Build · Troubleshooting

Diagnose it like an engineer, not a gambler.

When things go wrong, systematic beats frantic. Change one variable at a time and you’ll be back in the bracket; change five and you’ll never know what worked.

The diagnostic process

Step 1

Make it safe

Disconnect the battery before working on electrical systems. Any powered test with a weapon installed happens inside a test box. Never bypass safety systems.

Step 2

Power system check

Verify battery voltage (12.6 V full for 3S), the main switch, and the LED indicators on ESCs and receiver (some ESCs have no LED). Most failures start with power.

Step 3

Visual inspection

Loose connections, damaged wires, burnt components, mechanical damage — many problems are visible.

Step 4

Continuity testing

Multimeter on continuity (speaker symbol). Test each wire end to end — a beep means good, silence means a broken wire or loose connection. Confirm each board is receiving power.

Step 5

Isolate, then replace

Disconnect components one at a time, starting with whatever was most recently added or changed. Replace one component at a time to pin the failure.

Key measurements (standard kit)

What	Expect
3S LiPo (11.1 V nominal)	12.6 V fully charged · 9.0 V minimum under load
2S LiPo (7.4 V nominal)	8.4 V fully charged · 6.0 V minimum under load
Single cell	4.2 V max charge · 3.0 V minimum discharge
Brushed drive motor (standard kit)	1–10 Ω typical winding resistance · infinite to ground
Any single connection	Voltage drop should not exceed 0.2 V

Electrical failures

Symptom	Looks like	Work the list
Complete power loss	No LEDs, no response.	Check battery voltage and charge Verify the main switch connection and operation Inspect motor and power-distribution wires
Intermittent operation	Works, then cuts out randomly.	Look for loose or corroded connections Hunt cold solder joints Verify battery-connector integrity Test while flexing the harness gently
ESC beeping, won’t arm	Continuous error tones.	Recalibrate / arm the ESC with the transmitter Check the signal wire to the receiver Verify transmitter endpoint settings
Motor runs the wrong direction	Spins opposite to intended.	Swap any two motor wires (brushed or brushless) Or reverse the transmitter channel — NEVER the weapon channel Check transmitter mixing

Mechanical failures

Symptom	Looks like	Work the list
Wheels slipping on hubs	Drive wheels lose grip on the shafts.	Tighten shaft-collar set screws Threadlocker on set screws File a flat on the motor shaft Replace a worn hub with a tighter one
Binding or grinding	Unusual noises during movement.	Clear debris from the drive system and gearbox Inspect bearings for wear Check component alignment
Cracked or broken parts	Printed components with stress fractures.	Superglue small cracks as a temporary field fix Swap in spare parts — this is why you printed two Reprint properly after the event; a glued part is not a repaired part
Weapon won’t spin up	Fails to reach speed.	Check motor mounting and alignment Verify the weapon is balanced Test the motor separately from the weapon Make sure mounting screws don’t touch the motor windings

Radio & control

Symptom	Looks like	Work the list
Fail-safe not working	Robot doesn’t stop when the transmitter turns off.	Reconfigure fail-safe on transmitter and receiver Verify the receiver supports fail-safe Check the ESC fail-safe configuration Re-run the full fail-safe test before fighting
Won’t bind	No connection during binding.	Hold the bind button through the whole process Confirm the protocols are compatible Try a different model slot If you substitute a known-good receiver to isolate the fault, rebind and re-verify fail-safe before any powered test

When to stop

If a fix requires bypassing a safety system, working on a powered weapon outside containment, or a battery that’s puffed, dented, or torn — stop. Replace the component, or ask an event official for help. At events, the pit is full of people who’ve fixed the exact same failure; part lending is legal and encouraged.

Re-test after any repair →Wiring reference