Amazfit T-Rex Pro works only on the charger: power circuit repair
Amazfit T-Rex Pro worked only on its charger. The battery was good; the fault was in the motherboard power circuit. Board repair restored normal operation.
Amazfit T-Rex Pro working without the charger again after a motherboard power circuit repair.
This Amazfit T-Rex Pro arrived with a fault that can easily lead to the wrong conclusion: the watch worked while connected to its charger, but stopped as soon as the charging cable was removed. The obvious suspect was a worn or failed battery. In this case, however, fitting a new battery would not have solved the problem.
Diagnostics showed that the battery was not the cause. The fault was in the motherboard power circuit. After repairing the affected section, the watch regained normal standalone operation: it starts without the charger, runs reliably from the battery and charges correctly.
What the fault looked like
While the Amazfit T-Rex Pro was on its charger, it showed signs of life and could operate. Once removed from the charger, power disappeared. The same symptom can be caused by a failed battery, a poor battery connection, deep discharge or a fault in the electronics that manage and distribute power.
Customers commonly describe this problem in several ways:
- the watch works only on the charger;
- it switches off immediately after the charger is removed;
- it displays a battery percentage but cannot run on battery power;
- it restarts during boot or under load;
- charging is detected, but stored energy is not used;
- leaving it on charge for longer makes no difference.
These descriptions identify a symptom, not a confirmed component failure. The battery and the entire power path must be checked before replacement parts are ordered.
Why the battery was not replaced
A rechargeable battery is a wear item and its capacity naturally falls with age. Nevertheless, a motherboard fault can create almost identical behaviour. Possible causes include a poor connection, an interruption or abnormal resistance in a power rail, moisture damage, or a defective part in the power-management section.
On this watch, diagnostics separated a possible battery issue from the actual electronic fault. The battery did not require replacement. The problem was localised to the motherboard power circuit, which prevented the watch from using its own stored energy correctly.
This distinction matters: a replacement battery would have added cost and delay while leaving the original fault untouched.
Amazfit T-Rex Pro power circuit repair
Once the fault had been localised, the affected part of the power circuit was repaired at board level. Work inside a smartwatch requires controlled disassembly, precise access to a compact multilayer board and careful testing before final reassembly.
After the repair, we checked:
- startup with no charger connected;
- stable operation from the battery;
- correct charger detection;
- charging and battery-level indication;
- absence of unexpected shutdowns and restarts;
- the display, buttons and core functions after reassembly.
The watch passed the checks and returned to full working order.
Why diagnosis should come before a battery replacement
“Works only on the charger” is useful information, but it is not a complete diagnosis. When the fault is on the motherboard, a new battery cannot fix it.
A proper diagnosis should establish:
- whether the battery can accept and deliver energy;
- whether battery power reaches the required circuits;
- whether motherboard power management operates correctly.
Only then can the correct repair be chosen. In this case, the existing battery was retained and the real cause was repaired on the board.
What to do when an Amazfit T-Rex Pro works only while charging
Avoid leaving the watch on charge for days, repeatedly forcing it to start or buying a battery based only on the symptom. Bring the watch for diagnosis, preferably with its charging cable. Mention whether the behaviour began after a drop, contact with water, overheating or a long period without use.
After any smartwatch has been opened, its original water-resistance rating should not be treated as guaranteed, even after careful resealing. A repaired watch should not be deliberately submerged or used where complete sealing is critical.
Amazfit repair in Belgrade and service for customers across Serbia
MyService provides diagnostics and smartwatch repair for the Amazfit T-Rex Pro and other Amazfit models. Our work covers more than batteries and displays: we also diagnose charging, power, button, sensor and motherboard faults.
Customers outside Belgrade can contact us before sending a watch from another city in Serbia. Provide the exact model and a detailed description of the behaviour so we can recommend the next step.
Repair result: the Amazfit T-Rex Pro now starts and operates normally without the charger. The battery did not need replacement; the faulty motherboard power circuit was repaired.
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