nachine is model # 4618 LE

Instruction Manual Janome 4618 Digital Copy Janome Sewing Centre Everton...

Instruction Book 4618QC

JANOME NEW HOME 4618LE 4618QC Instruction or Service manual Parts on CD...

Not sure what issues you are experiencing.

Understanding Thread Tension Threads

Sewing Lesson 10 How to Fix Tension on Your Sewing Machine

How to Adjust Sewing Machine Tension on Craftsy

..

You might check out these sites for repair ideas:

Brother NS30 LE needle threader Google Search

otherwise you will need to contact Brother or a sewing repair supply for a replacement part

...

please use your search engine on your computer put in model + name+ number + manual + free

Just put it on STRAIGHT stitch and insert your needle flat side to the back and you're off!

It is probably one of two issues, the most likely being that the upper thread is not correct. Remove your spool of thread from the machine (also lets put in a new needle at this time) and raise the presser foot to its up position and rethread the machine and try again. If it works it was a threading problem. If you still have the same issue then you may have a damaged bobbin case. If the case is damaged it is probably best to let your local service store do it for you.
Good Luck!

http://janome.com/documents/File/ManualFile/4618LE_Instr_book.pdf

These machines are known to have this problem. The feed lift cam has a groove worn in it that won't allow the feed dogs to come back up. It is on the lower shaft and needs to be replaced. You can get the feed dogs back up by taking off the needle plate and lifting them up manually while turning the hand wheel. They should stay up until you drop them again.
Some people will not replace the cam and live with it.
good luck!

Do you know the looper threader broken can be repair by yourself? I suggest you to order the following product:
Sewing Machine Repair Guide
It's a professional repair guide written by an expert. Besides PfaFF sewing machine, you can learn how to repair other brands of sewing machine as well. The author claims that you can earn money after you had learned the repair skills!
Good luck.

Can you post a photo of this so we can ident the actual spring and etc, if it is the check spring, it certainly will affect thread tension.

Post to here or via
www.bargainbox.com.au and I'll see what we can do to help if it is not too late so many months after the original plea.