No wonder why this thing is getting scorched. A few successive flashes at full power when the zoom head is at the widest position causes the temperature of the lens to exceed 100 °C!
(as measured on my thermal imager)
What I don't get is how the flashtube can be cracked like hell and still be working.
Yeah. I'd assume this is due to repeated thermal shock. Over the service life of this flashgun, it's been fired thousands of times at full- or near-full-power when I covered events like my college athletics' Annual Awards Banquet.