2024-06-29 - Fixing the Starter on an Old Sewing Machine -------------------------------------------------------- WARNING: All the standard warnings apply. In particular, unplug everything before working on the electrical parts of the sewing machine. WARNING: I'm not an electrician, so take everything here with a grain of salt. A while ago, I decided to take a closer look at my grandparents' old Pfaff 260 Automatic sewing machine[0]. This sewing machine mainly worked as it should, the only problem was the starter[1], activated by a foot pedal. The problem was that there were essentially two speeds, on and off, which made sewing with it quite difficult. I first tried to fix the starter, but eventually decided to get a different one. I still want to mention a few important parts of the disassembly/reassembly in case anyone else wants to attempt that. WARNING: The starter on this type of sewing machine is directly connected to mains voltage, so be very careful when working on it. First, the piece connecting the starter to the foot pedal needs to be unscrewed from the foot pedal[2]. Then, the actual starter can be taken apart. I performed this disassembly almost half a year ago, so I don't remember everything, I just know that quite a few screws needed to be removed, and the lever activating the mechanism also had to be removed first (the spring holding it up can just be unhooked from the frame). There also is padding around some screws that can easily fall out, so make sure you remember where that goes. Once the starter is open, the mechanism can be seen[3]. The way it works is that there are some sort of carbon plates which are pressed together by the lever mechanism, causing the resistance to drop[4]. As can be seen in [3], there is also a regular contact piece in the middle that eventually bridges the contacts directly without going through the carbon plates. If the resistance of the carbon plates is too high even when they are pressed together, electricity will only flow once the contacts are bridged in the middle, essentially making it an on-off switch. In this case, the plates at the very end were completely corroded[5]. I removed the completely corroded plates, cleaned the other parts, and put everything back together. One more note is that the contact piece in the middle can be adjusted[6] so it is further away from the contacts, meaning that they are only bridged after the carbon plates have been compressed further. Of course, if it's too far away, the contacts may never be bridged, which would also be an issue. The reassembly is very annoying because the screws need to go into the right holes while at the same time, the part that the lever is later attached to needs to be pushed against the force of a strong spring so it also goes in the right hole. It works best to stick a screwdriver through the hole in the case where the lever is attached so it can be used to push the part inside against the force of the spring. I noticed one design "feature" where the filter capacitor is located[7]. There is a long screw in each of the four corners. Three of them are regular screws, but one of them only has a winding going about half the way, with the rest of the screw just being smooth. This screw needs to be in the corner with the filter capacitor because the smooth part presses against the capacitor. This could have easily been avoided by either making the case just a tiny bit bigger or by moving the capacitor away from the screw. The latter option isn't possible now because the capacitor is held in place by a screwed-down holder. The holder can be rotated a bit, but I'm pretty sure I tried that and it didn't make it any better. Maybe this is what they call German Engineering. I guess it would probably be a good idea to replace the capacitor with a proper modern safety capacitor anyways, but I ended up getting a new starter, so it doesn't really matter. After I went through this ordeal, the starter worked slightly better, but it was still very difficult to get any speed between off and full speed, so I decided to get a completely new starter. Another option could have been to replace the carbon plates, but it seems to be fairly difficult to get those at a reasonable price. I couldn't find any starters of the same type (other than used ones for way too much money), but there are plenty of cheap foot pedal controllers you can buy. I got one with the model number YDK YC-190 for about 20€. It would have been ideal to get a separate power cable and connect that to the new starter, but this sewing machine uses an old Pfaff-specific power plug[8] that you can only get used for way too much money, so I decided to cut apart the original power cable. I decided to make the old and new starter swappable, so I attached standard IEC 60320 C13/C14 connectors[9] to the cables. One important note here is that the cable on the side of the starter should have the inlet (i.e. C14, with the exposed pins). The cable coming from the sewing machine has live mains power running across it, so there should not be any exposed pins on that side. [10] shows the inlet for the old starter. Note that the grounding wire in the middle should be a bit longer than the other wires as an additional safety mechanism so it tears after the other wires in case they are torn out. The new starter didn't have a grounding connection, so the middle pin on its inlet could just be left without any connected wire. Finally, a connector had to be attached to the cable coming from the sewing machine. The connections inside the new starter were made using the clamps that came with it[11]. There was also some extra insulation that could be added around the connections[12]. After all that work, I was left with two interchangeable starters[13], although I don't know why anyone would want to use the old starter anymore. [14] shows a short demo of the new starter. On this sewing machine stand, it's actually possible to optionally attach a wheel to the original foot pedal so the machine can be operated without electricity. It might be a good idea to connect that wheel so the original foot pedal can be used for operating without electricity, while the new starter can still easily be attached if electricity should be used. For now, though, I'm just happy that the sewing machine can be used normally again. [0] gopher://lumidify.org/I/phlog/2024-06-29-sewing-machine/sewing_machine.jpg [1] gopher://lumidify.org/I/phlog/2024-06-29-sewing-machine/old_starter.jpg [2] gopher://lumidify.org/I/phlog/2024-06-29-sewing-machine/pedal_connection.jpg [3] gopher://lumidify.org/I/phlog/2024-06-29-sewing-machine/old_starter_mechanism.jpg [4] gopher://lumidify.org/I/phlog/2024-06-29-sewing-machine/ceramic_piece_plates.jpg [5] gopher://lumidify.org/I/phlog/2024-06-29-sewing-machine/bad_plates.jpg [6] gopher://lumidify.org/I/phlog/2024-06-29-sewing-machine/contact_adjustment.jpg [7] gopher://lumidify.org/I/phlog/2024-06-29-sewing-machine/capacitor.jpg [8] gopher://lumidify.org/I/phlog/2024-06-29-sewing-machine/plug.jpg [9] gopher://lumidify.org/I/phlog/2024-06-29-sewing-machine/connectors.jpg [10] gopher://lumidify.org/I/phlog/2024-06-29-sewing-machine/old_starter_inlet.jpg [11] gopher://lumidify.org/I/phlog/2024-06-29-sewing-machine/new_starter_clamp.jpg [12] gopher://lumidify.org/I/phlog/2024-06-29-sewing-machine/new_starter_wiring.jpg [13] gopher://lumidify.org/I/phlog/2024-06-29-sewing-machine/new_starter_connected.jpg [14] gopher://lumidify.org/9/phlog/2024-06-29-sewing-machine/demo.ogv