Hi everyone,
Thanks for the feedback to date on my problem.
A little more info to clear up a couple of items being discussed.
The sewing machine is approximately 30years old, its a Pfaff 1222 model and has been a little trooper over the years never missing a beat, well until now that is. As for the parts being 40+ years old, I don't know, maybe Mr Pfaff hasn't changed his design in a while at the time. When I opened it up and saw the full scale components I thought that this was going to be an easy fix, until I noticed the third leg on the capacitor.
I took the picture of the circuit board removed from the sewing machine, if you look closely there is nine pin lugs at the bottom of the circuit board that wiring attaches to. The only circuit diagram I have at the moment is what I found under the terminal box lid, and it only shows the wiring leaving this board via these pins. Not sure what the switch that pins 7,8 and 9 go to is, it may be something to do with making the machine go forward and reverse.
**broken link removed**
As for the wiring you see in the original photo, the blue wires go to the power plug which the sewing machines foot plugs into, and I believe these wires carry the speed signal (which I think is a simple resistance). While the two black wires are coming from the power switch (secondary side), the wiring between the power switch and plug (same one that the foot plugs into is not in the photo).
Finally, in the original photo there is a small glass fuse (2Amp) which I had removed before taking the shot, which as you would expect was well and truly blown.
The topic about earthing got me curious, sewing machine has a three pin power plug (i.e earthed) however this goes to the foot pedal which then has a four pin lug which attaches to the sewing machine. From what I can work out, two of these pins are for the power supply (240Vac Active/Neutral), with the remaining two used to carry the speed signal, which I believe is nothing more than a resistance from a potentiometer in the pedal. Which leaves me wondering how the sewing machine body which is steel is being earthed. The two coils in the centre of the board share a iron core so this is probably an isolation transformer. They seem so small for such a duty, would this make sense?
I have googled for a schematic diagram for the circuit board but have had no luck, and have not had time to reverse engineer one for it yet.
So, I'm still at a bit of a loss for what to do next. What is the public opinion on the necessity of the capacitors with this additional info? Particularly with regards to the fact that I can't identify a bonded earth to the machine.
Thanks heaps,
Peter.