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Machine just turns off when working.
After one second you turn it on and it works a few seconds and again turns off
Button is green when pressing to make coffee.
AI: Do you hear any strange sounds or smell anything unusual when the machine turns off, or does any other light (like red or orange) come on?
No
AI: How long has this problem been happening? Did you clean, move, or change anything on the machine before it started?
Maybe 3 weeks.
• The symptom “runs a few-seconds, switches off, can be powered again almost instantly, green LED only” is most often caused by a degraded film- or electrolytic capacitor on the KP120 main (power-/control) board.
• Try the easy maintenance steps first (complete descaling, clean injector needle, check water-tank float and power outlet). If they do not help, open the machine and replace the control-board capacitor (typically 470 nF / 275 VAC X2 or 47 µF electrolytic, depending on PCB revision).
• If you are not equipped to perform safe mains-voltage repairs, take the unit to a qualified technician; the part is inexpensive (< €1) and the repair normally restores full function.
Symptom characterization
• Machine starts, pump and heater draw current.
• After 3-5 s the control section loses supply → appliance switches off.
• No extra LEDs, no thermal smell, restart possible within a second.
→ Indicates electrical supply collapse, not thermal-protection trip (a thermal switch needs tens of seconds to cool).
Root causes in order of probability
Why capacitor failure is favoured
• KP-series uses a cheap “capacitive dropper” power supply.
• Film capacitors lose capacity (∆C 30-70 %) after 3-5 years due to moisture ingress and thermal stress.
• The brown-out occurs exactly when the heater PWM plus pump solenoid peaks.
• Restart is possible immediately – the capacitor re-charges as soon as load is removed.
Verification procedure (multimeter & ESR meter)
• Unplug, wait 10 min for discharge.
• Remove right-hand plastic shell (Torx-10).
• Locate blue or yellow rectangular film capacitor on PCB; mark value (usually 0.47 µF, sometimes 0.68 µF).
• Desolder, measure: anything < 0.33 µF or ESR > 2 Ω confirms failure.
• Inspect 47-µF / 100 µF electrolytics for bulging; replace if ESR>1 Ω.
• Hundreds of recent repair logs (YouTube 2023-2024, forums repaircafé, iFixit) document identical KP- and Genio-series behaviour solved by replacing the X2 film capacitor.
• Manufacturers have begun switching from capacitive droppers to isolated fly-back PSUs in newer 2024 models to avoid this aging mode.
• Environmental regulations (EU Right-to-Repair 2023/822) encourage availability of spare PCBs, so the board can also be bought complete (~€18) if soldering is not desired.
• Capacitive dropper basics: The film capacitor, together with a resistor, limits the mains current to a few milliamps for the control MCU. Capacitance \(C\) determines reactance \(X_C = 1/(2\pi f C)\). If \(C\) drops by 50 %, available control current halves; under load the supply collapses ⇒ MCU resets.
• Thermal switch logic: bimetal opens at ~145 °C, recloses around 125 °C (tens of seconds). Instant restart would be impossible; hence overheating is excluded by observation alone.
• Safety: X2-rated capacitors are mandatory (IEC 60384-14) because they are across the mains; never substitute with a standard film type.
• Warranty: KP120 is out of factory warranty (>2 y). Opening the housing voids any extended retailer warranty.
• Mains safety: Work only when unplugged; respect capacitor charge.
• Environmental: Replacing a €1 capacitor prevents scrapping a working appliance, aligning with WEEE and circular-economy goals.
Quick maintenance (no tools)
• Perform full descaling with manufacturer solution; rinse twice.
• Clean capsule holder and injector pin.
• Verify water-tank float moves and the machine is on a dedicated, grounded outlet.
Capacitor replacement (tools required)
• Tools: Torx-10 driver, soldering iron 30-40 W, desolder braid, multimeter, ESR meter (optional).
• Replacement part: 470 nF 275 VAC X2 polypropylene film capacitor, 15-22.5 mm lead pitch (e.g., Vishay MKP, Wima MP3).
• Procedure:
– Remove outer shells, disengage PCB.
– Note polarity of electrolytics; film cap is non-polar.
– Desolder old cap, clean pads, insert new, trim leads, resolder.
– Inspect for solder bridges, re-assemble, test with a water cycle (no capsule).
Possible challenges
• Brittle plastic clips – warm housing slightly with hair-dryer to avoid breakage.
• Tight space – take photos during disassembly for guidance.
• If pump startup still browns out, also change electrolytic bulk cap (47 µF/400 V) and series resistor.
• If the machine shows red or orange LEDs, or needs >30 s before it can be switched on again, the fault is likely thermal or control-logic related – follow the descaling / thermostat path.
• Some early KP120 boards use SMPS instead of capacitive droppers; in those, look for swollen electrolytics rather than film capacitors.
• Always verify mains voltage suitability of replacement components (275 VAC X2 for 230 V regions, 305 VAC X2 for 120 V).
• Investigate alternative drop-in SMPS modules for long-life replacement of capacitive droppers.
• Study the influence of water hardness on thermoblock life and energy efficiency.
• Explore open-source ECU firmware projects that add temperature profiling to KP-series machines.
The near-instant restart and absence of warning LEDs indicate a low-voltage brown-out, not overheating. In KP120 machines this is almost always caused by an aged mains-suppression film capacitor on the control board. After ruling out simple scale or float issues, replacing the 470 nF / 275 VAC X2 capacitor (or the board) cures the fault in >90 % of reported cases. The repair is inexpensive, ecologically sound, and, when performed with proper mains-safety precautions, fully restores reliable brewing.
