I have a dressmaker sewing machine model number S-3000A serial number 8651 and I need a bobbin case and tension spring. My sewing machine is from 1976

SOURCE: thread getting caught around bobbin case

It isout of time you need to time it.by adjusting the screw on the bobbin holder turn it left or right and the tension knobe and foot tension.

SOURCE: Bobbin tension on Viking 350 Sewing Machine

Viking bobbin case tension adjustment:
When the bobbin runs out, sometimes it bends the bobbin case tension spring. Then tension is too light. Take the bobbin case out of the machine. Tie the loose bobbin thread to the Designer 1 needle plate. Insert the bobbin in the bobbin case. Here’s the tricky part set the bobbin case on the table as if it’s in the machine (Bobbin is visible and sitting horizontal to table top) threaded as if sewing and loose end tied to needle plate (that is removed from the machine). Lift the bobbin case off the table rotate it so that the flat side of the bobbin are vertical to the table and no longer horizontal. Have the bobbin case oriented so that the thread coming out of the bobbin case sprint (slot area where it is put for sewing) is at the top. Lift it high enough that the needle plate is lifted from the table. It should not release thread unless you shake it gently and then a very small amount of thread. The needle plate is the exact weight resistance your bobbin case should have on the thread.

SOURCE: Singer Sewing Machine model 9224. Bobbin thread

If you turn the handwheel, can you see a metal ring rotating around the outer edge of the bobbin case? If not rotating, broken gear or timing belt off.
If that ring is turning, remove the needle plate and bobbin case. As this ring now rotates, you will a finger on the ring that will pass behind the needle from right to left and it should catch the thread from the eye of the needle. If this finger, the "hook" passes above the eye, you have a timing problem.

Let me know.

SOURCE: Manual for older kenmore sewing machine

Manual Here: http://www.managemylife.com/mmh/lis_pdf/OWNM/1006108L.pdf

SOURCE: How to replace the tension spring in a bobbin case?

There are two springs on the bobbin case of a rotary hook machine like the 180 and I suspect you're talking about the thread tension spring on the outside of the case - this is held on and the tension adjusted by a two very small screws. The other spring is the brake spring which is a complicated shape spring that sits in the bottom of the case and puts a slight amount of pressure on the bobbin itself. Assuming the thread tension spring has been recovered along with its two screws, it should be fairly self-evident how it fits back onto the bobbin case - the spring lays across the **** in the bobbin case, through which the thread is pulled, so that the tip of the spring with a small right-angle bend just sits down into the aperture where the thread comes out. Now, importantly, the two screws are different sizes ... the one with the smallest head holds the spring onto the bobbin case and is screwed-down firmly through the hole in the flat end of the spring. The larger screw adjusts the thread tesnsion and is screwed through the hole with the slight conical sides. Now the tension should be adjusted to 5g using a proper gauge, but failing that, insert a bobbin loaded with a thread such as Metrosene and thread the bobbin case up. hold the end of the thread so that the bobbin case hangs on the thread - it should not move/unreel itself. If it does, adjust the tension screw (the bigger one) a little bit at a time until it doesn't unwind. The approximately correct tension is obtained when the bobbin will only unreel when you **** the thread upwards gently. You can fine adjust the tension to get the correct balance by ensuring the top tension is set to normal (red line) and adjusting the bobbin tension until the stitch lays properly in the fabric - use different colours top and bottom to check this. Be aware that the bobbin thread tension varies quite alot with only a small rotation of the adjusting screw, so take it is small steps.
Hope this helps.