1206 footprint inside a Chinese in-line smps. Amber colour showing an underlying zigzag track like pcb trace inductor and a tiny fuzzy bit. In series with 15K , only, and going between the coldside pre-rectifier hf ac and the 48V dc output . Does not measure 0 ohm, not a fuse in that situation. Overlay marked ED201 , ED = electrostatic discharge? Note, its on the cold side. "surface mount" "spark gap" in goomages threw up nothing Bad solder joint on the v reg should be the problem but just wanted to check what this new-to-me device might be. Case cracked open painlessly
looking under x30 it has a gold coloured if not gold plated surface with a bit of ptrofiling, perhaps hiding another surface under as seems continuous metalling from land to land, with a tiny brown dot in the middle and clear plastic cover over
What a plonker. Now it is knocking out 48V DC, its function is obvious. It would have been much more obvious if it was not at the edge of the board with the L missing off the overlay designation ED201, and a more obvious window in the casing.
One time we used a series of gas tube spark gaps for protecting the circuitry, but could not figure out why they weren't meeting spec and firing closer to 400 V than over 600, until...some enlightened person suggested that maybe it was because we stuck them inside a dark oil tank and there was no light! yes, that was it. Later we noticed the problem went away when the gas was somehow 'pretriggered'. and didn't matter whether in light or dark. Radioactive isotope doping?
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