Can I use maaser money to pay to get my teffilin checked and get new straps?
The general rule is that we may not use maser money for mitzvos that we are obligated to do, and according to most poskim, this also applies to things that are hidur mitzvah. Therefore it should not be done from maser money. However, if you are a poor person, then you don’t have to give maser, and if you took maser you may use it for your mitzvos.
Levush Y:D 149-1, Mayshiv Davar 2-75, Maharam Shik Y:D 130, Borach Tzedakah 11- 5,6.