The Lamp Room

I measured the temperature of one of my sign lights today. The canopy was 80c and the ballast over 100c! I don’t think these ballast have an internal thermal cut out but I’m not sure. If they do, the cut out temp would probably be around 155c. If the tubes were rectifying the ballast temp would likely be higher.

I’m quite surprised the heat didn’t dim down the tubes too?, I bet that temperature changed the supply specs to the tubes too?

I’m quite surprised the heat didn’t dim down the tubes too?, I bet that temperature changed the supply specs to the tubes too?

I didn't notice any dimming down of the tubes but they were certainly running a lot hotter than usual. The cathodes were glowing brighter blue and phosphor degradation would be increased if it was like this all the time.

During normal conditions the ballast temperature is probably only around 70c and in the winter even less. Having my sign lights on 24/7, the ballasts are certainly hammered.

I wonder if that was a result of the overheating gear that was causing the tubes to run brighter?, Can’t remember what catalogue I’ve read it in now, (think it was Osrams)?, but it states ballasts should not be allowed to overheat as this change’s the current they supply the lamp.
Of all the years of discharge street lighting, I wonder how many lamps were slightly overrun on hot summer nights?