The 7-Year Bug That Took 3 Minutes to Fix

Bored tech, warehouse cable, and a 'this was obvious' pile-on spark drama

TLDR: A rail safety device had a ghost glitch for seven years until a bored tech used a 400m cable, revealing noise that a bigger capacitor fixed in minutes. Comments split between empathy and “this was obvious,” with calls to test like the real world and add field diagnostics.

Seven years chasing a ghost fuse-blower in a rail safety device, and the hero wasn’t a fancy oscilloscope—it was a bored tech with a forklift and a 400m cable. The long wire reproduced the failure instantly, and the fix—adding a bigger capacitor to soak up noise—took three minutes. Why did it fail? The warehouse‑length cable acted like a noise magnet, fooling the safety check and tripping the fuse.

The loudest chorus: test like the real world. As readthenotes1 deadpanned, "we need to test with a real world cable..." Fans crowned the forklift a mascot for hands‑on realism. Then came the spice: bryanlarsen’s "This post makes you look incompetent" jab, followed by a self‑own and a fight over hindsight vs humility.

The mood swung when Fred27 shared a heartbreak: a bug took so long that the original user had died before the fix. Cue collective pause—this isn’t just about gadgets; it’s about people depending on them. Practical minds piled in: jasonpeacock asked why no field measurements, citing safety rules. Meanwhile, jokes flew: "Forklift‑driven development," "long cable cosplaying an antenna," and calls to give the warehouse tech an honorary degree. Final vibe: persistence matters, luck helps, and sometimes boredom saves the day.

Key Points

  • A safety-critical railway inverter at ENA Tecnologia intermittently blew its fuse due to false safety triggers.
  • The issue could not be reproduced in the lab for seven years despite varied test conditions.
  • Connecting a 400-meter cable reproduced the fault immediately by introducing inductive noise.
  • Noise coupled into the safety detection circuit was misread as a fault by redundant electronics.
  • A larger filter capacitor to ground fixed the issue in minutes, and the device has worked reliably since.

Hottest takes

"we need to test with a real world cable..." — readthenotes1
"This post makes you look incompetent" — bryanlarsen
"he'd died of natural causes in the meantime" — Fred27
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