SDG #358 AxxSolder - Open Source JBC Soldering System

The AxxSolder is a DIY, fully open source controller for JBC C115, C210 and C245 cartridges, built around an STM32 and a 240x320 TFT. It exists in two mechanical variants sharing one PCB: a compact portable enclosure (the version tested here) and a bench version that mates with a genuine JBC cradle. Power can come from USB-C PD or a plain DC input, and the handpiece connector uses pin bridging so the firmware can identify the cartridge family and set appropriate power limits.

The most useful part of this review is the schematic critique. The thermocouple front end uses a fast chopper-stabilised op amp with substantial gain but no feedback capacitor to roll off high frequency response, leaving it prone to picking up nearby switching noise. More seriously, a capacitor sits directly on an op amp output, a classic recipe for gain peaking, phase inversion and oscillation. Both are cheap fixes: a small feedback cap, and either a series resistor to form a proper RC filter or deleting the cap entirely and feeding the ADC directly.

Performance-wise, USB-C PD negotiated 20V but the board reported only 100W even from a 140W-capable supply, and cold heat-up was noticeably sluggish. Switching to an external 24V supply pulled around 5.5A and transformed ramp time, with a 10cm solder coin test showing roughly 75W sustained and no sign of thermal shortfall.

Usability niggles are firmware-level rather than fatal: presets cannot be stored with a long press, and reaching the settings menu requires a power cycle while holding the encoder. The portable case is also easy to knock off its sleep contact, so the cradle-mounted build looks like the better bench choice.