Michelle here, also have a 71 25' Land Yacht. My converter charger was shot
so I replaced it with an ordinary
battery charger and so far so good. Re your battery not staying charged,
have you checked to make sure the battery
is good, fluid level is full? A next step could be to find out what is
draining the battery by disconnecting everything
and reconnecting things one at a time. The fuse panel is a good way to
disconnect things. Find out if the battery
will hold a charge with nothing hooked up. You need a VOM (volt ohm) meter
to troubleshoot the electrical.
imho,
best,
Michelle