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TheBard · 02-07-2010, 02:35 PM

My JBL froze last night, but I may have found a possible solution.

History:
JBL with rechargeable batteries. Battery indicator showed 4 bars ("full") for a couple of days, then dropped to 3 bars.
Reading an ebook last night, and battery indicator changed from 3 bars to 2 bars (half empty/full)
A minute or two later, the screen blanked. The low battery warning was NOT visible at any time.

Early attempts to fix:
1. Tried turning JBL ON with same batteries. No luck.
Replaced batteries with a set of Alkalines, and tried turning ON. No luck.

2. Depressed and released RESET button, and tried turning ON again. No luck.
Held down ON button for several seconds. Jetbook 1st screen appeared, and LED illuminated (steadily). JBL did not boot after several minutes. (This seems to be the appearance seen by previous posters)

3. Temporarily removed batteries, and reinserted same Alkalines. Depressed & released RESET button. Held down Right Arrow button and ON button. Message appeared that firmware was not able to be updated.

3. Removed SD card, inserted SD card with firmware, repeated firmware load sequence (step 2, above). LED went ON, and blinked intermittently. After a fairly short time (minute or two), JBL rebooted and showed the normal three choices! Success!

4. Replaced firmware SD card with card containing books, replaced Alkalines with freshly-charged rechargeable. Turned JBL ON. "Books" graphic eventually appeared, and after a while, the normal three choice screen appeared. Success again! My bookmarks were preserved as well!

Hypothesis:
The discharge curve of NiMH rechargeables is different than that of Alkalines. Also, NiMH provide 1.2 volts per cell, rather than the 1.5 volts provided by Alkalines. This may have "confused" the battery meter, and allowed the JBL to shut down because of insufficient power.

Will keep checking, and see if it happens again at the 1/2 charge point.

Conclusion:
The "reinstall firmware fix" worked, at least in this case. In some cases it might take a fairly long time to reinstall the firmware, and the Jetbook first page may be the only thing on the screen. You might take note of LED activity. If it blinks occasionally, the SD card with firmware IS being read.

02-07-2010, 02:35 PM	#45
TheBard Bifocal Wearer Posts: 49 Karma: 38902 Join Date: Jan 2010 Location: USA Device: Kobo Touch, Aura, Clara ...	My JBL froze last night, but I may have found a possible solution. History: JBL with rechargeable batteries. Battery indicator showed 4 bars ("full") for a couple of days, then dropped to 3 bars. Reading an ebook last night, and battery indicator changed from 3 bars to 2 bars (half empty/full) A minute or two later, the screen blanked. The low battery warning was NOT visible at any time. Early attempts to fix: 1. Tried turning JBL ON with same batteries. No luck. Replaced batteries with a set of Alkalines, and tried turning ON. No luck. 2. Depressed and released RESET button, and tried turning ON again. No luck. Held down ON button for several seconds. Jetbook 1st screen appeared, and LED illuminated (steadily). JBL did not boot after several minutes. (This seems to be the appearance seen by previous posters) 3. Temporarily removed batteries, and reinserted same Alkalines. Depressed & released RESET button. Held down Right Arrow button and ON button. Message appeared that firmware was not able to be updated. 3. Removed SD card, inserted SD card with firmware, repeated firmware load sequence (step 2, above). LED went ON, and blinked intermittently. After a fairly short time (minute or two), JBL rebooted and showed the normal three choices! Success! 4. Replaced firmware SD card with card containing books, replaced Alkalines with freshly-charged rechargeable. Turned JBL ON. "Books" graphic eventually appeared, and after a while, the normal three choice screen appeared. Success again! My bookmarks were preserved as well! Hypothesis: The discharge curve of NiMH rechargeables is different than that of Alkalines. Also, NiMH provide 1.2 volts per cell, rather than the 1.5 volts provided by Alkalines. This may have "confused" the battery meter, and allowed the JBL to shut down because of insufficient power. Will keep checking, and see if it happens again at the 1/2 charge point. Conclusion: The "reinstall firmware fix" worked, at least in this case. In some cases it might take a fairly long time to reinstall the firmware, and the Jetbook first page may be the only thing on the screen. You might take note of LED activity. If it blinks occasionally, the SD card with firmware IS being read.