RaspberryPi树莓派无法启动了排查过程

最近没用树莓派，突然无法启动了。RaspberryPi树莓派无法启动了排查过程 记录如下：

1. 首先确认是否电源供电问题。现在的现象是电源灯PWR常亮，电源用的是iPad的。用表接伴奏上的TP1和TP2测了下电压5.05V，看起来电源正常。参考资料为提示：树莓派90%的故障是电源故障！！附5V电源检查方法
2. 又仔细看了下官方的wiki，发现以下一句：“If the card is not new, you should format it and make sure there is only one partition (FAT32 is a good choice); otherwise Win32DiskImager can make corrupt your SD card!” 猜想可能是没写好SD卡。此时把SD卡插到本本的SD卡槽无反应，于是用了个读卡器，这次可以看到SD卡大小为250M，在window磁盘管理里面看到确实有隐藏的分区在SD卡上。于是乎找了恢复工具SD卡擦空还原（恢复原始容量）新工具：SD Formatter恢复后卡容量显示正确。winimagewriter重新烧录2013-02-09-wheezy-raspbian.img。未果，又用flashnul烧了一下，还是只拷贝了60M左右，应该看起来明显不对。
3. 于是换一张新卡，这次拷贝貌似正确，希望这次好用。。。。。。。。。。D:\InstFiles\ISO\Tools\flashnul-1rc1>flashnul.exe I: -L D:/InstFiles/ISO/RPi/Raspbian/2013-02-09-wheezy-raspbian.img
   GetFreeDiskSpaceEx() failed: Access is denied.Disk I: (UNC name: \\.\I:)
   ------------------------------------------------------------[Drive geometry]--
   Cylinders/heads/sectors  = 126130/1/63
   Bytes per sector         = 512
   CHS size                 = 4068449280 (3879 Mb)
   ---------------------------------------------------------------[Device size]--
   Device size              = 4064280576 (3876 Mb)
   delta to near power of 2 = 230686720 (220 Mb), 5%
   -----------------------------------------------[Adapter & Device properties]--
   Bus type                 = (0) UNKNOWN
   Removable device         = Yes
   Command Queue            = Unsupported
   Device vendor            = RICOH
   Device name              = R5C822
   Revision                 = 01
   Device serial            =
   
   --------------------------------------------------------------[Hotplug info]--
   Device hotplug           = Yes
   Media hotplug            = NoSelected operation:      load file content
   Selected drive:          I:, 4064280576b (3876 Mb)THIS OPERATION IS DESTRUCTIVE!!!
   Type 'yes' to confirm operation. All other text will stop it.Really destroy data on drive I:?  :yes-----------------------------------------------------------------------[Log]--
   Runing operation [load file content] for drive I:Writing 0x73960000 (1849 Mb), 6734471 b/s
   image load finished

   ----------------------------------------------------------[Operation result]--
   passes:                 1
   errors:                 0
   write bytes:            1939865600 (1850 Mb)
   avg. write speed:       6734527 (6576 kb/s)
   max/min write speed:    0 (0 b/s) / 0 (0 b/s)

   Press ENTER to exit.

4. 但是上一步的貌似正确的卡还是无法启动。要放弃了的时候又重新拿新卡重复了一遍SDFormater和winimagewriter. 这次尽然启动了...