Are you checking your cameras with the TV remote in a darkened room? Remotes don't (usually) give a very strong signal, so any ambient light is likely to hide the effect. This check will need to be made with LiveView, not through the viewfinder, of course
The K-5 will take infra-red pictures through an Ilford SFX, Wratten 89B or R72 filter (very dark red) but will really struggle with a visually opaque filter like a Lee or Wratten 87 … the older CCD sensors are much better in this respect with an unmodified camera.
Expect something in the region of six or seven stops of extra exposure necessary, eg. from 1/750 down to 1/8 @ f/4.5 or thereabouts with an R72 filter, so a good tripod can become a sensible accessory if you don't have a wide aperture lens.
I don't have a K-30 (or a K-1, I wish) so can't comment on those, but an unmodified K-5 will serve perfectly adequately within the parameters mentioned.
Enjoy