I purchased a GLXD16. When I press the pedal to go to tuner mode, it goes "dead" for a bit and typically takes about 10-15 seconds to be operational. Likewise, when I press the pedal to go back to wireless mode, it takes awhile to be operational again. Is this normal?
No. The change to the Tuner Mode and back out this Mode should be relatively quick - less than 2 seconds.
If the GLXD6 does not respond as described above, contact Shure Service to have the unit examined/tested/repaired. In the United States, call 800-516-2525.