F4901 1.1a 24v Schematic Jun 2026

typically used in industrial automation, specialized printers, or networking equipment.

: The letter 'F' indicates a Fuse . On complex multilayer motherboards (such as those engineered by Wistron, Compal, or Quanta), the number 4901 is a unique location code assigned by the hardware designer. It helps technicians pinpoint the component's exact layout position using a Boardview file. f4901 1.1a 24v schematic

This is the "smart" part of the schematic. Resistors R5 and R6 form a voltage divider. When the output exceeds 24V, the TL431 (U3) conducts more current. This current flows through the LED inside the PC817 optocoupler. The phototransistor side of PC817 pulls the FB (feedback) pin of the primary IC low. The IC responds by reducing the ON-time of Q1, lowering the output voltage. This creates a stable 24V ±2%. It helps technicians pinpoint the component's exact layout

While rated for 24V, many DC systems (especially automotive) experience "load dump" spikes. If your rail might exceed 24V, you should place a in parallel with your load, after the F4901. When the output exceeds 24V, the TL431 (U3)