The mystery has since been cleared up in a different thread:
https://www.eevblog.com/forum/reviews/phillipsfluke-pm2811-power-source/So you move both the black wire on the lug marked 110 V to the 220 V
lug and the blue wire as marked in section 3.1.5 of the service manual
(from X4106 to X4102).
I can confirm that this works for moving US-spec PM2811 supplies to
230 V.
Don't forget to change the fuses (although the supply of course will
work on 230 V with the larger fuses needed for 110 V, just
dangerously). Yes, there are a total of two, same-spec fuses that
need to be swapped... The rating is dependent on the number of
channels (PM2811: 1.25 A, PM 2813: 3 A, slow-blow).
As the original fans in my supplies were audibly lamenting their age,
I also put in new ones: NMB Technologies Corporation
2410SB-05W-B20-B00 24 V fans (one needed for PM2811, three for
PM2813), using Molex 90156-0142 plugs and 90119-2109 crimp inserts to
cable them up.