Troubleshooting Kindle PW5 Gen 11 wont turn on (Help!)

[symondo]

Hi All, Posting here in the hope of rescuing a kindle Paperwhite 5 gen 11.

I brought the near new kindle with the following fault:

Battery symbol screen with exclamation mark.
Previous owner tried charging for a few days to no avail.

My Testing and observations:

The Kindle unplugged gives no sign of life. But if you plug it into USB charger / Laptop the amber charge light comes on, Stays on for approx 30min then turns off. If you try holding the power button on (while connected to power) the led turns green, Then flashes twice green, Followed by 5 x amber flashes. If you continue to hold the power button it will cycle through the same with a short flash of the screen back lighting in between.

I assumed from the beginning a battery issue. Dissasembled and disconnected the battery. no voltage was measurable on the terminals so I suspected battery protection ic had isolated the battery from over discharge.

I applied a gradual charge voltage and slowly recovered the battery over a couple of days. Eventially reaching a teminal voltage of 4.2v. I applied a load of 170mv accross teminals (Test light bulb) which the battery appeared ok with.

I reconected the battery and tried to perform a 40+ sec reset. there is no response to the power button. However if I do the same with usb power connected I get the 3 green / 5 amber flashes repeating. It is like the kindle refuses or does not see the battery. I tried the same with battery disconnected with usb power. No response. So the battery is being used in circuit to some degree.

Battery is a ST32 58-000426 Sunwoda Electronic Co. Ltd
Connections: P-, NTC, ID, P+ plus two NC termonals (not connected)

My next reluctant step is to remove some sheilding (Hot Air station) to measure components underneath.

Ever hopeful someone here may shed some light on what else to do or if you are experiencing the same?

Any input welcome.

[shamanNS]

Originally Posted by symondo

My next reluctant step is to remove some sheilding (Hot Air station) to measure components underneath.

You plan to search for UART / serial port contact points?

[symondo]

Originally Posted by shamanNS

You plan to search for UART / serial port contact points?

No i have not reasearched that possibility yet. I see someone on another thread posted pictures with sheilds removed. Hopfully they don't mind me repeating them here.

Images deleted.

Many rear contact ponts. I will look into it. Any advice on that route also appreaciated.

[symondo]

I have read from this kindle repair site common problems with a shunt resistor.

http://ebookrepairs.com/uncategorize...-not-charging/

I see it here for the PW5 (Red Arrow): I will have to remove sheild & reflow solder on that resistor. Worth a try. I also have ordered a USB to serial adapter capable of 1.8v. this looks to be a fun (ish) learning curve. Any input from experience welcome.

Image deleted.

[symondo]

More discoveries in this process. I removed the sheilding And reflowed the solder on the shunt resistor. (Ugly soldering i know.) Tried turning on but has the same origonal symptoms. Shunt has good continuity. Battery neg is common with usb sheild. Measuring from neg to shunt. 0.106Volts. ??
I decided to put a ammeter & voltmeter in series with the battery via jumper leads. 4.2 volts isolated. On feeding to the battery connector it drops to 0.106 volts.
I tried some external load and the battery still holds good.

This is what i discovered. I have a momentary high current when connected to the kindle spiking above 3 amps when i feed through the battery connector. The battery protection IC shuts off leaving me with 0.106 volts. resets back to 4.2 volts when disconnected. There is a shorted component somewhere.

Image deleted.

I will search more but please share if anyone else has experience this and knows where to look.

[symondo]

Its Alive! but in a weird way. I was searching for shorted PCB components. First stop diodes. All ok. I started doing voltage drop testing by momentarily connecting the battery & probing different sites on the pcb. A quick spike in voltage then dropping to around 0.106 volts at the shunt.

But here is the weird kicker.... I was probing at the shunt while cycling the battery & suddenly the the voltage shot up & stayed @ 4.2volts. ???

But I didn't do anything in reality? My only theory is maybe the battery protection IC is to sensitive & cannot handle capacitor inrush of a completely dead kindle?? I dont know.

With that I pressed the power button & it powered up for the first time.
It charged untill green & now acts like a normal alive kindle.

Weird.

All I can say from this experience is there may be a fundimental flaw in the battery protection ic vs kindle battery managment. Don't know. At least this thread may offer some diagnostic assistance to someone experiencing the same...



Would love to hear of anyone has experienced something similar.