It seems a bit of a lottery with these LOPT's, I think it is a very good idea to drive out any moisture by passing current through it before trying to apply power to the set.
I also remove the screening lid on these sets, in an attempt to reduce the temperature, I never liked the idea of the LOPT being encased next to the PZ30 & PL38.
The heat really builds up after a couple of hours running!
Mark