Note: Never inject 19V directly into a shorted rail. Use a laboratory bench power supply limited to 1V to locate the component generating heat. Symptom 2: Power Light Turns On, Then Instantly Shuts Off
Because this is a portable unit, the datasheet for the Lac391p chip may not be publicly available. In this scenario, reverse-engineering the pinout is necessary. Use the schematic to identify the VCC and Ground pins first, then trace the input/output lines.
When the power button is pressed, the Super I/O chip receives the signal and releases the secondary enable commands. Powers the RAM slots.
A corrupt flash memory can cause the laptop to turn on briefly (fan spins for 2–3 seconds) and then turn off, or show a black screen with solid power LEDs. On the LA-C391P, both the Main BIOS chip and the internal flash of the ENE KB9022Q EC might require reprogramming using a dedicated RT809F/RT809H or SVOD programmer. Liquid Damage Around the Charging Area apw70 lac391p schematic portable
PR stands for Power Resistor, PC for Power Capacitor, PU for Power IC, and PQ for Power Transistor/MOSFET. Recognizing the prefix tells you instantly what the component's basic electrical function is.
Short circuit on the 19V B+ rail or failure of the 3.3V/5V standby IC.
If the SoC is healthy and its internal clock crystal is oscillating, it responds by releasing the suspend state signals: PM_SLP_S5# , PM_SLP_S4# , and PM_SLP_S3# go high (3.3V). Note: Never inject 19V directly into a shorted rail
Embedded Controller (EC) manages the initial power-on logic before handing off control to the main chipset. Decoding the APW70 Power IC in Portable Schematics
file, which provides a visual map of where components are physically located on the PCB. Laptop schematic Official Manuals : For physical disassembly, refer to the Dell Latitude 5590 Owner's Manual Schematic Files
When the power button is triggered, the EC pulses a wake signal that enables downstream power rails: : Stabilizes the DDR4 memory system. Powers the RAM slots
The number “APW70 LA-C391P” is often confused with a specific integrated circuit, but it is the and Compal Board Number (LA-C391P) for the motherboard used in the HP ZBook 17 G3.
When repairing a portable device using the LA-C391P motherboard, follow a structured diagnostic workflow. Visual Inspection
laptop series. Finding a full schematic for "portable" viewing (typically a PDF or boardview file) usually requires accessing specialized technician databases. Technical Specifications Summary Motherboard Model: LA-C391P (often associated with the APW70 part number). Device Compatibility: Primarily found in the Dell Latitude 3410/3510 series. Processor Support:
Comprehensive Schematic Analysis of the Compal LA-C391P (APW70) Motherboard