Is my phone's charging system working?

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Samsung Galaxy A40

The Samsung Galaxy A40 was released in April 2019.

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TheElectronicsFixer @theelectro54594

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投稿日: 2024年6月29日

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Is my phone's charging system working?

Hi, so I dropped my samsung phone into the sea in winter and I left it on my drawer for months. Now I tried to fix it, took off the motherboard shields and cleaned the corrosion. After that I replaced the charging board. Now I measured the end of the main flex and it shows 5v. When I measure the battery connector it shows 2.1volts. Is this normal? Should I pay 70 dollars to replace the screen and battery or is it a waste? Please answer, it is a very important phone to me, thank you

@oldturkey03 I cleaned all corrosion tho, even under the sheilds... Could it indicate anything else? Also now that I am checking with my multimeter I check 2.4 volts at the battery connector while charging instead of 2.1 volts. Also heres a photo of the motherboard

Also I got the ammeter, it shows 5volts and 0.00 amps. What should I do? My new battery also reads 2.65 volts with the multimeter, is it normal?

@oldturkey03 here you go:

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@theelectro54594 what does the underside of the board look like?

Perfect. Thank you. Looks like you have some trouble with the EMI shields. Hard to see even when zoomed in but you do not see any damaged traces? (last picture bottom right)

oldturkey03 さんによる2024年7月5日

@oldturkey03 I don't think they are damaged... I tries to pry them up with a screwdriver and without any heat, big mistake. But why does my ammeter show 0.00 amps? Why is my new battery 2.65 volts? Is it bad? What is the chip responsible for power management and charging and how do I check them?

TheElectronicsFixer さんによる2024年7月5日

@theelectro54594 that means your phone is not pulling any amps from your charger. which is bad. That means you are having a shorted charging circuit. Let me see if I find the PMIC for the charging logic

oldturkey03 さんによる2024年7月5日

@oldturkey03 So.... are there any news? What should I do about the 0.00 amps? Should I replace my new battery again which is 2.65 volts? I need some further instructions. Thank you

TheElectronicsFixer さんによる2024年7月7日

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oldturkey03 @oldturkey03

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投稿日: 2024年6月30日

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@theelectro54594 "When I measure the battery connector it shows 2.1volts. Is this normal?" no, it is not. The 2.1V are below the charging threshold for your battery and will not start your phone or charge the battery. You did not tell us how you cleaned the board, if there was corrosion damage and if you needed to replace any components.

You can also follow the Samsung flowchart and check the components responsible for the power circuit to the battery

Use the Component Layout file and the search function of your PDF reader to locate the components to be checked, on the circuit board.

About the battery replacement etc, you already know the answer since "it is a very important phone to me". Go for it, replace the battery and whatever else and see what happens.

@theelectro54594 The main PMIC is U5002 (for that location, check on the previously attached Component layout file) Check the coils as well as the capacitors related to that with your meter. If nothing else, I would suggest to either try a reflow or replace the IC. It is a S2MPU08A02-6030 BGA IC, so it will require some good tools and skills to repalce. Here is the schematics for it PMIC

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@oldturkey03 I cleaned the mobo with a toothbrush and 95% isopropyl alcohol. Also I put my multimeter in the buzzer mode and tested the positive and negative terminals of the battery connector that shower 1 reading and no beep which I think means there's no shorts right? About the 2.1 volts if I measure 1st from the left pin and the third I get 4.4 volts which I think is normal right? If i test the 1st and last pin I get 2.1 volts. Also the golden grounds on the left side of the charging flex in the main board show 4.4 volts as well. Any idea what I'm doing wrong? Thank you

TheElectronicsFixer さんによる2024年6月30日

@theelectro54594 it should be the outside pins on your battery that are the positive and negative connectors. Do you have a battery connected? Is this a new battery?

oldturkey03 さんによる2024年6月30日

@oldturkey03 The outside pins of the connector show 2.1 volts when charging with no battery. (my old battery is water damaged and doesnt work anymore)

TheElectronicsFixer さんによる2024年6月30日

@theelectro54594 next thing to do would be to get a new battery. Once you have it installed connect an ammeter between your phone and the charger. Lets see how many amps your phone draws. Your phone should have a usb-c charging port. See if you can find an inexpensive meter that connects in line to it. Don’t Forget to check the motherboard components for corrosion damage. You mentioned seawater that makes me believe that it was saltwater which is pretty corrosive.

oldturkey03 さんによる2024年6月30日

@oldturkey03 you are right, it was salt water.... I believe I cleaned all corrosion but some capacitors are rusted. I checked them with a multimeter on buzzer mode and they seemed to work. Ok I will test this with an ammeter and a new battery and I will tell you

TheElectronicsFixer さんによる2024年7月1日

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@theelectro54594 what does the underside of the board look like?

Perfect. Thank you. Looks like you have some trouble with the EMI shields. Hard to see even when zoomed in but you do not see any damaged traces? (last picture bottom right) — oldturkey03
@oldturkey03 I don't think they are damaged... I tries to pry them up with a screwdriver and without any heat, big mistake. But why does my ammeter show 0.00 amps? Why is my new battery 2.65 volts? Is it bad? What is the chip responsible for power management and charging and how do I check them? — TheElectronicsFixer
@theelectro54594 that means your phone is not pulling any amps from your charger. which is bad. That means you are having a shorted charging circuit. Let me see if I find the PMIC for the charging logic — oldturkey03
@oldturkey03 So.... are there any news? What should I do about the 0.00 amps? Should I replace my new battery again which is 2.65 volts? I need some further instructions. Thank you — TheElectronicsFixer
@oldturkey03 I cleaned the mobo with a toothbrush and 95% isopropyl alcohol. Also I put my multimeter in the buzzer mode and tested the positive and negative terminals of the battery connector that shower 1 reading and no beep which I think means there's no shorts right? About the 2.1 volts if I measure 1st from the left pin and the third I get 4.4 volts which I think is normal right? If i test the 1st and last pin I get 2.1 volts. Also the golden grounds on the left side of the charging flex in the main board show 4.4 volts as well. Any idea what I'm doing wrong? Thank you — TheElectronicsFixer
@theelectro54594 it should be the outside pins on your battery that are the positive and negative connectors. Do you have a battery connected? Is this a new battery? — oldturkey03
@oldturkey03 The outside pins of the connector show 2.1 volts when charging with no battery. (my old battery is water damaged and doesnt work anymore) — TheElectronicsFixer
@theelectro54594 next thing to do would be to get a new battery. Once you have it installed connect an ammeter between your phone and the charger. Lets see how many amps your phone draws. Your phone should have a usb-c charging port. See if you can find an inexpensive meter that connects in line to it. Don’t Forget to check the motherboard components for corrosion damage. You mentioned seawater that makes me believe that it was saltwater which is pretty corrosive. — oldturkey03
@oldturkey03 you are right, it was salt water.... I believe I cleaned all corrosion but some capacitors are rusted. I checked them with a multimeter on buzzer mode and they seemed to work. Ok I will test this with an ammeter and a new battery and I will tell you — TheElectronicsFixer

Samsung Galaxy A40

Is my phone's charging system working?

Update (07/05/24)

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Update 7/7/2024

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