Crafty's Old Board — Cleaning Flux and Ink Stopped the Runaway Heating
The board pulled from Crafty after the unresolved temperature warning went back on the bench to see whether it could still be used. With no airflow it overheated past 85 °C and was still climbing. After two isopropyl cleanings it levels off at 72 °C. It has not been flown, and nothing was tested under battery or motor load.
vtx_power = 1 (25 mW), with the AUX6 power mapping cleared and VTX PIT MODE (mode 39)
always on (aux 4 39 0 900 2100 0 0). That is not “off”: Betaflight has no VTX off. Unplug the
board between tests.The board
BETAFPVG473_V2 on the BETAFPV dev firmware 2026.6.0-alpha, craft_name = Crafty,
vcd_video_system = AUTO, osd_displayport_device = MAX7456, gyro ICM42622P at 8 kHz, 47 %
CPU. The gyro separates it from the replacement board,
which has a BMI270. The MCU ID was not read.
Photos showed the battery-lead pads (+ and –) coated in black baked flux, with uneven solder
around the R001 shunt. The pink tint is marker ink used to colour parts, which dissolved into
the flux. It is not damage.
Bench temperatures
USB only, no battery, no motors. Core temperature from status, sampled every 12–15 s.
Core temperature, no fan, old Crafty board
Cleaning the flux and ink slowed the climb and lowered the plateau. USB only, no battery. Hover for values.
Show as a table
| Time | Not cleaned | First cleaning | Second cleaning | Repeat run |
|---|---|---|---|---|
| 30 s | 77 °C | 58 °C | 52 °C | 53 °C |
| 60 s | 83 °C | 67 °C | 56 °C | 58 °C |
| 120 s | 71 °C | 64 °C | 66 °C | |
| 180 s | 73 °C | 68 °C | 69 °C | |
| 240 s | 74 °C | 70 °C | 71 °C | |
| 300 s | 74 °C | 72 °C | 72 °C | |
| 360 s | 75 °C | 72 °C | ||
| 420 s | 74 °C | 72 °C | ||
| 500 s | 75 °C |
| Condition | Core temperature |
|---|---|
| Not cleaned, no fan | 66 → 85 °C in ~2 min, still rising (stopped at the 85 °C cutoff) |
Not cleaned, fan on, pid_process_denom 4 | 45 °C, flat |
| After first cleaning, no fan | 37 → 70 °C in ~85 s, then 74–75 °C for ~7 min |
| After second cleaning, no fan | 45 → 68 °C in 3.4 min, then 72 °C flat (73 °C last read) |
| After second cleaning, repeat from cold, 6 min | 48 → 72 °C at 5 min, then flat (73 °C last read) |
| Replacement board, no fan (23 Sep) | 63–65 °C at 3.5 min |
The 17 September bench reading of this board, a 72 °C plateau, matches the second-cleaning result. Only the uncleaned run looks like a fault. Each cleaning lowered the plateau and slowed the climb, which points at the residue, though the starting conditions differed from run to run.
Halving the PID rate (pid_process_denom 2 → 4) changed nothing: CPU stayed at 47 %. The 8 kHz
gyro loop cannot be lowered on this board.
What is and is not known
Known: the runaway heating went away after cleaning. The board is stable with the fan on (45 °C) and plateaus at 72 °C without it. Config, gyro and OSD are intact.
Not known:
- Whether flux and ink leakage was the whole cause. It is the likeliest reading, not proven.
- Which cleaning did what: both were done between runs.
- Current draw, motor outputs and DShot telemetry. No battery was connected.
- Flight behaviour. On 17 September the alarm tripped in flight at low VTX power.
72 °C is still above osd_core_temp_alarm = 70, so on the bench without airflow the warning
still fires.
Outcome
Usable as a bench and programming board. Before flying it:
- Fit a VTX antenna, remove the always-on pit mode (
aux 4 0 0 900 900 0 0) and restore the AUX6 power mapping. - Run a props-off battery test for current draw and all four motor outputs.
- Fly a short pack and read the temperature on the OSD. If it warns, raise
osd_core_temp_alarm(about 85) rather than chasing it. The replacement board’s 63–65 °C shows the airframe is not the problem.