Firstly, the difference between the 285s - the old one were not 285HV.
Secondly, according to Pentax in Utah the "old" 285 is well within the safe voltage. Mine registers at 8.3 on the v-meter and Pentax said something like 13max. I had placed a note about this on the forum, way-back.
The 285 (and 283) are work-horses and much respected in the field.
UPDATED
I went back and searched for the post I refered to above. It was on 13 August 2007
Quote: Finally got thru to Pentax at 1.800.877.0155 and spoke to Derek. He says "As long as it doesn't exceed 25V..." I should be OK.