I think the O.P. might be talking about an invertor (dc in ac out).
"Tim" wrote in message
...
In article ,
says...

"postielady" wrote in message
ups.com...
Hi
Can anyone give me some advice on my caravan transformer, the
transformer buzzes but no power comes out.

Could be a bad connection or an open secondary (unusual). If it buzzes,
the
primary is energized.



Are you talking about the actual transformer, or a power supply? People
often call a power supply (AC in DC out) a transformer, but techs are
talking the actual AC to AC part inside that drops the voltage down to
12 or so.

Just getting the full info....

- Tim -