: 47µF, 35V Ceramic or Tantalum Capacitor.
). If your meter reads "OL" (Open Loop) or infinite resistance, the fuse is blown and must be replaced. 3. Checking for Downstream Shorts
: Part of the power distribution for the LCD interface.
When debugging a circuit board featuring an F4901 fault protection block, look out for these three common failure modes: 1. The Circuit is Completely Dead (Zero Volts Downstream) f4901 1.1a 24v schematic
: The main system power rail ( VIN or +19V_ADAPT ) feeds directly into the display subsystem.
often makes the schematic easier to find than the power supply part number alone. Can you provide the brand name type of equipment this power supply belongs to?
Directly preceding the fuse, you will typically find parallel decoupling capacitors (often marked as C4901 or C4902 ). These capacitors smooth out high-frequency noise from the power supply, ensuring that voltage ripples do not cause premature thermal fatigue in the fuse element. 3. Protection Element (F4901) : 47µF, 35V Ceramic or Tantalum Capacitor
If a downstream short-circuit occurs but the fuse takes several seconds to isolate the fault, check for improper PCB heatsinking or insufficient power supply current capacity. If the 24V power supply sags or enters hiccup mode before providing the necessary Itripcap I sub t r i p end-sub
For exact pinouts and related power rails (like the 19V or 3.3V lines), consult the official JE50_SB Schematic PDF . Related Motherboard Components On the JE50_SB board, you may also encounter: PL9201: A power inductor often associated with GPU voltage. BIOS Chip: Frequently identified as MX25L1605 .
Switch your multimeter over to resistance mode and probe between the output pad of and system ground. If the reading is close to , a ceramic decoupling capacitor is shorted to ground. 5. Sourcing and Replacing the Component The Circuit is Completely Dead (Zero Volts Downstream)
Usually indicates a short circuit on the secondary side (the 24V output) or a failed feedback loop, causing the PWM controller to restart repeatedly. Bulging Capacitors:
If the F4901 uses a 0.6V reference (common in modern LEDs), the formula to get 24V is: Vout = Vref * (1 + R1/R2) 24.0V = 0.6V * (1 + R1/R2)
: Ensuring the 1.1A limit is strictly adhered to prevents overheating and potential fire hazards in 24V systems.
: If a laptop has a working external display but no internal backlight, F4901 is a primary "blown" suspect.