Last week I went to England to pick up my new knitting machine, a very well kept Brother 950. Coming home with my new possession I was very excited to get set up and turn on the electronics.
Before starting, as I knew that the machine had not been used for awhile, I changed the felt bar (sponge bar/needle retainer). The old one was completely flat but the one from my older KH820 machine was the same size so I could use that one to replace it.
Everything went well until approximately 5 minutes after turning it on, then there was a loud pop and smoke came out of the machine. It was completely lifeless. After some searching on the internet I found out that it most likely either had blown a fuse or a capacitor had malfunctioned and that it would probably not be so hard to fix.
Then it is nice to have a son with electrical skills that was willing to pay mom a visit over the weekend to fix her new knitting machine. In order to make this happen I had to unfasten the cover on the left side where the electrical cord is attached in order to find the size of the fuse or capacitor that needed to be replaced. To do this I needed a utility knife and two screwdrivers, one flat head and one Phillips head. To do this the three plastic rivets and the three screws holding the cover in place had to be removed. Then I could get to the screws holding the electrical cord and loosen them as well. To get the circuit board out the two screws holding the plastic retainer needed to come loose and then I could pry loose the circuit board in order to see the damaged component.
It was a capacitor that had gone bad due to old age and needed to be replaced. As these components are pretty old (at least 20 yrs) I decided to change both capacitors and the fuse, this way these components would not introduce problems again any time soon.
I bought one 100 nano Farad and another 47 nano Farad capacitor both rated for over 250 Volts as well as a 0.5 Ampere fuse. Then I was all set and could just wait for the weekend and my son to come and fix the rest.
Well home he also needed the screwdrivers earlier mentioned as well as his soldering equipment, flat nosed pliers and side-cutters. Heat the soldering iron to roughly 380 °C this makes the soldering job easy. To begin with the capacitors have to bee loosened, this is done by heating up the solder holding them in place and either by applying solder wick or using a desoldering pump removing most of the solder. The leads connecting the capacitor to the circuit may be bent and need to be forced straight for the capacitor to come loose. Once each capacitor has been removed and the connecting holes are relatively free of solder you can insert the new one, carefully bending the leads as necessary to make it fit into the holes. Make sure that you replace each capacitor with its' respective new counterpart. It makes the soldering job a lot easier to have clamps to hold the components and/or the circuit board in place. Heat up the leads and the pad around the hole on the circuit board and apply solder, this will give you a good round and shiny solder bump if done correctly. If you notice matte solder bumps take care to reheat them as the electrical connection may be weak.
It is very likely that the fuse has been blown when the capacitor malfunctioned so it is wise to replace it while you're at it.
Then all items, screws and rivets need to be placed back exactly as before. When plugged into the power socket and the power switch was flipped on the machine greeted me with a joyful "beep" and has been in great working condition since.
I look forward to posting new designs in the coming weeks made on my new knitting machine. I also have intentions to convert the electronics by performing the so called AYAB hack.
