TCS Pune

NM-D521 – Bench Power & Signal Checklist

Board-specific bench checklist derived from 1 supplied source PDF(s). Source coverage: High. Verify exact thresholds, pin numbers and rail tolerances against the source schematic and component datasheets before component replacement or voltage injection.

V4.7 · REVISION SAFETY

NM-D521 · Rev 1.0

Verify the physical motherboard revision before using this checklist. Measurements, component values and power circuitry can change between revisions.

I verified the physical board revision is Rev 1.0.

Only one published revision is currently stored for this board. Verify the silkscreen before proceeding.

🔌 NM-D521Expert⏱ 60-180 minutes📋 5 steps

Compatible models: Lenovo Ideapad 3-15ALC6 HS461 HS561A HS761 SCH

⚠ Safety: Disconnect battery before resistance/diode checks. Use current limiting for injection. Never inject voltage into an unknown rail until its safe voltage/current limit and isolation path are confirmed. Use a short ground spring for high-speed oscilloscope probing.

🛠 Required Tools

Digital multimeter Oscilloscope with x10 probe Bench power supply with current limit Thermal camera / freeze spray as required SPI programmer where firmware diagnosis is required

0 / 5 done

1Confirm board identity and fault conditionRecord exact board code/revision, reported symptom, adapter/battery condition, and whether the board is in G3/S5/S0 or cycling.⚠ Use the exact board revision; similar board codes can use different power ICs.
2Unpowered resistance / short checkWith all power removed, check main input, always-on rails, memory rails and CPU/GPU rails for abnormal resistance to ground. Compare with known-good behavior when available.⚠ Low resistance on CPU/GPU core rails can be normal. Do not inject voltage until the rail topology and safe limit are confirmed.
3Trace the chronological power sequenceUse Table A in order. Stop at the first missing prerequisite, then diagnose upstream rather than replacing downstream components.⚠ A missing downstream signal is often a consequence, not the root cause.
4Capture dynamic signals with oscilloscopeUse a x10 probe and short ground connection. Capture power-button, sleep-state, reset, SPI, PWM and bus activity under the actual failure condition.⚠ Avoid long probe ground leads on switching nodes and high-speed buses.
5Record repair and verify all functionsAfter repair, repeat the failed stage, complete the sequence, test charging, battery, display, ports, thermal behavior, sleep/wake and multiple cold boots.⚠ Do not mark solved until the original symptom is reproducibly cleared.

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Schematic-derived bench record

Bench Manual & Source Coverage

Source coverage: High. Values and thresholds must still be verified against the exact schematic/datasheet.

Source PDF(s): Lenovo Ideapad 3-15ALC6 LCFC HS461_HS561A_HS761 NM-D521 Rev 1.0 SCH.pdf

Board profile

Power & Control Architecture

Platform / ODMLCFC

CPU / SoCAMD Renoir

MemoryLPDDR4

EC / SIOIT8227VG-128-CX

ChargerBQ24780SRUYR

Table A

Chronological Power Sequence

Follow upstream to downstream. A missing later signal may simply be the result of an earlier missing prerequisite.

#	Stage	Signal / Rail	From -> To	Ref	State	Expected	DMM	Oscilloscope
1	DC Input	Adapter / DC-IN main rail	Adapter/battery input path	Schematic p.40	Follow chronological sequence	19-20 V typical for barrel adapters; USB-C depends on PD contract	Measure to ground at input connector/fuse	Flat DC; inspect ripple only if unstable
2	DC Input	Input fuse - both sides	DC jack -> protection path	Schematic p.34	Follow chronological sequence	Same voltage on both sides of input fuse	DMM DC at both fuse sides to ground; continuity with power removed	Flat DC
3	Charger	ACDET / adapter detect	Adapter divider -> charger IC	Schematic p.42	Follow chronological sequence	IC-specific adapter-detect threshold; commonly about 2-3 V	DMM DC at ACDET	Flat DC
4	Charger	ACOK / AC_PRESENT	Charger -> EC/PCH	Schematic p.34	Follow chronological sequence	Valid logic state when adapter accepted; commonly logic high	DMM logic level	Clean logic transition when adapter is inserted
5	Charger	ACDRV / input MOSFET gate drive	Charger -> input MOSFET gates	Schematic p.42	Follow chronological sequence	Gate drive above source when input path is enabled; exact value IC-specific	Measure gate and source; compare VGS	Gate should rise cleanly after valid adapter detect
6	Battery	Battery positive / system battery rail	Battery connector -> charger/system	Schematic p.40	Follow chronological sequence	Pack voltage appropriate to cell count and state of charge	DMM DC at battery positive to pack ground	Flat DC; no excessive ripple
7	RTC	RTC / CMOS supply	RTC source -> PCH/SoC	Schematic p.40	Follow chronological sequence	Typically near 3 V; board-specific	DMM DC	Flat DC
8	Always-On	3 V always-on rail	Standby regulator -> EC/PCH/logic	Schematic p.3	Follow chronological sequence	3.3 V nominal where this rail exists	DMM DC at inductor/output cap	Flat DC with low ripple
9	Always-On	5 V always-on rail	Standby regulator -> peripherals	Schematic p.3	Follow chronological sequence	5.0 V nominal where design provides always-on 5 V	DMM DC at inductor/output cap	Flat DC with low ripple
10	Always-On	1.8 V auxiliary rail	Standby regulator -> BIOS/PCH/logic	Schematic p.3	Follow chronological sequence	1.8 V nominal where used	DMM DC	Flat DC
11	EC / SIO	32.768 kHz RTC / EC clock	Crystal/oscillator -> EC/PCH	Schematic p.8	Follow chronological sequence	Stable 32.768 kHz where external low-frequency clock is used	DMM not reliable; use scope	Stable low-amplitude sine/square waveform near 32.768 kHz
12	Memory	DDR VDD / VDDQ	Memory regulator -> DIMM/SoC	Schematic p.3	Follow chronological sequence	DDR generation-specific rail; verify schematic and memory generation	DMM DC at memory inductor	Flat DC; low ripple
13	Memory	DDR VPP	Memory regulator -> DIMM	Schematic p.4	Follow chronological sequence	Typically 2.5 V for DDR4; generation-specific	DMM DC	Flat DC
14	CPU / SoC	VR_ON / CPU VR enable	EC/PCH -> CPU VR controller	Schematic p.3	Follow chronological sequence	Active before CPU core rail starts; logic level is board-specific	DMM logic level	Clean enable edge
15	CPU / SoC	VR power-good	CPU VR -> EC/PCH	Schematic p.3	Follow chronological sequence	Asserted after CPU VR outputs are valid	DMM logic level	Clean assertion after core rail rises
16	Power Good	SYS_PWROK / ALL_SYS_PWRGD	PGOOD logic -> PCH/SoC	Schematic p.9	Follow chronological sequence	Asserted only after required S0 rails are valid	DMM logic level	Clean delayed assertion
17	BIOS / SPI	SPI_CS#	PCH/SoC/EC -> SPI flash	Schematic p.17	Follow chronological sequence	Idle high with access pulses during firmware reads	DMM not diagnostic; use scope	Chip-select pulse bursts during start-up
18	BIOS / SPI	SPI_CLK	PCH/SoC/EC -> SPI flash	Schematic p.8	Follow chronological sequence	Clock bursts during firmware access	DMM not diagnostic; use scope	High-frequency clock bursts
19	Display	eDP HPD	Panel -> GPU/PCH/SoC	Schematic p.5	Follow chronological sequence	Valid HPD logic state when panel is connected and powered	DMM logic level	Clean logic level/transition
20	Display	Backlight enable	EC/PCH/GPU -> panel/backlight	Schematic p.34	Follow chronological sequence	Active logic level when backlight should turn on	DMM logic level	Clean assertion after panel power

Table B

Bench Reading & Fault Isolation

Enter the actual DMM reading and scope/logic observation. Select PASS, FAIL or N/A, then tick Checked when that row is complete.

0 / 20 checked

Checked	#	Signal / Rail	Failure Isolation Hint	Technician Notes
Checked	1	Adapter / DC-IN main railSchematic p.40	No rail: inspect adapter, jack, fuse, protection MOSFETs Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	2	Input fuse - both sidesSchematic p.34	Drop/open: replace only after checking downstream short Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	3	ACDET / adapter detectSchematic p.42	Wrong level: verify divider, charger VCC and exact datasheet threshold Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	4	ACOK / AC_PRESENTSchematic p.34	Missing: validate ACDET, charger supply, pull-up and charger IC Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	5	ACDRV / input MOSFET gate driveSchematic p.42	No drive: check ACDET/ACOK, CMSRC and charger protection state Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	6	Battery positive / system battery railSchematic p.40	Abnormal: verify pack, connector, BATFET and charger path Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	7	RTC / CMOS supplySchematic p.40	Missing RTC can block RSMRST# and standby sequencing Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	8	3 V always-on railSchematic p.3	Missing/shorted: inspect standby controller enable and rail resistance Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	9	5 V always-on railSchematic p.3	Missing: inspect enable, controller supply, MOSFETs and load short Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	10	1.8 V auxiliary railSchematic p.3	Missing may block flash/PCH/EC logic on newer platforms Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	11	32.768 kHz RTC / EC clockSchematic p.8	No clock: inspect crystal, load capacitors, supply and oscillator pins Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	12	DDR VDD / VDDQSchematic p.3	Missing: check enable from S4/S3 logic and resistance to ground Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	13	DDR VPPSchematic p.4	Missing may prevent memory training; check VPP regulator/switch Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	14	VR_ON / CPU VR enableSchematic p.3	Missing: EC/PCH has stopped sequence; inspect previous power-good signals Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	15	VR power-goodSchematic p.3	Missing: inspect VR feedback, phase faults, overcurrent/thermal protection Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	16	SYS_PWROK / ALL_SYS_PWRGDSchematic p.9	Missing: identify which upstream PGOOD/rail is absent Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	17	SPI_CS#Schematic p.17	No activity: sequence, reset, clock or controller may not have reached firmware fetch Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	18	SPI_CLKSchematic p.8	CS toggles but no clock: inspect controller/bus; no bus activity: trace sequence first Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	19	eDP HPDSchematic p.5	Missing: panel/cable/connector power or HPD trace issue Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence
Checked	20	Backlight enableSchematic p.34	Missing: lid/Hall state, graphics sequence, panel detection or firmware Additional readings Resistance to ground (Ω)Diode mode (V)Current consumption	Technician evidence

V4.0 · BOARD COMPONENT INTELLIGENCE

Component Index

Select a board component to see its function, related rails/signals, enable and power-good dependencies, input/output path, matching checklist tests and identical fitted ICs found on other board checklists. Unknown values are left unknown rather than guessed.

V4.3 Bench PSU Current Profile

Board Current Sequence

Record current draw in amperes at each observable stage. Historical comparison uses successful repairs of this exact board checklist. A different reading is a clue, not a component diagnosis.

Current sequence: No readings yet

Adapter connectedANo successful-repair baseline yet

StandbyANo successful-repair baseline yet

Power-button pressANo successful-repair baseline yet

CPU initializationANo successful-repair baseline yet

BIOS activityANo successful-repair baseline yet

POSTANo successful-repair baseline yet

Tip: enter only stages you actually observed. For boards that never reach a later stage, leave that stage blank rather than entering a guessed value.

V4.4 Board Knowledge

Previous Solved Cases

Historical cases are diagnostic references only. Confirm readings on the board in front of you before replacing parts.

Live match: Mark a bench signal FAIL to check previous solved cases for NM-D521.

No structured solved-repair knowledge has been collected for this board yet. New V4.4 solved cases will build it automatically.

V4.5 · SIMILAR BOARD / PLATFORM MATCHING

Reference Boards

Reference only: The boards below share one or more stored platform attributes with this motherboard. Their voltages, component locations, designators, sequence details and repair findings are not automatically treated as facts for the current board. Verify against the current board schematic, boardview and measurements before use.

REFERENCE BOARD

LCFC NM-D522_REV 0.2_AMD PDF

3/5 shared matching attributes

Same charger ICBQ24780SRUYR
Same EC / SIOIT8227VG-128-CX
Same platform / ODMLCFC

Open reference checklist →

REFERENCE BOARD

NM-E541, NM-E451

Revision: 1.0

3/5 shared matching attributes

Same charger ICBQ24780SRUYR
Same EC / SIOIT8227VG-128-CX
Same platform / ODMLCFC

Open reference checklist →

REFERENCE BOARD

NM-B701

Revision: 0.1

2/5 shared matching attributes

Same charger ICBQ24780SRUYR
Same platform / ODMLCFC

Open reference checklist →

REFERENCE BOARD

NM-C871

Revision: 0.1

2/5 shared matching attributes

Same charger ICBQ24780SRUYR
Same platform / ODMLCFC

Open reference checklist →

REFERENCE BOARD

NM-D562

Revision: 1.0

2/5 shared matching attributes

Same charger ICBQ24780SRUYR
Same platform / ODMLCFC

Open reference checklist →

REFERENCE BOARD