the keypad on my microwave is totally unresponsive, i have to press buttons like 10 times

Diagnosis

The unresponsive keypad on the BLACK+DECKER EM720CB7 is typically caused by a failure in the membrane switch matrix or a degradation of the conductive traces. Because this model uses a capacitive/membrane overlay, the buttons aren't mechanical switches; instead, they rely on two conductive layers being pressed together to complete a circuit. Over time, oils from fingertips, steam from cooking, or accidental spills seep through the edges of the bezel, causing corrosion or "ghosting" where the signal becomes weak, requiring multiple presses to register a command. Another common culprit is the ZIF (Zero Insertion Force) ribbon cable connector. The vibration from the microwave's magnetron and cooling fan can cause the flat gray ribbon cable to shift slightly in its socket. When the connection is marginal, the control board receives intermittent signals, leading to the "10-press" phenomenon. You can confirm this by noticing if specific buttons (like 'Start' or '30 Sec') fail more often than others, which indicates a localized trace failure, or if the entire panel is sluggish, which suggests a connection or board-level issue.

How to Fix It

To resolve a connection issue and clean the contact points, follow these precise steps:

1. Power Isolation: Unplug the unit from the wall outlet. Do not rely on the "Off" state; high-voltage capacitors inside the chassis can hold a lethal charge, but the control board area is generally safe if unplugged.
2. Case Disassembly: Remove the outer cabinet screws located at the rear and sides of the chassis. Carefully slide the metal shell backward and upward to expose the internal components.
3. Accessing the Control Board: Locate the control panel assembly at the front. Remove the small Phillips head screws securing the plastic bezel to the chassis.
4. Ribbon Cable Reseating: Find the flat, gray ribbon cable connecting the membrane keypad to the PCB. Gently lift the small black or white locking tab on the ZIF connector. Pull the ribbon cable out completely.
5. Contact Cleaning: Use a cotton swab dipped in 90% isopropyl alcohol to gently wipe the gold-plated fingers at the end of the ribbon cable. This removes oxidation and grease. Let it dry for 60 seconds.
6. Re-insertion: Slide the ribbon cable back into the slot, ensuring it is perfectly square and seated deep into the connector. Press the locking tab down firmly.
7. Testing: Before fully reassembling the shell, plug the unit in and test the responsiveness of each digit and the 'Start' button.

If That Didn't Work

• Replace the Membrane Overlay: If cleaning the cable didn't work, the internal conductive traces of the keypad have likely cracked. You will need to order a replacement membrane keypad specific to the EM720CB7. This involves peeling the old overlay off the plastic housing and adhering the new one carefully to avoid air bubbles.
• Inspect the Control PCB for Leaks: Examine the circuit board for any signs of "fish-eye" corrosion or sticky residue. If liquid spilled through the keypad, it may have created a conductive bridge on the board. Clean the board with an electronic contact cleaner spray and a soft brush.
• Check for "Child Lock" Glitches: While usually a total lockout, some firmware glitches in the EM720CB7 can make the panel feel unresponsive. Press and hold the "Stop/Clear" button for 3-5 seconds to ensure any hidden locks are disabled.
• Replace the Main Control Board: If the keypad is new and the cable is seated, but the lag persists, the microprocessor on the main PCB is failing. This requires replacing the entire control board assembly.

Heads Up

• Capacitor Warning: Never touch the large silver canister (high-voltage capacitor) inside the microwave, even when unplugged. It can store a deadly electrical charge.
• Avoid Harsh Chemicals: Never use window cleaner or ammonia-based products on the exterior keypad; these chemicals can seep under the membrane and eat away the conductive silver traces.
• Pressure Caution: When reseating the ribbon cable, do not force the locking tab. These plastic clips are brittle and will snap if pressured too hard.
• Alignment: When installing a new membrane, align the top edge perfectly first. If the overlay is skewed by even 1mm, the buttons will not align with the sensors on the board.