Last week I encountered a ZMax receiver that took forever to read the SD Card. And after it completed registering the card (about 10 minutes), the ZMax just rebooted. I watched it happen.
I pulled the SD Card and stuck it in my laptop to check out the Micro_Z.bin.
Of course the file was 512 megabytes in size.
This won’t work! There is not enough internal memory in a ZMax to mount a Micro_Z file larger than 128 meg and I STRONGLY recommend that you use a 24-Meg file.
If you find yourself in the position, you can quickly fix it by
1. Download this ZIP file: http://www.ashgps.com/bin/MICRO_Z.zip
2. Unzip the contents to a ‘MICRO_Z.bin’ file.
3. Format the SD card.
4. Just copy the extracted ‘MICRO_Z.bin’ file to the SD card.
The smaller bin file will mount very quickly.
My theory is when the file is damaged, the ZMax builds a new one that completely fills the available SD card. And 512 Meg is just way too big.
BTW, I don’t think that the ZMax can read SD cards larger than 2 gig.
M
iG GPS 
Hi, I noticed you hace a zmax unit. Have you ever encountered the problem of the unit reformatting the SD card after logging a 2nd station? The unit won’t save more than 1 station on 1 SD card. I suspect that it has something to do with the internal battery because the date of the micro z.bin file is always year 2000. I have been trying to get a manual for the replacement of the internal battery. Let me know if you have any idea about this problem Thank you.
Hi Gerry!
Not exactly, however I suspect that you have a large SD card. Large SD cards are okay, but I don’t think that there is enough internal memory in the ZMax, or enough horsepower, to process the resulting raw directory entries for the card.
I believe it is Okay to use a larger card (perhaps 2 or 4 GB as an upper end); however you want to format the card, in your computer using Windows or Linux, and then copy a smaller format file (the micro-Z file) a described above.