Board-specific bench checklist derived from supplied schematic source(s) for 820-03286 . Only signals located in the supplied schematic text were added automatically; missing thresholds or values remain technician-verified rather than guessed.
⚠ 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. Verify board/revision before using reference values.
🛠 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
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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): 820-03286.pdf
Board profile
Power & Control Architecture
Platform / ODMApple MLB
CPU / SoCApple SoC platform
PCH / ChipsetSoC integrated
MemoryUnified memory / SoC platform
EC / SIOSPMU / SMC
ChargerMandola charger reference
CPU VRIceman VR reference
BIOS / SPISoC QSPI flash
USB-C / PDApple USB-C port controller / Ace3 ecosystem
GPUSoC integrated
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
Input connector / protection path
Schematic p.34
Follow chronological sequence
Board-specific adapter/input voltage; verify source/PD contract and schematic.
Measure DC to ground at the adapter/input protection path.
Flat DC; investigate collapse or excessive ripple.
2
EC / SMC
32.768 kHz RTC / EC clock
RTC / EC low-frequency clock
Schematic p.45
Follow chronological sequence
Stable low-frequency oscillation where the board exposes/measures it.
Oscilloscope with high-impedance probe; avoid loading crystal nodes.
~32.768 kHz waveform when applicable.
3
Memory
Memory VDD / VDDQ
Memory power
Schematic p.3
Follow chronological sequence
Nominal board-specific memory rail voltage for installed memory generation.
Measure rail voltage at memory coil/capacitors.
Stable DC with normal ramp.
4
BIOS / SPI
BIOS / SPI flash supply
SPI flash supply
Schematic p.117
Follow chronological sequence
Use exact flash marking/datasheet; commonly 1.8 V or 3.3 V but never assume.
Identify exact flash device first, then measure VCC.
Stable DC.
5
BIOS / SPI
SPI chip-select
Controller -> SPI flash
Schematic p.3
Follow chronological sequence
Idle/inactive with access pulses when firmware is being read.
Oscilloscope during power-on/reset release.
Chip-select pulse bursts.
6
BIOS / SPI
SPI clock
Controller -> SPI flash
Schematic p.3
Follow chronological sequence
Clock bursts during flash access.
Oscilloscope during firmware access.
High-frequency clock bursts.
7
Display
LCD / eDP panel power
Panel power switch -> connector
Schematic p.82
Follow chronological sequence
Board-specific panel logic supply as shown in schematic.
Measure at panel connector/fuse/load switch.
Stable DC after panel enable.
8
Display
Backlight PWM
EC/PCH/GPU -> backlight controller
Schematic p.91
Follow chronological sequence
PWM activity when brightness is nonzero; exact frequency/duty is platform specific.
Use oscilloscope; measure duty/frequency.
Stable PWM waveform.
9
USB-C / PD
USB-C CC1 / CC2
USB-C port -> PD controller
Schematic p.32
Follow chronological sequence
Valid CC attachment/orientation state; exact voltage depends on source/sink role and Rp/Rd.
Measure CC states according to Type-C/PD controller datasheet and port orientation.
Observe attach/orientation changes.
10
USB-C / PD
PD negotiation / contract
USB-C PD controller
Schematic p.3
Follow chronological sequence
Contract may be 5/9/15/20 V or PPS depending platform/source; do not assume 20 V.
Verify 5 V default VBUS first, then observe negotiation and final contract.
PD communication / VBUS transition when negotiation succeeds.
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 / 10 checked
Checked
#
Signal / Rail
Measured
Observed Waveform / Logic
Result
Failure Isolation Hint
Technician Notes
1
Adapter / DC-IN main railSchematic p.34
No input: inspect adapter/port, fuse, protection MOSFETs and shorted PBUS/system rail.Additional readings
Missing PWM with enable present: inspect brightness control source and firmware/EC path.Additional readings
Technician evidence
9
USB-C CC1 / CC2Schematic p.32
Abnormal state: inspect port, ESD/protection, pull networks and PD controller supply before IC replacement.Additional readings
Technician evidence
10
PD negotiation / contractSchematic p.3
No contract: verify CC state, controller supply, dead-battery path, firmware and source/cable compatibility.Additional readings
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.
Controller / IC
BIOS IC · SoC QSPI flash
Function
SPI firmware flash memory
Related rails / signalsNot identified from current checklist.
Enable / sequencingNot identified from current checklist.
PGOOD / statusNot identified from current checklist.
Input
Controller
Output
SPI flash
Checklist tests
BIOS / SPI flash supply u2014 Use exact flash marking/datasheet; commonly 1.8 V or 3.3 V but never assume.
SPI chip-select u2014 Idle/inactive with access pulses when firmware is being read.
No other published board checklist currently uses this exact stored IC part number.
No matching components found.
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
No successful-repair baseline yet
No successful-repair baseline yet
No successful-repair baseline yet
No successful-repair baseline yet
No successful-repair baseline yet
No 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 820-03286.
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 matches are discovery aids only. Missing information on this board is deliberately left unknown and is not filled from a similar board.
V4.9 Diagnostic Timeline
Repair Timeline
Bench actions are recorded in sequence for training, QC and future troubleshooting. Signal result changes remain in history even after a failed stage later passes.
The final solved forum case receives the complete timeline for this bench session. Manual actions should describe what was actually done, not a suspected cause.
GUIDED BIOS DIAGNOSTICS · V5.1
BIOS / SPI Flash Diagnostic Record
Record only measurements observed on this board. The workflow does not assume a flash voltage, logic level or firmware fault from a single reading.
Original BIOS dump
The first uploaded original is locked to this diagnostic session and cannot be overwritten by this workflow.
Repaired BIOS dump
Stored as a separate attachment. Uploading it never modifies the original dump.
Final diagnostic decision
Is the problem solved?
Complete the applicable checklist and bench rows first. If solved, the completed diagnostic flow is converted into a resolved Repair Forum post automatically.
Repair QC & Final VerificationRequired before solved publication
Every item must be PASS, or N/A with a reason. Any FAIL reopens the repair and blocks the solved forum post.
V5.0 Repair Case Intelligence
Board Repair Dashboard
Aggregate repair patterns for 820-03286. Historical patterns are references, not proof of the current fault.
0Recorded repairs
0.0%Solved
Not enough timeline dataAverage diagnosis time
0Rework cases
Common symptoms
No structured data yet.
Frequently failed rails / signals
No structured data yet.
Frequently replaced / repaired ICs
No structured data yet.
Common root causes
No structured data yet.
Diagnosis time is calculated from V4.9 timeline evidence when available. Only server-recorded board-linked repair cases are counted; unsaved local bench sessions are excluded. Technician performance is never exposed on this board dashboard.
USB-C / PD DIAGNOSTICS · V5.2
USB-C Power Delivery Diagnostic Record
Record observed behavior on this board and adapter. Contract voltage and controller behavior vary by platform; this module does not assume that a higher-voltage PD contract must always be present.
USB-C port fault checklist
Check only what was actually inspected. A failed item is a diagnostic clue, not an automatic component diagnosis.
DISPLAY / NO-DISPLAY DIAGNOSTICS · V5.3
Internal & External Display Diagnostic Record
Record board-specific observations. Missing display signals are clues only; expected voltage, polarity and timing must be verified from the schematic, panel specification or known-good board.
Internal vs external display decision tree
Complete the checks in order. The guidance below narrows the next area to inspect but does not declare a component faulty.
Record the internal and external display results to show decision guidance.
💰
Estimated repair cost at TCS Pune
₹4,000 – ₹15,000
Final price confirmed after free device inspection. Includes 6-month warranty.
