If you measure 0V at the current sense resistor, inspect the input protection MOSFETs. Check if 19V is present at the drain but missing at the source. Measure the gate voltage; if it is 0V, the charging IC is intentionally keeping them shut due to a short-circuit downstream.
Use the schematic to find the CPU buck converter coils. Measure if the processor is getting its core voltage.
Check the gates of the entry MOSFETs. If the gate voltage is missing, the charging IC is either not powered, missing its ACIN/ACOK signal, or detecting a short circuit on the B+ rail. lqv77 laptop schematics
Most LQV77 repair packs include a .cad or .brd boardview file. Opening this in a viewer like OpenBoardView allows you to click on a net (e.g., +3VALW ) and instantly see every single component connected to it—from the charging IC to the audio codec.
Many LQV77 schematics are distributed as or .BRD files compatible with software like BoardViewer or OpenBoardView . Look for filenames such as: If you measure 0V at the current sense
Use your oscilloscope or multimeter in max-hold mode to probe the main voltage coils ( PL designators). Check if the memory power ( +1.2V_VCCM ) or secondary rails switch on briefly. A short circuit on a minor rail (like a shorted ceramic filtering capacitor on a +3VS line) will trigger the over-current protection (OCP) of the PWM controller, causing an immediate shutdown. Scenario C: Liquid Damage Near the Audio/IO Section
The step-down voltage pathways transforming raw battery or DC-in power into highly regulated, low-voltage lines. Use the schematic to find the CPU buck converter coils
: They use standardized electrical symbols for resistors, capacitors, and transistors to clarify the electrical continuity of a circuit OpenTextBC .
If your bench power supply shows high current draw immediately, you’ll use the schematic to identify which capacitors are linked to the main power rail (B+ or VIN).