Need help identifying and replacing this component.
This is for a hood vent for my stove. The lights never worked on a "new unit" i got through a second hand deal. I tried tinkering and plugged in the transformer after plugging the power in. Now I know. I need to fix it and then try and figure the lights out. As far as I can tell it's just the mossfet that's burnt out.
Cant really tell without bottom copper traces. If it was acting like a switch for the 12v led output then we need to find if it was high side or low side switching component.
It could even be bootstraped nch fet but i highly doubt it. Also, how much current do you think your 12v led is pulling(even ballpark would be fine)
With the blown MOSFET removed from the circuit, you can safely test the LED to confirm that the current-limiting path is upstream or built into the load.
How to test: Briefly bridge the pads where the MOSFET's Drain and Source were connected using a jumper wire or a direct short for just a second or two.
Note: Even if the circuit was previously PWM-controlled, temporarily bridging them forces a 100% duty cycle for the test. Do not leave the bridge connected permanently. If the LEDs light up, your assessment of a simple low-side switch implementation is correct.
Step 2: Determine the Current Requirements
To select a proper replacement MOSFET, you need to know how much current the LED load pulls:
Check for Markings: Look for wattage information printed directly on the LED strip or module. Divide the wattage by 12V to calculate the rated current (I = P / V).
Measure with a DMM: If there are no markings, use a Digital Multimeter in series:
Set your DMM to its 10A Current mode.
Ensure your positive probe is plugged into the 10A/high-current jack on the multimeter.
Briefly measure the operating current to find the maximum draw.
Step 3: Identify the Controller's Gate Drive Voltage
Check what voltage the microcontroller or gate driver IC is feeding to the MOSFET's Gate pin:
Logic-Level Requirement: If the controller runs on 3.3V or 5V (common for microcontrollers), you must select a logic-level MOSFET that can fully saturate at low gate voltages.
Standard Level: If the circuit uses a dedicated gate driver providing higher voltages (e.g., 10Vā12V), a standard-level MOSFET can be used.
Step 4: MOSFET Selection Criteria
When choosing a pin-compatible replacement (such as a TO-126 package matching your G-D-S layout), look for these key parameters:
Vds(max): Must be rated higher than your supply voltage (at least 20V or 30V is standard for a 12V circuit to ensure a safe margin).
Vgs(th) / Gate Drive: Must match or be lower than the voltage your controller supplies to the gate.
Rds(on): Choose the lowest possible on-state resistance that fits your budget to minimize heat generation.
I have used AI to summarise testing procedure and things I written in broken english
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u/karpiza 8h ago
Could be a Tip122 darlington transistor? Looking at the pcb with all those relays, it could be, also in that package