So, you are saying the power supply wasn't properly grounded and the output was float in reference to ground. Sounds like things were not properly installed and grounded. I don't go along with the Vandergraf garbage,
You're lucky you were able to isolate it. I've seen many intermittent failures in the lab, which were impossible to reliability repeat, and thus diagnose. I suspect this is something that's very widespread, and accounts for a lot of in-the-field glitches.
Actually, the grounding precautions were not so much for the equipment, but for the safety of the developing prototypes and new product introductions.But the equipment is normally sitting right on the same bench as the product, which is the target of the precautionary measures. And yes, this was a recent practice used on manufacturing floors as late as last year when I was introducing a military computing device at a domestic OEM.
Boy does this bring back memories of grad school. We had an ultrafast-spectroscopy instrument that we assembled from $1.2 Million of lasers and fancy electronics equipment. In essence, our system was a very, very fast strobe light that would illuminate a repetitive chemical reaction at precisely the right time. We used a liquid nitrogen-cooled scientific CCD camera that would record the faint output signal viewed through a maze of optics and filters. We would darken the lab and use upwards of 20-min CCD exposures to collect the very faint signal. Every now and again our data would be extremely noisy and we would have to collect data again. After some major sleuthing, we discovered that one of the PCs on the far side of the lab running Windows3.0 had a screen saver consisting of a bouncing ball. All but the top 5% of the computer monitor was obscured by equipment and only when the image of the ball bounced near the top of the screen did the extra photons get entrained into our optics. I've disliked screen savers ever since...
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