Dismantling & Service Walkthrough
A step-by-step video guide demonstrating safe disassembly, connector mapping, servo replacement, fuse checks, and reassembly procedures for maintenance and troubleshooting.
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Dismantling video placeholder
Video Chapters
00:00 — Intro & Safety
Power disconnect procedure, safety precautions, tools required
01:10 — Head Module Removal
Camera and MG996R servo wiring, ribbon cable disconnection
03:45 — Upper Body PCA9685
Access to PCA board bank, channel mapping verification, I²C cable checks
06:20 — Lower Body Power
Buck converter access, fuse inspection, ground plane verification
09:50 — Arduino & Serial Links
UART cable verification, Arduino board inspection, heartbeat diagnostics
12:30 — Reassembly Tips
Connector labeling best practices, cable routing, final assembly sequence
Safe Disassembly Procedure
Power Down & Disconnect Battery
Use the main power switch. Wait 10 seconds for capacitors to discharge. Disconnect battery terminals (red first, then black).
Document Connector Positions
Take photos or use the PCA channel CSV as reference. Label all wiring with tape before disconnecting.
Disable E-STOP (if holding mechanism)
Some E-STOP buttons hold power. Ensure it's in safe state before proceeding with disassembly.
Remove Servo Wiring Methodically
Work from top (head) to bottom (legs). Three-pin connectors: match pinout carefully. Keep connectors together with their wires.
Inspect Joints & Mechanical Components
Look for physical damage, loose screws, corrosion, or misalignment. Check servo gears for wear.
Reassemble in Reverse Order
Connect power last. Use photos and labels from step 2. Apply thermal paste to buck converters if reinstalling heatsink.
Connector Reference
Servo Connectors (3-pin JR Style)
Pin 1: Signal (Yellow/White)
PWM from PCA9685 or Arduino
Pin 2: Power (Red)
6.2V (upper) or 6.5V (lower)
Pin 3: Ground (Brown/Black)
Common ground to battery
I²C Bus (PCA9685)
SDA (Pin 2)
Data line (pull-up to 3.3V)
SCL (Pin 3)
Clock line (pull-up to 3.3V)
GND
Common ground
UART (Arduino Mega)
TX (Pin 1)
To Pi RX (GPIO15)
RX (Pin 0)
From Pi TX (GPIO14)
GND
Common ground (critical)
Power Distribution
Battery Main
12V nominal (10-14V range)
Buck Upper Out
6.2V for head & arms
Buck Lower Out
6.5V for hips & legs
Troubleshooting Guide
Servo doesn't respond after reassembly
Check PCA channel CSV to confirm correct mapping. Verify PWM signal with oscilloscope (should be 1-2ms pulses at 50Hz). Confirm servo connector polarity (yellow/red/black in correct order).
No power to servos
Check fuses first. Use multimeter to verify buck converter outputs (6.2V upper, 6.5V lower). Confirm battery voltage. Look for loose power connectors or burnt connectors.
Jittery servo motion
Likely cable routing issue. Avoid running servo power cables near I²C or UART lines. Use shielded cables if possible. Check for loose connectors on PCA board. Verify PCA9685 is powered correctly.
I²C bus not responding
Verify pull-up resistors are in place. Check SDA/SCL cable continuity. Confirm PCA board address via A5-A0 pins. Use i2cdetect command on Pi to scan bus.
UART communication errors
Verify baud rate (115200). Check TX/RX pin connections (should not be swapped). Confirm common ground between Pi and Arduino. Use serial monitor to debug packet format.
Thermal throttling during long demo
Check Pi heatsink and fan operation. Verify buck converter heatsink contact. Ensure adequate airflow around electronics. Monitor CPU temp with vcgencmd measure_temp command.