Samsung A40 took a little swim... but signs of life! Any ideas?

[DannySolo]

Hi all. My trusty A40 had a little mishap at the toilet (!) and drowned. I gave it a rinse with alcohol and dried it for days in 40C ovens etc. but no life was recovered. A few days ago I decided to try charging it anyway and nothing happened... then this morning my old alarm went off! The screen is still completely dead, and I didn't notice any vibration but I always had that turned off. When I plug it in and out with the USB cable it makes the correct beeps. I can even snooze that alarm with the power button and turn it off with volume down.
When I connect it to my PC though I don't see any drive come up, I guess it doesn't default to USB file transfer so maybe this isn't a surprise.
So is my phone alive inside and just has a completely dead screen? The alcohol has conveniently taken the back off by dissolving the glue. Also, I've already got a new Redmi Note 11 so I'm happy to tinker with this phone and I've replaced screens before no problem.
Is this phone worth buying a new screen for do you all think or would that be a total waster of $35?
Thanks!
(PS: sorry if not in correct forum here, not sure which one is most appropriate for hardware / repair issues)

 

[blackhawk]

Wrong. You may still be able to save it...
Pull the back cover and disconnect the battery asap. Allow to dry completely before powering up. Fan blowing on it with the phone on it's side in a very warm room for at least a couple days.
The mobo power section or the soc are the most likely areas to fail from corrosion. Possible the connectors are still retaining brown water

Do Not use anhydrous isopropyl alcohol as a drying agent if it has an LCD as it will poison it.

 

[DannySolo]

Wrong. You may still be able to save it...
Pull the back cover and disconnect the battery asap. Allow to dry completely before powering up. Fan blowing on it with the phone on it's side in a very warm room for at least a couple days.
The mobo power section or the soc are the most likely areas to fail from corrosion. Possible the connectors are still retaining brown water

Do Not use anhydrous isopropyl alcohol as a drying agent if it has an LCD as it will poison it.

Thanks but I've already completed the drying. The CPU is working in there, in fact when I put in a SIM it will even ring when I phone it. I'm just wondering if I can be 100% sure everything is OK apart from the screen? Is there anything else I can check?

 

[blackhawk]

Thanks but I've already completed the drying. The CPU is working in there, in fact when I put in a SIM it will even ring when I phone it. I'm just wondering if I can be 100% sure everything is OK apart from the screen? Is there anything else I can check?

If it's dry and still malfunctioning the damage is likely to the mobo, is permanent and will be progressive. Corrosion never sleeps.
You can disassemble and check the ribbon cable pins going to the display for moisture and/or corrosion damage. The mobo power section and the BGA chipsets* (can't see the damage as the contacts are under the chip) are the most likely to be damaged.

With water exposure time is of the essence. You might save the device if you're fast enough and do the right things. Salt water is sure death.


* you sure it's dry?!! BGA chipset's don't have airflow around the pins. Any water under the chipset will also be retained by capillary action...

 

[DannySolo]

If it's dry and still malfunctioning the damage is likely to the mobo, is permanent and will be progressive. Corrosion never sleeps.
You can disassemble and check the ribbon cable pins going to the display for moisture and/or corrosion damage. The mobo power section and the BGA chipsets* (can't see the damage as the contacts are under the chip) are the most likely to be damaged.

With water exposure time is of the essence. You might save the device if you're fast enough and do the right things. Salt water is sure death.


* you sure it's dry?!! BGA chipset's don't have airflow around the pins. Any water under the chipset will also be retained by capillary action...

I submerged the whole thing in alcohol and then dried it at 50C for 72 hours. Everything I can test works perfectly (including ringing when called) but the screen is totally dead. I cleaned that socket but still nothing.
Is it possible the water/alcohol damaged the screen and not the motherboard? Sound unlikely but that's what they symptoms indicate.
So is it worth a bet on fixing with a $30 new screen or not do you think?

 

[blackhawk]

I submerged the whole thing in alcohol and then dried it at 50C for 72 hours. Everything I can test works perfectly (including ringing when called) but the screen is totally dead. I cleaned that socket but still nothing.
Is it possible the water/alcohol damaged the screen and not the motherboard? Sound unlikely but that's what they symptoms indicate.
So is it worth a bet on fixing with a $30 new screen or not do you think?

I think it's the mobo but you're holding it. I don't know how suspectable the the display is to water damage. Did you use anhydrous isopropyl alcohol?

 

[DannySolo]

I think it's the mobo but you're holding it. I don't know how suspectable the the display is to water damage. Did you use anhydrous isopropyl alcohol?

All I could find was 100% ethanol I'm afraid and only realised the FAQs saying "alcohol" were talking about isopropanol after I'd finished. Isn't ethanol also used for mobo cleaning? Maybe that destroyed the screen though.

 

[blackhawk]

All I could find was 100% ethanol I'm afraid and only realised the FAQs saying "alcohol" were talking about isopropanol after I'd finished. Isn't ethanol also used for mobo cleaning? Maybe that destroyed the screen though.

Water can damage AMOLED displays as well it seems. Best to keep all solvents away from the display. Methanol alcohol should never be used.
Ethanol not sure about.

 

[DannySolo]

Water can damage AMOLED displays as well it seems. Best to keep all solvents away from the display. Methanol alcohol should never be used.
Ethanol not sure about.

OK I think then I'll shoot the moon and buy a replacement screen... would be a terrible waste to throw this phone out if that's all that's wrong.
Plus we would now know that ethanol is OK for phone motherboards, plus it takes the glue off the back of a Samsung A40!

 

[blackhawk]

OK I think then I'll shoot the moon and buy a replacement screen... would be a terrible waste to throw this phone out if that's all that's wrong.
Plus we would now know that ethanol is OK for phone motherboards, plus it takes the glue off the back of a Samsung A40!

Use anhydrous (preferably 96% minimum 93%) isopropyl alcohol.
I wouldn't go too nuts trying to save it due the price point and especially the fact it has known water damage. Buying a used one in good condition be a viable option if you really like that model.

 

[DannySolo]

Use anhydrous (preferably 96% minimum 93%) isopropyl alcohol.
I wouldn't go too nuts trying to save it due the price point and especially the fact it has known water damage. Buying a used one in good condition be a viable option if you really like that model.

I've just notices that with this model there is a pretty hefty flex between the top and bottoms boards with a connector on each end. This must also carry screen data so I'll give that a good clean out.
Second hand AMOLEDs are impossible to find for the A40, they all have horrible burn in.
I'm going to get the INCELL LCD version already in a new front frame and go from there. Should still be a decent back up phone.
And the fun of fixing it is what it's all about anyway, right? :-D

 

[blackhawk]

You grossly underestimate the corrosion process that's likely been initiated. I'm not so optimistic about it ever being reliable again.

 

[DannySolo]

I can understand corrosion while the phone is wet... not after it's been soaked in alcohol and completely dried. The process doesn't continue.
I'm going to guess it's the screen only that's broken as I see no other issues... I bought a cheap LCD replacement already in a new frame for $30.
Let's see how it goes.

 

[blackhawk]

I can understand corrosion while the phone is wet... not after it's been soaked in alcohol and completely dried. The process doesn't continue.
I'm going to guess it's the screen only that's broken as I see no other issues... I bought a cheap LCD replacement already in a new frame for $30.
Let's see how it goes.

Yes, yes it does. Most don't understand how insidious it is. The oxides formed are insoluble in water and alcohols. Many are hygroscopic and attract moisture, then you know what happens...
This is the same reason you never buy a flood damaged car. Even if everything is working it will start to fail sure as the sun rises in the morning.
Sometimes if you pull the battery before the flooding it can be saved... sometimes. Always check for signs of water damage when buying a vehicle. EV's just burn to the ground when water damaged

Energized circuits greatly exacerbate and accelerate the corrosion process. You see the results. The future is uncertain for that phone but it will likely eventually fail from that one prolonged exposure.

 

[Mikicrep]

I can understand corrosion while the phone is wet... not after it's been soaked in alcohol and completely dried. The process doesn't continue.
I'm going to guess it's the screen only that's broken as I see no other issues... I bought a cheap LCD replacement already in a new frame for $30.
Let's see how it goes.

tell results

 

[DannySolo]

OK so the new screen eventually arrived and I turned on the phone then plugged in the new screen... nothing. But I guess you have to plug in the screen and then turn it on, but that seems to be impossible with the A40 where you need to attach the middle frame for to use power/volume, and that blocks the screen connector.
Is there some way to bridge those little spring contacts on the PCB to reproduce a power on signal? Otherwise I'll just have to do the whole replacement process and see what happens at the end!
Just as well there's holidays coming.

 

[Mikicrep]

OK so the new screen eventually arrived and I turned on the phone then plugged in the new screen... nothing. But I guess you have to plug in the screen and then turn it on, but that seems to be impossible with the A40 where you need to attach the middle frame for to use power/volume, and that blocks the screen connector.
Is there some way to bridge those little spring contacts on the PCB to reproduce a power on signal? Otherwise I'll just have to do the whole replacement process and see what happens at the end!
Just as well there's holidays coming.

i do not know, sorry, never opened my a40, still using it right now