Author Topic: LG E400 no boot, totally dead  (Read 816 times)

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Offline panoss

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LG E400 no boot, totally dead
« on: August 20, 2018, 02:09:54 pm »
I have an LG E400.
It does not boot, it doesn't do anything, dos not react to anything.
I press the on switch, nothing. I plug in the usb charger, nothing.
Battery is charged.
The on-off switch works fine.
Visibly, no part looks burnt.
Any hint is welcome (or service manual of E400 or similar model).
« Last Edit: August 20, 2018, 02:23:10 pm by panoss »
 

Offline panoss

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Re: LG E400 no boot, totally dead
« Reply #1 on: October 30, 2018, 08:19:25 am »
Ok, back to this old LG phone (I know it 's an old practically useless phone but my goal is self 'educational').

I 've found the service manual.
You can get it from here: https://www.manualslib.com/manual/1227017/Lg-Lg-E400.html
Click the 'Download' green button on top left. Then tick the box in the Captcha 'I 'm not a robot' and answer on the related question that proves you 're human.
And then click on 'Download PDF'.


When I connect it to USB power supply it draws 340mA.
This is with the battery in the phone. I suppose it's charging the battery.
Battery voltage is at 3.8V.
When I press the power on button, nothing happens: does not vibrate, no light, nothing. And the current draw remains unchanged at 340mA.

I used the service manual:

Service manual, page 92, 4.10 Power on Trouble Shooting: Voltages at test points are correct (these voltages appear after pressing the power on button):
VREG_MSMC1_1.1V (L400),
VREG_MSMC2_1.1V (L401)
vREG_MSME_1.8V (L402),
vREG_P3_2.85V (c453),
VREG_MSMA1_2.6V (C448),
VREG_MSMA2_1.2V (C444),
VREG_TCXO_2.85V (C449)

Next step is to check the clock but I cannot, I have no oscilloscope.
Service manual, page 144: According to the block schematic:
vibrator is connected to PM8029 IC (Power Manager chip). And gets activated by this. So, the fact that it does not vibrate at all, means the PM8029 is faulty?

So, my question is: is there some way to check PM8029 so that I 'll be sure 100% if it works or not?
« Last Edit: October 30, 2018, 08:23:57 am by panoss »
 

Offline t1d

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Re: LG E400 no boot, totally dead
« Reply #2 on: October 31, 2018, 09:38:51 am »
Don't forget to check YouTube, for your make and model and general problem. They have rather decent repair videos.
 

Offline panoss

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Re: LG E400 no boot, totally dead
« Reply #3 on: October 31, 2018, 10:44:24 am »
I watched a few but none of them helped.
Thanks anyway!
 


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