My 12V field notebook transformer was burnt last time when I tried to capture Mars in a nearby playground, I checked the electronics inside but nothing was wrong apparently, so I didn't throw it away.
After I guess now maybe 5-6 months, I managed to check it again, this time, I found the problem. It's right inside the plug, the fuse was burnt! But I was too quick to cut the wires, so instead of replacing the fuse, now I will make direct connection clips to my 12V Sealed Lead Acid battery, and it will simplify my setup as well.
Actually, there's another fuse in the connection chain, so the one inside the plug is actually no necessary.