A KNOCK FROM MACHINE - Sewing Machines

Hm, could be several things. If stitches are not being formed, it could be a timing issue (the needle does not arrive at the bobbin at the correct time). Did the machine recently hit a pin or something hard? That will knock a machine out of time. There could also be a broken piece stuck that is preventing the feed dogs from operating. Thoroughly clean the machine around the bobbin area and feed dogs.

...

You know how to use a computer, get the make, model and serial numbers off the machine and search online for a manual. See what pops up if the manufacturer can't help.

Sounds like a thread jam ! Open bobbin case housing remove bobbin and clean away thread ! Do not force the balance wheel to turn or you will knock out the timing !

Depends on which belt. Your machine has 2. Better to take it in and have them replaced because it's VERY easy to knock your machine out of time. Have them clean and adjust it while you are there.

Take it in, the belt is inside along with elelctronic components that are seriously deadly to those inexperienced with electronics. Also machines with inside belts are very easy to knock out of timing.

So spend the $$ and have it replaced and the machine serviced and adjusted while you are there.

try youtube for a video

I guessing that from what you say broken both needles you are talking about a serger, unless you are using twin needles in a sewing machine
if the power has gone off, have you tried turning off the machine & turning it back on, if that doesn't work then it's possible that the power cord may have gone out, or the on & off switch may have gone out.
the only things broken needles will do is knock the machine out of time or jam it up

Do you have the right needle in your machine? There are some Sergers that take shorter needles and I have has some customers put those short needles on thier sewing machine. If the needle is too short it cannot pick up the bottom thread.

If that isn't the problem I would also try to rethread the machine and the bobbin. It sounds very simple, but sometimes you can miss a step

If none of the above don't work, you may have a timing issue. Have you run over a pin? or had the needle come down on a presser foot? Sometimes these sudden stops can knock the machine out of time.

You need to find out exactly where the noise is coming from, any unusual noise could be expensive in the long run.

I had that problem last year. The repairman told me to make sure my sewing machine was on a very stable table, or it would move around & knock out the computer. The machine just barely moved, but that was too much. After I changed the table out that the machine sat on, it worked. Hope this helps.