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{{DISPLAYTITLE:SMPS failure causes}}<br />
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''This conversation was exported from ChatGPT''<ref>{{cite web|title=SMPS failure causes|url=https://chatgpt.com/share/691fd47a-4338-8002-8886-35bc70dbf9b5|publisher=ChatGPT|access-date=2025-11-27}}</ref><br />
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== gpt-5-1 ==<br />
=== User: why did this power supply board burn and smoke ===<br />
why did this power supply board burn and smoke<br />
<br />
=== Assistant: From the condition of the board in your photo, the most likely causes of burn + smoke come from common failures in smal… ===<br />
From the condition of the board in your photo, the most likely causes of burn + smoke come from common failures in small SMPS (switch-mode power supply) boards. Here’s what I can see and what typically happens:<br />
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=== ✅ 1. Most likely failure: Primary-side capacitor or MOV failure ===<br />
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On the top-left, the blue disk components (MOV surge suppressors) and the yellow “safety capacitor” look aged.<br />
If a MOV is overstressed by a power surge, it can short → pull huge current → burn and smoke.<br />
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Clues on your board:<br />
* Blue MOVs look slightly darkened.<br />
* Area near the AC input looks heat-stressed.<br />
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=== ✅ 2. Transformer insulation breakdown ===<br />
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Your main SMPS transformer (center) shows brown stains / melted varnish.<br />
This means:<br />
* Internal winding overheated<br />
* Insulation melted<br />
* Transformer began to arc internally → smoke<br />
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This is a VERY common failure when:<br />
* The switching MOSFET shorted<br />
* The controller IC ran full-power<br />
* A primary capacitor dried up and caused voltage spikes<br />
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=== ✅ 3. Shorted rectifier diode or switching transistor ===<br />
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On the hot side (right side of board), the large heatsink-mounted switching transistor or rectifier could have shorted.<br />
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A shorted transistor → huge current → burns the transformer and primary resistor.<br />
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You can see some darkened PCB around the hot-side components.<br />
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=== ✅ 4. Electrolytic capacitor failure (common cause) ===<br />
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The SAMXON capacitor on the right side is a brand known for failures.<br />
If this capacitor went bad (ESR increases), ripple increases → MOSFET overheats → transformer overheats → smoke.<br />
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Even if it’s not visibly bulged, it may be internally failed.<br />
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=== ✅ 5. Glue turning conductive ===<br />
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The yellow/brown glue around coils often becomes conductive and corrosive when old.<br />
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Your board clearly has old glue around the:<br />
* output coil<br />
* transformer<br />
* capacitors<br />
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When conductive glue bridges traces → short circuit → smoke.<br />
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=== 📌 Which component looks burned? ===<br />
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From the image, the transformer is the most obviously heat-damaged component, showing brown leakage/stains.<br />
This means something upstream (MOSFET, capacitor, or feedback circuit) caused an overload.<br />
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=== 🚨 Final conclusion ===<br />
<br />
Your power supply board likely burned due to a primary-side failure, most likely:<br />
# Bad capacitor → unstable switching → MOSFET short → transformer overheated<br />
# MOV surge suppressor failure<br />
# Conductive glue causing a short<br />
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Once the MOSFET or transformer shorts, massive current flows—causing smoke.<br />
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If you want, I can:<br />
🔧 Identify suspect components one-by-one<br />
🔧 Guide you on what to test with a multimeter<br />
🔧 Tell you whether this board is repairable or should be replaced<br />
<br />
Just send a close-up picture of the burnt area or underside.<br />
<br />
== References ==<br />
<references /><br />
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[[Category:ChatGPT Shares]]<br />
[[Category:openai]]</div>Lukegao