Base video setting on MicroHD is 480i 60Hz normally as default, I believe. At least on the small plug-in video cord. You might want to try that if you still have the cord.
Try this: Hit 'Menu', then "down arrow" twice (this might vary depending where you last were in the menu), then "right arrow"once, then 'List-OK" then 'Right arrow' and see what happens... Each "right arrow' press changes to another resolution, provided you actually are on the Resolution screen. Once you get it where you want it, hit 'Exit' 3 times in a row.
As Primestar31 correctly stated, the AV RCA output is always 480i / 60hz. If there is no video on the AV you might try walking through a blind factory reset or restore firmware via the TTL serial port.