[Radioroslyn]

Ok good. If you are powering them from the AC side of the p/s the heater voltage shouldn't be an issue with the proper cable. The manuals can be found here:  https://bama.edebris.com/manuals/elmac/ 

Plan A. Read the schematic and sort all of the heater/plug connectors.
Plan B. Grab a variac and use that to regulate the ac input to the power supply while watching the heaters.
Plan C. Abandon all cares and plug it in. Flip it on and if you so a bright flash like Hiroshima it's wired wired wrong.

I've had/have the AF-68 & PMR-7. The '68 is a  good little AM transmitter and the 22 1/2 v battery was still good from '60. Sold that one and bought another 4 or 5 yrs ago. Didn't have the p/s so I powered it w/a Harvey-Wells APS-50. Used a hand full of automotive push on connectors to connect to the jones plug.

The PMR-7 I don't remember too well other than it gets hot as a blast furnace and the selectivity is broad as barn door. It's fine for AM but listening to cw or ssb is a challenge.

For those of you that are following at home this is what the AF-68 looks like is the raw. 6146 modulated with a pair of 5881's or 6L6GC's

GLOM