LA-E791P works in battery only

[ashiq]

i have a unique issue that when battery is connected it works only in battery no adapter voltage is passed .when no battery it works in ac mode.
when battery connected the ic drive the bat mosfet it will low the ac fet.

i have changed the ic ,mosfet ,programmed io..
any one have faced similar issue pls help!!!

[mcplslg123]

Re: LA-E791P works in battery only

Everyone of us has faced this type of issue but no one can help without any measurements.

[ashiq]

Re: LA-E791P works in battery only

Everyone of us has faced this type of issue but no one can help without any measurements.

is bq24725 and 725a same ???

[mcplslg123]

Re: LA-E791P works in battery only

is bq24725 and 725a same ???

No.

[mon2]

Re: LA-E791P works in battery only

https://cdn.badcaps-static.com/pdfs/...10d99620ae.pdf

[ramzi2019]

Re: LA-E791P works in battery only

Hi everyone,
I'm facing the same problem.

The motherboard model is:
CSL50/CSL52 LA-E791P
REV:2.0
2017-07-18

I joined an image to the post with taken measurements ( The multimeter that I use is not perfect so excuse me for any mistake ).


I'm using the schematic from this post
https://www.badcaps.net/forum/attach...3&d=1634195060

[mon2]

Re: LA-E791P works in battery only

ACDET voltage is too low. Are you using the official power adapter? Rated with enough power for this model?

Review the datasheet for the charger ic and the details needed for the ACDET pin.

[ramzi2019]

Re: LA-E791P works in battery only

ACDET voltage is too low. Are you using the official power adapter? Rated with enough power for this model?

Review the datasheet for the charger ic and the details needed for the ACDET pin.

Thanks for help.

According to datasheet

• 0: AC Adapter is not present (ACDET < 2.4V) <default @ POR>
• 1: AC Adapter is present (ACDET > 2.4V), no deglitch time, read only

I attached two images for the power adapter that I use.

Can the two resistors R1 430k and R2 66.5k be the problem and need to be replaced ?

[mon2]

Re: LA-E791P works in battery only

Remove all power. Meter in resistance mode. Carefully measure the resistance of these 2 resistors. Post the measurements.

[ramzi2019]

Re: LA-E791P works in battery only

Remove all power. Meter in resistance mode. Carefully measure the resistance of these 2 resistors. Post the measurements.

Thanks for your time.

I attached an image with the suspected resistors and measurements.

I think the R1 430k resistor need to be replaced???

[mon2]

Re: LA-E791P works in battery only

Can you post a pic of your meter setting for these resistance checks?

[ramzi2019]

Re: LA-E791P works in battery only

Can you post a pic of your meter setting for these resistance checks?

This is a picture of my settings.

[mon2]

Re: LA-E791P works in battery only

Use the 2M meter scale for R1 checking.

Use the 200k meter scale for the R2 66.5k checking.

Post the measurements again. It is possible that these parts are reporting a bad reading as they are soldered onboard but for the very low cost of resistors, suggest to replace both of them.

The resistors should be 1% tolerance and the same physical size as the original. Will check against the schematic and offer suggestions.

Do you have a local supplier for surface mount parts? Or you can buy through Digikey / Mouser or Aliexpress? Suggest Digikey if possible - perhaps RS Electronics in Europe.

The parts are 0402 in SMD size and 1% tolerance.

Be sure to purchase the same values as shown in the attached schematic. Purchase spares as they are easy to lose even with good motor skills and tweezers.

You must place the proper resistor value in the proper smd pad for this circuit to function. The higher resistor value is the one that mates with the +19 volts. Confirm this detail now before removing the old parts. Carefully check the voltage on the tips of the present resistors to confirm the +19v reaches the 'R1' resistor.

[ramzi2019]

Re: LA-E791P works in battery only

Use the 2M meter scale for R1 checking.

Use the 200k meter scale for the R2 66.5k checking.

Post the measurements again. It is possible that these parts are reporting a bad reading as they are soldered onboard but for the very low cost of resistors, suggest to replace both of them.

The resistors should be 1% tolerance and the same physical size as the original. Will check against the schematic and offer suggestions.

Do you have a local supplier for surface mount parts? Or you can buy through Digikey / Mouser or Aliexpress? Suggest Digikey if possible - perhaps RS Electronics in Europe.

The parts are 0402 in SMD size and 1% tolerance.

Be sure to purchase the same values as shown in the attached schematic. Purchase spares as they are easy to lose even with good motor skills and tweezers.

You must place the proper resistor value in the proper smd pad for this circuit to function. The higher resistor value is the one that mates with the +19 volts. Confirm this detail now before removing the old parts. Carefully check the voltage on the tips of the present resistors to confirm the +19v reaches the 'R1' resistor.

Thanks a lot for your help.

Because of multiple attempts to get a good measurement of R1, I destroyed it.
In any case, I will try to get another similar one from old motherboards because there are no nearby suppliers and purchasing from the internet is very complicated in my country.

I will inform you of the results as soon as possible.

Thank you so much

[mon2]

Re: LA-E791P works in battery only

Ok. NP. From my little knowledge, I think our olive oil is sourced from your region. Very tasty.

These 2 resistors are not critical in their values but should be 0402 in size so you can solder them in place.

These 2 parts are building a resistor based voltage divider. So the values can vary but you must use a calculator to understand the target voltage.

See here:

https://www.digikey.ca/en/resources/...oltage-divider

Use 19 volts as the Vin and then apply the resistor values that you own or find on the donor boards.

The trick is to exceed the ACDET trigger voltage (ie. 2v7). So in the end, the R1 and R2 values can vary but the goal is to meet and exceed the threshold value.

Do post back before proceeding if there is any doubt.

[ramzi2019]

Re: LA-E791P works in battery only

Ok. NP. From my little knowledge, I think our olive oil is sourced from your region. Very tasty.

These 2 resistors are not critical in their values but should be 0402 in size so you can solder them in place.

These 2 parts are building a resistor based voltage divider. So the values can vary but you must use a calculator to understand the target voltage.

See here:

https://www.digikey.ca/en/resources/...oltage-divider

Use 19 volts as the Vin and then apply the resistor values that you own or find on the donor boards.

The trick is to exceed the ACDET trigger voltage (ie. 2v7). So in the end, the R1 and R2 values can vary but the goal is to meet and exceed the threshold value.

Do post back before proceeding if there is any doubt.

Thank you for the addition on olive oil, this year the prices have been too inflated for ordinary citizens and the quality is unknown.
Let's hope that a quantity of the good product can reach good people like you.
In any case, for the repair of the motherboard, I will follow your instructions and I will inform you of the results.

Thank you for your time and kindness