MobileRead Forums - View Single Post - Undemo/Unbrick PW1 3G: Can't write to flash?

JackPack · 03-07-2015, 06:54 PM

As a followup to my previous post, I can confirm that these symptoms are a case of bad flash. This looks to be the same situation as the 'read-only' problem described in https://www.mobileread.com/forums/sho...d.php?t=256723

I had a third unit on which I successfully disabled demo mode, and there are some differences in behavior that are definite clues that the flash does not store data and is bad.

1) Apparent inability to update data in the partitions. kernels, system, diag images, user files revert after an update. E.g. write a file to /mnt/us in USB mode. Reboot. The file will be gone.
2) Using idme, changed nvram values do not stick. E.g. 'idme bootmode diags' followed by idme will still show bootmode main and the unit will boot into main instead of diags on next startup
3) When writing files to the unit, either in USB mode or via fastboot, the write speed will be too high. i.e. the copy will finish too quickly. If operating correctly, it should be around 3MB/s - if bad, may be 3x that.

I sacrificed the unit that was in the boot loop and removed the shields on the PCB. I attempted to reflow the BGA memory chips, but it didn't help. If you have the skills, the chip is a Samsung KLM2G1HE3F-B001 153 FBGA. It's under the longer rectangular shield.

Hope this helps someone else in the future.

Jack

03-07-2015, 06:54 PM	#2
JackPack Junior Member Posts: 3 Karma: 10 Join Date: Mar 2015 Device: Kindle PWG	As a followup to my previous post, I can confirm that these symptoms are a case of bad flash. This looks to be the same situation as the 'read-only' problem described in https://www.mobileread.com/forums/sho...d.php?t=256723 I had a third unit on which I successfully disabled demo mode, and there are some differences in behavior that are definite clues that the flash does not store data and is bad. 1) Apparent inability to update data in the partitions. kernels, system, diag images, user files revert after an update. E.g. write a file to /mnt/us in USB mode. Reboot. The file will be gone. 2) Using idme, changed nvram values do not stick. E.g. 'idme bootmode diags' followed by idme will still show bootmode main and the unit will boot into main instead of diags on next startup 3) When writing files to the unit, either in USB mode or via fastboot, the write speed will be too high. i.e. the copy will finish too quickly. If operating correctly, it should be around 3MB/s - if bad, may be 3x that. I sacrificed the unit that was in the boot loop and removed the shields on the PCB. I attempted to reflow the BGA memory chips, but it didn't help. If you have the skills, the chip is a Samsung KLM2G1HE3F-B001 153 FBGA. It's under the longer rectangular shield. Hope this helps someone else in the future. Jack