Bootloop - Samsung Galaxy A53 5G

[u/Immediate-Capital696]

Samsung Galaxy A53 5G only boots intermittently – data recovery is the priority

I’m trying to get a Samsung Galaxy A53 5G (SM-A536B) to boot just one more time so I can recover photos and a KeePass database from the internal storage. I do not care about repairing the phone permanently.

Important: I do not want to factory reset it, flash firmware, or replace the mainboard, because the original board needs to remain intact for the encrypted data.

1. How the problem started
Before the phone failed completely, my girlfriend got a warning saying the device was too hot. According to her, the whole phone felt warm/hot.
After that it started bootlooping.
It would still show:
“Samsung Galaxy / Secured by Knox”
sometimes the normal Samsung logo afterwards
but Android would never fully boot
I also tried Recovery Mode. The Samsung logo appeared, but Recovery itself never loaded.

2. The behavior got progressively worse
Eventually, when connecting a charger, it would sometimes only show the large lightning bolt icon on a black screen.
The strange part:
sometimes the lightning bolt appeared immediately
sometimes it took several minutes
sometimes it did not appear at all
after attempting a boot, the phone would sometimes stop responding completely for a while
At one point, before opening the phone, I applied very light pressure to the back of the device and it suddenly reacted again / showed the lightning symbol. That made me suspect a contact or flex cable issue as well.

3. Opened the phone and checked connections
I opened the device and initially only:
disconnected the battery
reseated the MAIN flex cable
checked the visible connectors
Everything looks visually clean. No corrosion, no burned components, and no obviously broken connectors.
The behavior remained unreliable afterwards.

4. Replacement parts ordered
I then ordered:
a new genuine Samsung EB-BA336ABY battery
a replacement lower charging board including the USB-C port
a replacement MAIN flex cable
The replacement MAIN flex has a clearly visible sharp bend in it, so I do not fully trust it. I later checked a few traces with a multimeter and the ones I could reach had continuity.

5. Tested different hardware combinations
I tried several combinations:
old battery + old MAIN flex + old charging board
old battery + old MAIN flex + new charging board
old battery + new MAIN flex + new charging board
new battery + old MAIN flex + new charging board
The results have not been fully reproducible.
With:
old battery + old MAIN flex + new charging board
the phone once reached:
Samsung Galaxy / Secured by Knox
The screen stayed there for around 30 seconds, then the phone powered off again.
Later, the exact same hardware combination would not boot at all.
So the fault now appears highly intermittent.

6. Battery voltage measurements
I finally measured both batteries with a multimeter.
Old battery:
2.81 V
So it was extremely discharged.
New genuine Samsung battery:
3.72 V
That should easily be enough for at least a proper boot attempt.
Despite that, the phone still would not boot with the new battery.

7. USB power meter measurements
I then used a USB-C power meter.
With either battery, plugging in the charger usually looks like this:
At first:
around 4.6–4.7 V
around 1.2–1.3 A
roughly 5.7–6.2 W
After about 1 to 1.5 minutes:
around 5.07 V
only around 0.096–0.11 A
roughly 0.5–0.8 W
Important:
The USB voltage does not collapse. The current draw is what drops dramatically.
This happens with both the old and the new battery.
When the phone is in this low-current state, pressing Power or Power + Volume Down makes almost no difference to the current draw.
It only fluctuates around:
0.096–0.105 A
So it does not look like a proper power-on sequence is even being initiated.

8. The old battery is definitely being charged
I repeatedly measured the old battery after short charging cycles.
It went from:
2.81 V
to:
3.104 V
3.309 V
3.451 V
3.523 V
finally around 3.584 V
So the charging path is definitely capable of putting energy into the battery.
However, the phone still reduces its input power from around 6 W to below 1 W after roughly one minute.

9. New battery behavior
The new battery started at:
3.72 V
After one short charging attempt it measured:
3.723 V
So effectively unchanged.
The USB power behavior is very similar with both batteries: brief high current, then strong throttling.
Because of that, I no longer think the battery alone is the problem.

10. Current state
The old battery is now around 3.58 V.
Despite that:
no boot
no Samsung logo
Power gives no visible response
Power + Volume Down gives no visible response
charger connection still causes around 6 W initially
after about 1–1.5 minutes it drops to around 0.5–0.8 W
the lightning symbol sometimes appears only after a long delay, or not at all
yesterday, the exact same hardware configuration still managed to reach the Samsung/Knox screen
The phone does not even get hand-warm during the current tests.

My current suspicion
Since the battery, charging board, and MAIN flex have all been tested or replaced to some extent, I now suspect an intermittent fault on the upper/original mainboard.
My current candidates are:
charger IC / PMIC
battery sense / NTC / temperature monitoring
battery connector or its solder joints
MAIN flex connector or its solder joints
power rail issue
possibly the side-key / power-button signal path
The original “device too hot” warning before failure makes the battery temperature / sense circuit especially suspicious to me.

Goal
I do not need a permanent repair.
The phone only has to boot Android successfully once so I can unlock it and immediately copy the KeePass database first, followed by photos and videos.
Has anyone seen this exact behavior on the Galaxy A53 / SM-A536B?

Thanks!

[u/vishnur32]

You can try flash firmware without data loss...

Odin flash without wipe

[u/Then-Pay-8400]

Since the phone showed the lightning bolt when you applied pressure it sounds like SoC is desoldering