Repairing a faulty hand mixer - I

memochou

Repairing is misleading, I meant "attempt at repairing" but that wouldn't be a catchy title. Anyways, I have here a KitchenAid 5KHM9212BER that apparently stopped working while in use.

First thing to do was to disassemble it, which I did by just searching up a tutorial.

Disassembly

Jam a screwdriver in here and pry
Unscrew two philips screws
Now this part can be pryed open

From here you can unscrew the three screws attaching the motor to the body, revealing a PCB.

It was here that I had a problem. This PCB is attached to a ribbon cable, which connects this PCB to the knobs at the top. As far as I could tell, there's no way to detach the ribbon cable. After a bit of inspection, I found the top side can also be disassembled.

Jam a screwdriver here
Somehow unclip the 4 clips in there

The panel with the knobs can be fitted through the opening to be freed. The main PCB can now simply be pulled out.

All the components laid out

Diagnosis

I don't really know how to diagnose faulty electronics. It's not my course of study, but I do think it'd be really cool to learn. I didn't know where to start, so I referred to this website. 

I know that the fuse in the plug is intact. Upon inspecting all the electronic and electrical components, nothing seemed fried or swollen. I did find a fuse on the PCB, so that I checked.

Fuse?

I actually didn't know it was a fuse, but I saw F2 and a quick search shows the letter F designates fuses. Checking continuity with a multimeter shows that the fuse is blown. Apparently replacing the fuse doesn't fix the underlying problem, so I set out to check the other components.

Upon probing, none of the components pass any tests. In fact, none of them conducted electricity. What?

It was then I found out that PCB coatings existed. I verified it by resoldering one terminal, which took an unusually long time, then comparing it to an unmodified terminal. The resoldered terminal conducts, but the unmodified one doesn't.

Resoldered terminal is on the left
Left terminal now passes continuity
The right terminal doesn't

Now that I know that, I tried desoldering the fuse to actually check if it conducted. I mangled the fuse while doing it, but in my defense the coating made it difficult. 

There was a thin wire still sticking out the damaged end of the fuse, with which I checked the fuse for continuity. Still shows that the fuse isn't working. It could also be that in removing it I damaged the fuse to the point that it wouldn't work, but what's done is done.

Since the rest of the components would be a hassle to check because of the coating, I've decided the best I can do is simply replace this fuse. Ordering the fuse would take some time, in which I'd be on holiday when it arrives. Post holiday, the school trimester is already starting. I'm not sure when I'll have the time to fix it, but when I do I'll make a second post about it.

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