its currently running on 12v at 18.5A, but ill see about getting 13.8V
The power supply
is pushing 18.5A when you program it, or
its capable of pushing 18.5a on the 12v rail?
I have made many a bench supply out of old ATX power supplies, and few and far between will push the 12v rail much over 12.2v w/o some resistance...with most hovering at 11.9v. They are not terribly great for radios, and usually crap when you start to TX on them. The RF wreaks havoc on them if you don't have a great radio antenna/grounding setup.
The 13.8v usually referenced comes from a standard alternator charging voltage of 13.8v to 14.2v in a running infernal combustion engine, and radios will usually run just fine on a resting lead acid battery voltage of 12.4v-ish, so you might not find one that is designed to put out 13.8v for a bench supply.
I join the "question the cable" club.