A flickering center lamp in a three-module COB LED fixture eventually stopped working completely in the first-floor common stairwell of a residential building in Hannam-dong, Seoul.
Replacing the entire fixture would normally have been the simplest solution. In this case, however, the original model had been discontinued, and a replacement with the same dimensions and appearance was no longer available.
Instead, we diagnosed the failed component, identified a compatible COB LED module with the assistance of ChatGPT, confirmed the part with an electrical supplier, and repaired the original fixture.
| Location | Hannam-dong, Seoul, South Korea |
| Building Area | First-floor common stairwell of a residential building |
| Fixture | Triple COB LED downlight |
| Fixture Size | Approx. 450 × 145 mm |
| Failure | Center COB flickered and eventually stopped illuminating |
| Diagnosis | Failed COB LED module |
| Repair | Replacement of the failed COB module only |
A Rainy Service Call in Seoul
The service call took us from Gangnam to Hannam-dong.
As we crossed Dongho Bridge, the Han River was almost hidden beneath the gray sky. It was a hot and humid rainy summer day, but electrical maintenance work continues regardless of the weather.
The destination was a residential building where three identical triple COB LED fixtures had been installed in the common stairwell.
Driving from Gangnam to Hannam-dong, overlooking the Han River near Dongho Bridge on a rainy summer day.
1. The Failure: A Flickering Center COB
The problem was immediately visible.
The center COB LED had initially been flickering intermittently and eventually stopped illuminating completely. The COB modules on both sides continued operating normally.
Because the fixture used three separate COB LED modules, each powered by its own independent constant-current LED driver, there were two primary suspects:
- the LED driver supplying the center COB, or
- the COB LED module itself.
.png "Failed Center COB in Triple LED Downlight")
The triple COB LED fixture with the center module failed while the two outer modules remained operational.
The failed component was not identified by appearance alone.
A known-good LED driver was connected to the failed COB, but the COB still did not illuminate. The suspected driver was then connected to a known-good COB, and that COB operated normally.
This cross-test isolated the failure to the COB LED module rather than the driver.
2. Isolating the Fault by Cross-Testing
Before disassembly, the circuit breaker supplying the lighting circuit was switched off.
The entire fixture had to be removed from the ceiling even though only one COB module needed replacement.
After gaining access to the internal components, we performed a two-way cross-test using the functioning components already installed in the fixture.
Test A — Known-Good Driver to Failed COB
One of the working LED drivers from an adjacent module was connected to the failed center COB.
The COB remained off.
Test B — Suspected Driver to Known-Good COB
The driver originally connected to the failed center COB was then connected to a working COB module.
The known-good COB illuminated normally.
With both tests producing consistent results, the LED driver could be ruled out and the center COB module was confirmed as the failed component.
There were no obvious burn marks, cracks, or visible signs of damage on the failed COB.
The exact cause of failure could therefore not be determined. Because the light is installed in a common stairwell and operates for long periods every day, normal long-term degradation may have contributed, but this could not be confirmed.
The triple COB LED downlight disassembled for component-level diagnosis.
3. Reading the LED Driver Specifications
The next challenge was finding a compatible replacement COB.
The failed COB itself had no useful model number or electrical specifications printed on it. That meant the replacement could not be identified simply by reading the module.
However, the dedicated constant-current LED driver contained useful electrical information.
| Parameter | Specification |
|---|---|
| Input Voltage | 220–240 V AC, 50/60 Hz |
| Maximum Input Current | 0.2 A |
| Output Voltage | 25–42 V DC |
| Rated Output Current | 700 mA |
| Rated Output Power | 29.4 W |
| Power Factor | 0.9 |
| COB Diameter | Approx. 20 mm |
| Color Temperature | Approx. 4000 K, matched to the existing lighting |
.png "LED Driver Specifications Used to Identify a Compatible COB Module")
The constant-current LED driver provided the electrical specifications needed to narrow down the compatible COB module.
4. Using AI to Narrow Down an Unmarked COB Module
This was where AI became useful.
A colleague working with me photographed the components from several angles and used ChatGPT to analyze approximately three images together with the driver specifications.
The most useful information was the combination of:
- 25–42 V DC driver output range,
- 700 mA constant-current output,
- 29.4 W rated output power,
- the physical size of the COB, and
- the component photographs.
ChatGPT did not definitively identify a specific replacement part.
Instead, it helped narrow the search from an unknown, unmarked LED component to a much smaller range of COB modules with electrical characteristics likely to be compatible with the existing driver.
That distinction is important.
For field electrical work, an AI-generated answer was not treated as final confirmation of component compatibility.
ChatGPT helped narrow the search quickly, but the final component selection was verified with a supplier who handles these parts directly.
AI accelerated the investigation. It did not replace technical judgment, supplier verification, or the electrician's final safety decision.
5. Confirming the Part with an Electrical Supplier
After narrowing down the likely specifications, we contacted one of our regular electrical suppliers in Cheonggyecheon, Seoul.
We sent the supplier photographs of the existing COB together with the electrical specifications identified from the driver.
The supplier confirmed that the COB could be replaced independently and identified a compatible module.
This second verification was important because a supplier who handles the actual components can confirm practical compatibility more reliably than relying solely on an AI prediction.
The replacement component was then sent directly to the job site by motorcycle courier.
Using AI to narrow the search meant that we could describe the required component much more precisely from the beginning, reducing the time needed to locate the correct part.
The compatible replacement COB LED module delivered to the job site after confirming the specifications with the supplier.
6. Why Repairing the Original Fixture Made Sense
Component-level repair was especially valuable in this case because replacing the complete fixture presented several problems.
Three identical fixtures were installed together in the stairwell, and the original model had been discontinued.
The existing fixture measured approximately 450 × 145 mm, and according to the supplier, a new fixture with the same dimensions was not readily available.
Even if another fixture could have been adapted to the opening, there was a strong possibility that its appearance would differ from the other two fixtures.
Replacing only the failed COB allowed us to retain:
- the existing ceiling opening,
- the original fixture body,
- the visual consistency of all three stairwell fixtures, and
- the majority of components that were still functioning correctly.
7. Replacing the COB and Restoring Thermal Contact
High-power COB LEDs concentrate substantial heat into a very small area.
For this reason, good thermal contact between the COB substrate and the aluminum heat sink is essential.
The original module had thermal compound between the COB and its mounting surface.
After removing the failed COB, the old thermal compound was completely cleaned from the contact surface.
A fresh layer of thermal compound was then applied.
Only a thin layer was used—enough to fill microscopic gaps between the two surfaces rather than creating an unnecessarily thick layer.
The new COB was positioned on the heat sink, secured with screws, and connected using the fixture's existing connector system.
A thin layer of fresh thermal compound was applied between the replacement COB module and the aluminum heat sink.
The replacement COB LED module before final installation and reassembly.
8. Reassembly and Operational Testing
Once the new COB had been installed, the fixture was fully reassembled and returned to the ceiling.
Power was restored and all three COB modules illuminated normally.
The repaired fixture was not judged only by a momentary power-on test. It was left operating for a period of time so that we could observe whether the repaired module remained stable.
No further flickering or abnormal operation appeared during the observation period.
The replacement COB also matched the existing modules closely in both brightness and light color, preserving the appearance of the original fixture.
All three COB modules operating normally after the completed repair.
9. The Result: Preserving a Discontinued Fixture
The final result was more than simply restoring one failed light.
A discontinued fixture that would have been difficult to replace without modifying the ceiling or changing the appearance of the stairwell was returned to normal operation by replacing only the failed internal component.
The building manager was relieved and told us that it was good to see the fixture repaired successfully.
For a technician, comments like that are rewarding.
The unfamiliar part had initially made the repair less straightforward, but combining conventional electrical diagnosis, supplier experience, and AI-assisted component research allowed the problem to be solved efficiently.
10. Field Lesson: Where AI Actually Helps an Electrician
This repair illustrates a practical role for artificial intelligence in electrical fieldwork.
AI did not determine whether the circuit was safe. It did not perform the electrical diagnosis, remove the fixture, select the final component, apply the thermal compound, or verify the completed repair.
Those decisions remained the responsibility of the technicians.
What AI did well was reduce the time required to investigate an unfamiliar component.
When electricians encounter equipment or new products they do not recognize, having an AI system analyze photographs together with known electrical specifications can quickly narrow the range of possibilities.
I also use AI in fieldwork for tasks such as checking allowable current values, calculating electrical loads, estimating power consumption, and working out equal spacing for lighting installations.
The limitation is equally important:
AI-generated information should not be treated as the final authority for electrical safety or component compatibility.
Measurements, actual equipment specifications, professional experience, supplier or manufacturer information, and final human verification still matter.
In this case, AI helped us order the correct type of component faster and solve a problem involving a part we were initially unfamiliar with.
Seeing the repaired fixture operating normally—and hearing the building manager say that it was fortunate we could repair it—made the result particularly satisfying.
Diagnosis first: Cross-testing the independent LED drivers and COB modules isolated the actual failed component.
Use available data: When the COB itself had no markings, the driver's 25–42 V DC, 700 mA, and 29.4 W specifications provided essential clues.
AI as a search accelerator: ChatGPT narrowed the component search but did not make the final compatibility decision.
Human verification remains essential: The supplier confirmed the replacement part, and the final installation and safety decisions remained with the technicians.
Electric Korea
Korean Electrical Construction · Field Experience · Safety · Technical Education
Website: electrickorea.co.kr
.png)
.png)
.png)
