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Nie, dziękuję Przekieruj mnie tamHello, could you tell me what type of FET or triac is originally in it and whether there is an insulating plate between the heat sinks and the components mounted on them? Thank you, have a nice day!
• The power-switching device that usually fails on the Miele W2241 electronic module is not a stand-alone FET or a classic triac but an integrated offline-switcher IC from Power Integrations (TinySwitch-II / TinySwitch-III family). In >90 % of boards examined the marking is TNY266PN, TNY267PN or TNY268PN (DIP-8B package, internal 700 V MOSFET).
• The board also carries several triacs that drive mains-side loads. The most common factory-fitted types are:
– BTA16-600B/CW (motor / heater) – insulated TO-220AB tab
– Z0109MN / BT136-600E (small valves, door lock) – bare TO-220 / TO-202 tab
• Wherever the metal tab of the device is electrically live (TinySwitch, BT136, etc.) an electrically insulating but thermally conductive interface is fitted between the device and the aluminium heat-sink (grey silicone “Sil-Pad”, mica washer + thermal grease, or a clip-on Kapton film). Devices supplied in an already insulated package (suffix “B” or “W”) may be bolted directly to the sink, but the washer is still present on many boards to equalise pressure and improve heat spreading.
Key points
Topology of the W2241 control board
• Primary SMPS: Half-wave fly-back supply around a Power Integrations TinySwitch IC. The IC integrates a 700 V MOSFET (Drain on pins 5-8 and on the exposed tab). Loss of this IC gives the classic “dead machine / no display” symptom.
• Mains-side actuator drivers: One to three triacs on a larger “cold-plate” style sink control drum motor (phase angle), circulation pump and heater relay bypass.
• Logic side: 5 V and 12 V rails derived from the SMPS, microcontroller, opto-isolated gate drive to triacs.
Why it is not usually a discrete MOSFET
In domestic appliances the cost and EMI constraints favour off-line switcher ICs rather than two-chip solutions (PWM controller + discrete FET). Miele followed the trend and moved from the Philips TEA1522T in older boards to Power Integrations TinySwitch in ELP/EDPL series boards shipped with the W2241.
Triac selection and package variants
• Motor/heater triac: 16 A, 600 V, logic level, e.g. ST BTA16-600CW (isolated 2500 V RMS insulation built into the package, RθJC≈1.7 K/W).
• Auxiliary triacs: 1 A–4 A devices, typically non-isolated tab (BT136-600E, Z0109MN). These require an extra mica/Kapton pad unless the sink is floating at the same potential.
• Controlling method: opto-triac drivers (MOC3051/MOC3063) to achieve galvanic isolation from MCU.
Thermal and electrical interface
• For the TinySwitch IC the metal tab sits at HV DC (~325 V after bridge). To comply with SELV and EMC the pad must withstand at least 3 kV. Silicone elastomer pads (Bergquist Sil-Pad 1500, thickness 0.25 mm) are commonly used.
• Pads are retained with a spring clamp or a nylon screw/spacer; thermal grease is not applied on pre-greased silicone pads, but is essential on mica or Kapton washers.
• Board copper under the sink is usually tinned and left floating; the sink itself may be connected to primary-side EMC ground via a Y-capacitor.
Consequences of omitting the insulator
• Direct short of HV Drain to earthed/primary ground → instant destruction of the new IC, fusible resistor, bridge and often PCB trace vaporisation.
• EMI failure (radiated common-mode) and excessive leakage current to chassis.
• Appliance makers now migrate to PI’s LinkSwitch-TN2/3 and InnoSwitch families which integrate better standby efficiency and SR control.
• For load control many manufacturers replace triacs with 600 V/40 A GaN FET half-bridges in BLDC motor inverters; however, traditional universal-motor machines like the W2241 continue to use triacs.
• Thermal interfaces increasingly use phase-change pads (lower thermal impedance, automated placement).
Example marking table (observed on three W2241 boards):
| PCB silkscreen | Measured part marking | Function | Insulation method |
| SMPS_SW | TNY267PN | 5 V/12 V supply | Grey silicone pad + clip |
| TR1 | BTA16-600CW | Motor | None (package is fully insulated) |
| TR2 | BT136-600E | Pump | Mica washer + grease |
Analogy: Think of the insulator as the “rubber sole” of an electrician’s shoe—allows heat (your body) to pass reluctantly but blocks the dangerous voltage from reaching the conductive ground.
• Working on mains-side circuitry requires competence and compliance with IEC 60335-1 (household appliance safety).
• Repairs that defeat insulation barriers may expose users to lethal voltages and can void CE conformity.
• Disposal of failed power semiconductors must follow local WEEE regulations; lead-bearing solder joints demand RoHS-compatible handling if reworked.
Identification
– Photograph the component area, clean with IPA, read full top line.
– Cross-check with the TinySwitch or triac datasheet (pin-out, tab potential).
Replacement procedure
– Desolder, clean pads, inspect for ring cracks.
– If the original was TNY266-268: fit exact or next-higher current grade.
– Replace the fusible resistor (22 Ω–47 Ω, 2 W) and the 47 µF/400 V bulk cap if ESR is high.
Re-mounting to heat-sink
– New silicone pad or intact original; pad must cover the entire tab area.
– Apply 0.1 mm-thick thermal grease layer if using mica.
– Tighten to 0.4–0.6 Nm; overtightening bows the package and lifts the die.
Verification
– Bring board up on an isolation transformer and series bulb; check for 5 V rail before reconnecting to the appliance.
– Confirm no mains potential on heat-sink relative to PE ground with >1 MΩ DMM.
Potential challenges and remedies
• Silk-screen scrubbed → use circuit topology to identify IC.
• Pad torn → cut replacement from Sil-Pad or Kapton + grease.
• PCB scorched → mill away carbonised FR-4, use wire jumpers.
• Miele occasionally used a TEA1522T controller in early revision boards; this SO-14 IC is not heat-sunk. If that is your board, the question of an insulating plate does not apply to the SMPS controller but only to the triacs.
• Part numbers above are representative; always validate against the physical board you have—Miele revises boards without changing the appliance model number.
• Obtain the official service manual for ELP-171/172 or EDPL-151 boards (available from Miele trade portal or professional forums).
• Power Integrations application note AN-23 (TinySwitch-II design) for understanding failure modes.
• IEC 60747-8 (triac) & IEC 60664-1 (insulation coordination) for design margins.
• Investigate GaN-based replacements for triacs in future high-efficiency designs.
The “mystery transistor” on the Miele W2241 power board is normally a Power Integrations TinySwitch (TNY266-268) containing its own HV MOSFET; high-current loads are switched by BTA16-series triacs. Because the metal tab of the TinySwitch and of non-isolated triacs is at hazardous voltage, the factory fit includes a thin silicone or mica insulating pad between device and heat-sink. Preserve or replace this insulator whenever the component is changed—omitting it will instantaneously destroy the new parts and create a shock hazard.
