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How do you fix a juki 373,378 sewing machine that won't stop running? Answered

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Roxcnc

11 months ago

I had this happen to my Juki 550. After doing some troubleshooting I determined that a "Trisistor" had failed on the speed control board. I was able to find a similar replacement at the local electrical store. Replacing it was a bit of a pain as you have to do a bit of disassembly to access it.

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seandogue

4 years ago

UNplug it, then fix the broken switch or speed control.

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mpilchfamily

4 years ago

Unplug it. Ties it down. Cut off it's legs.

Need more details. Are you using a foot pedal? Have you pulled the peddle apart to see if anything is broken or worn out? Have you check for a service manuel on the machine?

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Downunder35mmpilchfamily

Answer 4 years ago

Cut off the legs !??
You are soooo cruel! How can you do that to living and feeling sewing machine? ;)

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Downunder35m

4 years ago

How about some more detail first?
Running means it has legs? If so try a leash ;)
But jokes aside it is usually the switch that gives up.
You know the one you control the speed with using your foot?
There are different types and I am not familiar with your model but if you take it apart you should see either of these:
a) some mechanics connected to a potentiometer or "slider" - this is "reading" the throttle position.
b) a complete set of electronics together with a) - this is usually to be found in those controllers that connect between machine and mains power.

I assume b) as it is more common.
Without seeing your internals it is hard to judge but if the machine is always running at full speed it is usually the power transistor that failed.
Depending on the type a replacement costs between 50cents and a few bucks.
Basic soldering skills required to replace.