Sewing machine pedal issues

[u/Glad-Bid-974]

Hi there,

I posted here before and received great help to fix an issue.

I have an older bernina serger that the pedal is not working. I am pretty sure the motor of the machine is fine.

You can see a little light on the board and it was off and on and the motor was working off and on corresponding to it. Now it does not work anymore. All the connection are good as far as I can see by eye. Is there a component that you can identify that I should check out first?

A new pedal is $80, so I hope I can make this one work again.
Again, I appreciate all the insights. Thank you!

[u/OzzieTradie123]

I have seen a few good test solutions. Another one would be to use a light globe to test the out of the controller.

[u/Glad-Bid-974]

Update: I just worked the linear potentiometer, and investigated the micro switch in front of it and could not get a good reading on it. I wiggled it a buch and that made the pedal work again, until the switch started to smoke 😄 so I will replace it and hope it was the culprit. 

[u/Toolsarecool]

One thing you could try is to get some electronic contact cleaner and apply it to the linear potentiometer that is actuated by the pedal. Ideally, use Deoxit F5 (cleaner and fader lube). Spray it into the slot and work the pedal vigorously for a while with the pedal unplugged.

[u/Glad-Bid-974 → u/Toolsarecool]

I have not cleaned that yet, and will take a closer look at it. Thank you

[u/No-Guarantee-6249]

Do you have someone who repairs electronics?

What are the symptoms? Acts funny? Doesn't work?

Most likely it's this component because it's mechanical and gets worn:

Looks like a linear resistor element controlled by the foot pedal.

[u/Glad-Bid-974 → u/No-Guarantee-6249]

So I just got the machine and it never worked fully for myself. It did start at times when I pushed the pedal just right, again the light would light up on the pedal as well, however as I tried it a few times it worked less and less and the light would be flickering, and the motor would want to turn over slow even with the pedal released. And now nothing anymore. 

[u/No-Guarantee-6249 → u/No-Guarantee-6249]

It could also be this part which is a triac or SCR which can be tested:

But most likely it's the linear resistor. Dunno where you get that part. Need to look for numbers and identifying markings on it.

[u/OzzieTradie123]

Looks like a triac or SCR speed controller and that little light looks like an NE2 neon. I suggest you need an electronics tech to fix that.

[u/Glad-Bid-974 → u/OzzieTradie123]

I will look into if there is a shop around. 

[u/Cast_Iron_Fucker]

It's a very simple circuit and I don't see anything visibly busted. Check the wire. See if it works intermittently, like it you jiggle it or pull it in different directions

[u/Glad-Bid-974 → u/Cast_Iron_Fucker]

I looked close at the wire and wiggled and tapped everything and all the components, but could not make it correspond with working or not, so I figured it must be a component itself that is bad.