Mechanical sewing machine (Bernina 600) repair

Safety notice: The Bernina 600 electrical motor is connected to high voltage. Make sure you know what you are doing or ask someone who does know!

Last week, we were busy browsing the web when our Bernina 600, a vintage piece manufactured in 1960, released its magic smoke, the main breaker tripped... and then no internet anymore!

We quickly disconnected the sewing machine and it was quite clear what happend: the noise filter located on the 230VAC voltage "exploded". This is something pretty common in old equipments and the difficulty is to find a replacement module.

Anyway, first thing first, removing the motor and getting hold of the filter.

Remove the 3 screws highlighted on the below picture and remove the belt.

Use a carton box where you can put the motor. Be careful with the cable under the motor. We will disconnect it later.

Remove the screw highlighted in the pict below.

You now see the filter. Remove the 2 screws holding the wires et voilà.

Pull gently the filter out of its compartment.

The other side...

As I said before, it will be difficult to find such a module. The manufacturer is "Leclanché". That company is still in business but doesn't produce this can anymore. So, I decided to make one.

You need 4 capacitors. I found them in my spare box. The values don't need to be exactly the ones written on the can BUT you must make sure they are rated for at least 250VAC. I live in a 230 VAC country!

Then, I replicated the same schematics seen on the can. I used 2x 68nF and 2x 2.2nF. That's pretty close, isn't it?

Before removing the can, make sure you write down where the wires go. You don't want to do more damage to your old machine when you solder them back later.

Add 4 wires with different colors. I took what I had. It's better if you can match the original colors.

Put some shrinking tube over the whole set of capacitors. Don't completely cover the wires. Install the module back in its compartment.

Solder the 4 wires and isolate each of them with shrinking tubes. Check carefully your connections. Put everything back together and you are done!

I tested it (well, not me!) and it works perfectly. Success!

Happy repairs