The problem is that fuses protect against over-current, not over-voltage.

The fuse would not blow with less current than the motor required, so if it blew immediately, the electronics (at double voltage) was drawing more current than the motor would draw normally. That is not a good thing. Electronics can blow way faster than a fuse.

I think it is unlikely you can fix this without replacing the electronics, which is probably as expensive to buy as a new machine. That is why repair shops are not interested.

 

Its possible that the line voltage is routed to the transformer on the diagram. If you supply twice the voltage to the primary of the transformer then the primary would also see twice the current and that could blow the fuse. BTW, a parts supplier shows a fuse on the list of parts.

 

Its possible that the line voltage is routed to the transformer on the diagram. If you supply twice the voltage to the primary of the transformer then the primary would also see twice the current and that could blow the fuse. BTW, a parts supplier shows a fuse on the list of parts.
View attachment 295979

It will see a lot more than twice the current as the magnetics will saturate.

 

What transformer? I would think it is unlikely that a modern sewing machine would have a line transformer.

 

Take a look at electrical diagram PDF in post #19.

 

Take a look at electrical diagram PDF in post #19.

Yeah, I would expect a large transformer like that to have a primary fuse.

 

Here's the transformer and looks like a line transformer.
Appears to have dual secondary, most likely supplying electronics with one and maybe motors with other.

 

The online parts store shows most of the motors as 24V steppers driven from the CPU board. The main motor (item e) is driven from the Power Circuit assembly.
From its picture, it "smells" like a DC motor given the read/black leads and physical construction, etc.

 

The manual does not mention a fuse at all, which probably means it is mounted on a circuit board, and possibly that board is only replaced, never repaired. That means you would need to replace the fuse your self.
But if you have a meter that can measure resistance then the very first step is to measure the resistance between the two prongs of the mains connection plug with the power switch in the "ON" position.
If that reading indicates an open circuit, unplug the cord from the machine and measure for resistance between the pins of that connector. If that also reads open circuit then a fuse inside the machine has failed. Replacing a soldered in fuse demands some soldering skill .

 

The problem is that fuses protect against over-current, not over-voltage.

The fuse would not blow with less current than the motor required, so if it blew immediately, the electronics (at double voltage) was drawing more current than the motor would draw normally. That is not a good thing. Electronics can blow way faster than a fuse.

I think it is unlikely you can fix this without replacing the electronics, which is probably as expensive to buy as a new machine. That is why repair shops are not interested.

I can verify that there would be much more current if twice the voltage is applied. In addition, the motor is never powered the moment the plug is in, nor the moment that the switch is switched on.
If the TS is able to locate an honest and competent repair person , not just a module changer, that individual will be ableto locate the fault. And since there is a transformer and a power circuit board, it is more likely that the fuse is on the power circuit board.

 

I'll have a look at it for you. (Can't guarantee to fix it, though)

 

I'll have a look at it for you. (Can't guarantee to fix it, though)

Certainly an actual visual inspection by one who knows what they are looking for has a much greater chance for success. And certainly getting a report as to what was found will be useful education for the rest of us. So many thanks to Ian0 for such a generous offer. I am on the wrong side of the pond to be able to take a look.