sudo hdparm -r0 /dev/sdb1

/dev/sdb1:
 setting readonly to 0 (off)
 readonly      =  0 (off)
-----------------------------
 sudo fsck -n /dev/sdb1
fsck from util-linux 2.20.1
fsck.fat 3.0.26 (2014-03-07)
0x41: Dirty bit is set. Fs was not properly unmounted and some data may be corrupt.
 Automatically removing dirty bit.
FATs differ but appear to be intact. Using first FAT.
/PVR/TEMPTEST.SPD
  File size is 1 bytes, cluster chain length is > 4096 bytes.
  Truncating file to 0 bytes.
Free cluster summary wrong (764153 vs. really 764154)
  Auto-correcting.
Leaving filesystem unchanged.
/dev/sdb1: 5 files, 180333/944487 clusters