Introduction: KitchenAid KMT422CU 4-Slice Toaster Buzzer Removal and LED Modification

Introduction: Introduction: KitchenAid KMT422CU 4-Slice Toaster Buzzer Removal and LED Modification

This guide applies to all KitchenAid KMT-422 series toasters equipped with a buzzer and manual toaster levers.  The guide will provide thorough instructions on how to safely remove the buzzer.  It will also include optional instructions for installing an LED in place of the buzzer, so that the notification feature is preserved.

The buzzer is being removed because it is extremely loud and unnecessary.  This feature makes a potentially great toaster too annoying to use.

For a video guide that accompanies this written guide, go to:

For part 1:

For part 2:

Step 1: Tools

Tools required for removing the buzzers only:
1.  Needle-nose pliers
2.  Phillips screwdriver PH2 size
3.  Security bit, U-head size 3.0 or equivalent (this tool can also be home-made by grinding a notch into a flathead screwdriver)
4.  Soldering iron and peripherals (solder, sponge, stand etc, see this guide if you do not know how to solder)
5.  Soldering wick or solder sucker

(Optional) Additional tools required for installing the LED:
1.  4 pairs of male and female disconnects
2.  2 LED holders
3.  22 AWG stranded wire- about 2 feet, preferably in red and black/blue
4.  2, 5mm LEDs
5.  2, 180 Ohm 1/4 Watt resistors
6.  Heatshrink, assorted
7.  Heat gun or lighter
8.  4 inches solid core jumper wire
9.  Wire strippers
10.  Optional but highly recommended: Helping Hands
11.  Deburring tool or file
12.  Wire cutters

Step 2: Unplugging the Toaster

First, unplug the toaster. This will ensure your safety while working on the toaster.

Step 3: Removing the Crumb Trays

1.   Gently push on the crumb trays located in the back of the toaster.
2.   The trays should pop out. Remove the trays by sliding them out of the toaster.

Step 4: Removing the Security Screws

1. Carefully flip the toaster over and remove the 6 security-bit screws from the bottom.
2. The location of the security-bit screws are circled above in red.

Step 5: Lifting the Casing

1. Place the toaster back upright.
2. Gently lift the entire casing up approximately 1.5".

Note: The casing may need some force to loosen the metal tabs located within the toaster.

Step 6: Identifying the Circuit Boards

This is one of the two circuit boards that will be modified by removing the buzzer. The other circuit board (located on the opposite side of the toaster) is identical to this one.

Step 7: Removing the 8-Pin Connector

While gently pulling up on the wires, remove the 8-pin connectors located on both boards.  Prying up on the connector with a small flat-blade screwdriver may help in this process.  To ensure maximum access to the circuit boards, pull the front of the toaster up until the two levers stop the casing from opening further.

Step 8: Removing the Rubber Sleeves

With needle-nose pliers, remove the rubber coverings at the base of the red and blue wires located on the edge of the circuit board. 
These white rubber sleeves will be covering two female disconnects.

Step 9: Removing the Female Disconnects

1. Using the needle-nose pliers, grip the base of the female disconnects connected to the red and blue wires as shown.
2. Slowly pull them up until they are free from the board.

Note: The connectors will be tight. Do not be afraid to use some force, but make sure that it is directed in an upward direction to ensure that the connector and/or board are not damaged.

Step 10: Checking the Circuit Board

After completing the previous steps, your circuit boards should look similar to the picture above.

Note: Currently, we have disconnected the 8-pin connector and two female disconnects.

Step 11: Removing the 2-Pin Connectors

Using the needle-nose pliers, remove the three two-pin connectors located near the back of each circuit board. Make note of the specific location for each pin connector by using a marker, tape, or photographing the board before removal.

Step 12: Unscrewing the Circuit Boards

Using the Phillips screwdriver, remove the two screws located in opposite corners of the circuit board.

Step 13: Freeing the Circuit Board

Remove the circuit board to have full access to the buzzer. Repeat steps 8 through 13 to remove the other circuit board.

Step 14: Desoldering and Removing the Buzzer

In this step, you can use either a solder wick or solder sucker to remove the solder that is holding the buzzer to the circuit board.  The instructions listed below are written for use with the solder wick.  If you choose to use a solder sucker, follow the instructions and use a solder sucker in place of the solder wick. 

WARNING: Do not hold the soldering iron against the board or any components for more than 10 to 15 seconds.  You may damage components if they are overheated.

1.  If you do not know how to solder, review this guide to understand the terms and to practice before continuing.
2.  Place the wick against one of the solder joints on the buzzer.
3. Apply some solder to the soldering iron tip.
4. Apply the hot soldering iron to the solder wick and wait for the solder to be sucked into the solder wick from the joint on the buzzer lead.
5.  Remove the solder wick and iron at the same time.
6.  Pull the buzzer from the board.  It should come out with little effort. If it does not, reheat the joint and ensure that there is no solder keeping the buzzer attached to the board.
7.  Repeat steps 2 through 5 within "Desoldering and Removing the Buzzer" for the other buzzer lead.

Step 15: (Optional) LED Installation Introduction

If you do not plan to install the optional LED, congratulations! You are done modifying your toaster and you can skip all instructions with titles beginning with "(Optional)" and proceed to step 20.

If you do plan to install the LED modification, follow all steps including the ones with "(Optional)" in the title.  

The LED modification will replace the buzzer with a resistor and LED circuit.  The LED will light up and blink when the toast is done, preserving the notification feature of the toaster.  This procedure requires soldering, crimping, and use of heatshrink.

Below is a circuit diagram of the original buzzer circuit (left) and the new LED circuit (right) to be installed.

Note: The installation of the LED is a technical operation. It is important to be confident in your skills and abilities.

Step 16: (Optional) Making the LED-Side

To make it easy to service the toaster in the future, the LED will disconnect from the board similar to the female disconnects that were removed in step 9.  To do this, we are going to use 1/4" male and female disconnect between the board and LED circuit.

Making the board-side connectors:
1.  Remove the plastic sleeves from four pairs of male and female disconnects (Seen in red in the picture).
2.  Strip 4" of solid core wire and cut it into 4, 1" sections.
3.  Set up your soldering station. 
4.  While the iron is heating up, insert 1 of the 1" solid core wires into a male disconnect.
5.  Bend the wire around the disconnect and crimp the it onto the wire and solder it, as illustrated in the pictures.
6.  Repeat steps 4 and 5 within "(Optional) Making the LED to Board Connectors" for the other male disconnect.
7.  Insert one of the disconnects into the board from the top side and bend the tab against the back, making sure not to let it touch other pads.
8.  Solder the connector to the pad.
9.  Repeat steps 7 and 8 within "(Optional) Making the LED to Board Connectors" for the other connector.

Step 17: (Optional) Making the LED-circuit Side

1. Cut two colors, preferably red and black or blue to designate positive and ground, of wire into 4" lengths and strip 5/8” of insulation off each end.
2. Tin the ends of each wire lightly.
3. Insert the end of one of the wires into a female disconnect and wrap it around the end, as illustrated in the pictures.
4. Crimp the disconnect to the wire with pliers or a crimper.
5. Solder the disconnect and wire together.
6. Slip an appropriate length of heatshrink over the joint and use a heat gun or lighter to shrink it.  If you use a lighter, do not let the flame come into contact with the heatshrink.
7. For the other connector use a 1/8th Watt, 180 ohm resistor instead of wire and repeat steps 12 through 14 within "(Optional) Making the LED to Board Connectors."
8. Wrap the other lead of the resistor around the end of one of the tinned wires and solder them together.
9. Place heatshrink over the crimped connection, resistor, and tinned wire lead and shrink it.

Repeat this instruction for the other board.

Step 18: (Optional) Making the LED Circuit

A resistor is required in series with the LED to limit the amount of current that enters the LED.  We used a 180 ohm, 1/8th Watt resistor.  Feel free to use higher resistance value to make the LED dimmer.  We do not recommend using a resistor less than 180 ohms for risk of damage to the circuit and LED.

1. Take one of the red-wire/connector assemblies made in the last step and slide a 1" section of heat-shrink over it.
2. Twist the end of the red wire around the longer lead of the LED and solder the lead and wire together.
3. Once the joint has cooled, slip the heat-shrink over it and shrink it over the joint.
4. Take one of the black wire and connector assemblies made in the last step and slide a 1" section of heat-shrink over it.
5. Twist the wire around the shorter lead of the LED and solder the lead and wire together.
6. Once the joint has cooled, slip the heat-shrink over it and shrink it over the joint.

Repeat this step for the other board.  The finished assembly should resemble the image above.

Step 19: (Optional) Drilling Mounting Holes Into the Toaster

In this optional step, we will make the mounting holes required for the LEDs.

1.  With the boards still out of the toaster, mark a point on the toaster about 1.5" below one of the shade dials on the toaster.  Make sure that the mark is not over any internal components.
2.  Using a 1/4" drill bit, drill a hole through the sheet metal at the marked point.  Do not apply more pressure than the weight of the drill itself and start drilling slowly to prevent the bit from slipping.
3.  Repeat steps 1 and 2 within "(Optional) Drilling Mounting Holes Into the Toaster" for the other side of the toaster.

Step 20: (Optional) Installing the LED Assemblies

In this final LED assembly step, we install the LED assemblies into the toaster.

1.  Insert an LED holder into one of the 1/4" holes drilled in the previous step.  
2.  From the inside of the toaster, push the LED into the LED holder until it clicks.
3.  Connect the LED assembly to the board; the red wire connects to the lead on the board marked with a (+).

Congratulations, your LED modification is now fully installed!

Step 21: Reinstalling the Board

1. Place the circuit board back onto the holder inside toaster.
2. Screw the board in place with the 2 screws using a Phillips head screwdriver.
3. Orient the 8-pin connector and red and blue cables so that they can be reattached without strain. The long 8-pin connector should be facing towards the front of the toaster.
4.  Insert the red and blue female disconnects onto the board, the red cable should be closest to the front of the toaster.  
5.  Attach the three, two-pin connectors, matching the order in the pictures.
6.  Make sure to route the wires away from any moving parts and seams where the body of the toaster will meet the frame.

Note: The pictures have the buzzer connected to the board. In these steps, the buzzer will be removed or replaced with an LED.

Step 22: Installing the 8-Pin Connector

Lower the toaster casing to the level in the image.  Pop the 8-pin connector into place. You should hear a quiet snap as it is inserted. Be careful not to damage the board by pressing too hard.

Step 23: Seating the Casing

1. Lower the case slowly making sure it is aligned properly. 
2. If possible, grab a helper to make this step easier. Once the casing is lowered enough that the tabs touch the slots, slip each tab into the slots.  
3. Start by inserting the tabs in pairs on one side of the toaster and progressing to the other side.  

Step 24: Securing the Casing

Flip the toaster over and begin screwing the base and case together with the 6 security-bit screws. You can peek through the open spacing on the sides to help align the screws before you start screwing them in.  Do not torque the screws too tightly or you may strip them.

Step 25: Replacing the Crumb Trays

Once all the screws are in, flip the toaster over and replace the crumb trays.  Slide them into the toaster until they click and do not spring out.

Step 26: Testing the Toaster

Test the toaster for full functionality:

1. Plug in the power cord.  If you see signs of failure (smoke, sounds, etc) unplug the toaster immediately and proceed to the troubleshooting page.
2. Push each of the levers down and make sure that they latch in place and the display comes on.  If either of these do not occur, unplug the toaster and skip to the troubleshooting step.
3. Make sure that the toaster is still generating heat.  If it is, wait until the cycle stops while monitoring the toaster.  If the toaster ends the toasting cycle with the LED blinking three times (if you did the optional modification) and releases the toasting lever, it is toasting correctly. 
4.  Press the lever again, this time test that the cancel feature is fully functioning by pressing the cancel button.  If the toaster stops toasting and releases the toasting lever, your toaster is working correctly.

Monitor the toaster for the next week or so to make sure that the internals have settled correctly.

Step 27: Troubleshooting the Toaster

If the toaster does not function at all, make sure that the outlet you are using is supplying power.

If the toaster is getting power, but not functioning properly, disassemble the toaster again.

If any wire besides the 8-pin white connector are detached, refer back to step 20.
If the 8-pin connector is detached refer back to step 21.
If the toaster works, but the LEDs do not light up when the toast is done, refer back to step 15.
If the LEDs continues to not work, check the LEDs by running a current through it, by attaching each terminal of the LED to the ends of battery.

If the levers do not stay down when you push them down all of the way, disassemble the toaster and reassemble it with care. Make sure the metal tabs of the toaster levers are in line with the plastic hooks above the circuit board. It may be necessary to bend the tabs slightly to make them fit properly.

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