Just spent an hour or so slowly fiddling away with a Dell 1850 PSU, retrofitting voltage regulation to it. With a 10K linear pot (it says "RFT" but I somehow have a hard time believing it's from DDR) the regulation is strongly non-linear; one gets a lot of travel regulating easily on mV steps, and then all of a sudden it jumps up above 13,9V and then further on straight into protection.. Probably should give a log pot a try. Found out that one of my radios, an Ericsson / Niros 70cm mobile, is very picky with its "12V" and wants the battery version of that, ie. 12,6 or so minimum..