The DMSCalculator is useful to convert decimal degree value to degrees, minutes and seconds. But there may be cases where the slight computational error causes a trouble.
2014-10-03: I had discussed about the computational error in the DMSCaluculator (Version 0) with Safe's developer, then the new DMSCaluclator (Version 1) has become available in FME 2015 Beta build 15187. It's better on handling the computational error than the previous version, you will not need to consider the following workaround, in FME 2015.
Although computational error cannot be avoided, there are ways to reduce it in some cases.
In the DMS calculation, I prefer to define math expressions myself, rather than using the DMSCalculator, so that the computational error can be reduced.
2014-09-24: Sorry, I didn't take care of negative source values - i.e. south/west hemisphere latitude/longitude. I'm living in north/east hemisphere of the earth.
Try these expressions for calculating minutes and seconds, if the source may be negative.
When the source is negative, a minus sign will be added to degrees value only.
(FME 2014 SP3 build 14391)