The TOP suspect is a marginal neutral return.
This return leg/ or grounding conductor will read 'fine' on a DMM, even a small analog meter.
Once loaded the voltage differential will collapse...
Then see Scott35, above.
The poor neutral can exist MERELY by being too far from the panel -- resulting in excessive impedance.
While the neutral is the TOP suspect, even the 'hot' (120V) may have too much impedance or too much of a parallel load. ( much more uncommon: 'make-up' on neutrals is very commonly much more sloppy than the 'hot' conductor.)
In your case, I would not be surprised if the load was wired off a 'house' panel. (on the landlord's dime) This will usually be a dinky panel back near the Service entrance -- with just perhaps ONE circuit dedicated to this lighting run. (count up the fixtures on this circuit -- too many and you're into 'multi-vibrator land.')
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I've seen this 'multi-vibrator' effect on every manner of electronic 'ballast' or power conversion logic -- especially in site lighting where the distances are LONG.
Upsizing the conductors -- especially the neutral solves the problem, nothing else.
The very size of your building is suspect: this particular fixture 'smells' like it's very far from your distribution panel.
It's as common as dust for the installation crew to NOT spot the voltage drop because of impedance on such long neutral runs -- which will, obviously, never be line of sight.
I've seen this defeat countless foremen and j-men.
Multi-vibrators are worth studying on Wiki just for an understanding of engineered flip-flops.
By the way, your computer utterly depends upon multi-vibrator logic, they always have.
As intelligent devices pervade our lives, you'll encounter this frustrating tick more than once.
And, with this, you're the 'smartest wire-man' in your complex!
Last edited by Tesla; 01/25/15 02:42 AM.
