Over the weekend the several month old Krups burr grinder stopped working. I spent a few minutes checking that all of the hoppers were tight and the safety switches were engaged. It looked like the safety sensor on the whole bean hopper was a little farther down than it should have been and after playing with it a little it fell into the grinder housing. Due to time constraints I was forced to drink the pre-ground Caribou Guatemala that was sitting in our cupboard. While drinking I checked the warranty and found out that this grinder carries a one year warranty from Krups, but then it has to be sent to a Krups repair center...
Tonight Joe and I decided that the need for coffee and the inability to find an affordable NSF certified replacement coffee grinder was reason enough to fix this thing. I figured this was a simple safety switch, I can hear the mechanical switch click when the ground hopper is inserted.
If you decide to follow along through the pictures and do this with your own grinder be aware that we are in no way responsible for you electrocuting yourself, breaking your grinder, starting a fire or anything else that might happen as a result of you reading or following this. If you want it fixed send it in to Krups for warranty work or get a new one.
Figure 1: Grinder that does not work because the safety switch for the top cover is no longer triggered by the plastic lid.
After removing the top lid, ground hopper, and keystone (turn right just like the arrow says) you can turn the grinder on its side with the grind selector facing you. If you have somehow not unplugged the grinder now would be an excellent time to do so. This selector is probably the most difficult piece to remove and is easy to break. Using a very thin screwdriver push the silver tabs in toward the center of the selector. Three of these tabs can be found evenly spaced around the selector, one about 45 degrees to the right and left of the selector point and another 180 degrees around from the point. While pressing these tabs down pull firmly up on the selector knob and continue around the tabs until the entire selector knob slides out.
Figure 2: Here is the selector knob after being removed, notice one of the tabs on the lower edge. Watch out for the spring and plastic nub which are used to simulate the clicking selector motion and possibly help keep the grind setting from changing during grinding.
Figure 3: Remove the outer plastic housing of the grinder by sliding it over the entire grinder, it is secured by four stealth plastic tabs. Apply firm pressure to the inside of the grinder where the ground hopper usually sits (note where my left thumb is). While doing this pry using a thin flat head screwdriver at the space between the inside and outside housing. You can identify the location of the tabs by the manufacturing marks on the edge of the housing.
Figure 4: Continue to work your way around the grinder (here I am on tab #2) until the outside housing is free of the tabs. Then simply slide the outside housing up and off the grinder.
Figure 5: With the housing off the PCB and brushed metal housing will lift slightly and fall forward. Notice the sensor for the top lid is visible on this picture. The screws were not properly tightened and the switch had slipped to the side causing the plastic cylinder which triggers the safety to fall through and not activate the switch. Remove the two screws holding this in place and set the safety assembly aside.
Figure 6: Two screws can be found holding the whole bean hopper and funnel shaped keystone housing in place. Remove these and lift the bean hopper off, joe took this opportunity to wash this piece.
Figure 7: A nice view of the AC motor which powers the Krups grinder, this grinder performs pretty well for our purposes but is obviously direct drive with no gearing involved. I have heard of other complain about jamming in this grinder but I have never experienced this.
Figure 8: With the whole bean hopper removed, turn the cup selector knob to its upright setting (about 6 cups) and the bushed metal plate should easily slide over the selector knob.
Figure 9: I had planned to remove the safety from the upper lid so two cuts and the switch is out of the picture. First attempt tin and solder the two wires together (remember your shrink tube) using my cold heat iron. This thing is possibly the most useless solder iron I own and it only seems to work for lighting up large solder pads on a PCB. A fun waste of time while waiting for my real solder iron to heat up...
Figure 10: Tin the ends of the two wires after stripping back about 1/8 of an inch of insulation. Tinning is the process of heating the wire and allowing it to absorb a small amount of solder. After tinning heat and place both ends together in such a fashion that the stripped and tinned parts are side by side and form a continuous wire with overlap. See ASCII Figure 11 below since I forgot to take a picture.
Ignore the dots, blogger and I are not getting along on this right now...
Ensure you have a strong solder joint with complete contact between the wires the length of the stripped and tinned area. Slide your shrink tube over the joint and apply heat to shrink.
Figure 12: A somewhat poor picture to end with but the wire has been bundled with the others and it is time to reassemble the grinder.
Proceed to re-attach the whole bean hopper and secure it with two screws. Place the PCB inside the two notches on the top of the bushed metal plate and slide the entire assembly onto the grinder carefully fitting the PCB and plastic key of the cup selector into their respective slots. The brushed metal plate and whole bean hopper should be quite sturdy and secure at this point if all was reassembled correctly. Check that no wires are hanging in the way of the motor or in the way of the external plastic housing sliding over the grinder. Carefully insert the spring and plastic nub for the grind selector into their cylinder and slide the external housing over the grinder. The external housing should slide on easily and snap securely into its final position. Turn the square grind selector shaft to its farthest clockwise position and snap the grind selector knob back into place set to the Coarsest setting.
Fixed and look at that there is no need for that pesky plastic top to be in exactly the right position anymore!
What does a coffee grinder have to do with things "On The Back Side"? We drink a lot of coffee on the back side (Kenya AA and Caribou Fireside) and we are quite picky about how we drink it. This could be the biggest threat late night cuts ever faced.