How do you change the speed on a typical sewing machine2603 ?

This would be a problem with the foot control. It needs cleaning or replacing. This link says it has a maximum speed setting

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Without being able to personally troubleshoot, analyze, and diagnose the screeching, no one is going to be able to solve the problem.

That said, for your understsnding of the gravity of the situation, I provide the following info and warnings!!!!!

Loud screeching like you describe is INDICATIVE OF either a pulley-belt joint slipping at very high speed, OR a BEARING in a high speed application binding, NEITHER OF WHICH IS GOOD!!!!!

To prevent possible total destruction of your machine, I strongly suggest the you unplug it UNTIL you can get it to a QUALIFIED repair TECHNICIAN for troubleshooting.

The symptoms you describe are indicative of a very serious problem which could result in severe damage to your machine!

try these links and see if they can help you with a manual

Typical GC6 1 D3E

http://www.sewingindustrialmachines.com/

GC6 1 HIGH SPEED industrial sewing machine new

It sounds like the computer has lost the program. What model do you have?

Welcome to the world of industrial machines. As you are discovering they are not like a home machine. Typically these machines have either a clutch motor or if you are lucky a servo motor.

If you have a clutch motor there is typically a knob that allows you to slow it down. Or sometimes the pully needs to be replaced to "step down the speed"

A digital servo motor is a bit more complicated and you'll need to find some instruction on how to use it. But they can be easier to control. I've provided a video of the servo motor I have and recommend. (I sew heavy leather)

I have 1 pdf somewhere for a smart servo motor that might help. If yours is a servo, be careful because I got mine to run backwards once. lol Good luck

it's possible that something is loose or worn slightly to make the noise

Undo the foot control and take out the small square suppressor and throw it away, you don't need it anymore.

• Sewing machine has been run at a low speed for an extended period of time.
• To prevent overheating, motor power is automatically turned off.

Turn power off and wait about 20 minutes. Safety device will reset, and machine will be ready to operate, If this by chance doesn't work, Here is a diagram of a typical sewing machine. This fuse should be in the back next to the power box or motor

i am not familiar with the brother safety device myself. however things i would check might be to first check the manual for the machine. if not available try to turn the machine off if it is electronic in hope that it would reset itself. i would also totally unthread the machine and change the needle. embroidery machines need to have needles changed more often due to their high speeds.What type of fabric were you sewing on? Some of the newer machines are just not made to sew on very heavy fabrics and this might be causing something in side to spring. Try to stitch on a lighter fabric with a stabilizer under it