Funny you should ask. Last night I deemed a seed non viable so I turned everything off while I started a new seed. Or so I thought. I walked by the tent this afternoon and noticed a ton of vapor coming out of the observation vent. I looked in and couldn’t see the bottom of the tent. I forgot to turn off the humidifier. My hygrometer read almost 93%! So I opened it up for a few hours, turned on the fans, and checked the lights. I just purchased the hlg to replace my vipar. The hlg fired right up, but the vipar was flickering so I turned it off. I checked a few minutes ago and the hlg is running like a champ. On the other hand, the vipar stays on with both nobs turned off on the bloom side, full strength until I switch it on. Then it dims as usual. So if you were to do an experiment at the cost of a brand new light, my situation would fit the bill. I’m so impressed with my new light and recommend it hands down.
As for the dimmer screw, my kit came with a smaller philips head screwdriver that fits the screw head perfectly. I was a bit concerned with some posts talking about stripping too. Actually read those after I ordered it. After assembly, which is easy enough for an 8th grader, I tried the dimmer out. It turns with zero resistance! Maybe they have improved in recent models, idk, but everything about that light is exceptional. I hope that my mistake and impressions are of some help. I have no affiliation with hlg, just got lucky with research after throwing my money away on the stupid vipar. Cheers!