Editing Openai/691fd47a-4338-8002-8886-35bc70dbf9b5 (section)

== gpt-5-1 ==
=== User: why did this power supply board burn and smoke ===
why did this power supply board burn and smoke

=== Assistant: From the condition of the board in your photo, the most likely causes of burn + smoke come from common failures in smal… ===
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:

=== ✅ 1. Most likely failure: Primary-side capacitor or MOV failure ===

On the top-left, the blue disk components (MOV surge suppressors) and the yellow “safety capacitor” look aged.
If a MOV is overstressed by a power surge, it can short → pull huge current → burn and smoke.

Clues on your board:
* Blue MOVs look slightly darkened.
* Area near the AC input looks heat-stressed.

=== ✅ 2. Transformer insulation breakdown ===

Your main SMPS transformer (center) shows brown stains / melted varnish.
This means:
* Internal winding overheated
* Insulation melted
* Transformer began to arc internally → smoke

This is a VERY common failure when:
* The switching MOSFET shorted
* The controller IC ran full-power
* A primary capacitor dried up and caused voltage spikes

=== ✅ 3. Shorted rectifier diode or switching transistor ===

On the hot side (right side of board), the large heatsink-mounted switching transistor or rectifier could have shorted.

A shorted transistor → huge current → burns the transformer and primary resistor.

You can see some darkened PCB around the hot-side components.

=== ✅ 4. Electrolytic capacitor failure (common cause) ===

The SAMXON capacitor on the right side is a brand known for failures.
If this capacitor went bad (ESR increases), ripple increases → MOSFET overheats → transformer overheats → smoke.

Even if it’s not visibly bulged, it may be internally failed.

=== ✅ 5. Glue turning conductive ===

The yellow/brown glue around coils often becomes conductive and corrosive when old.

Your board clearly has old glue around the:
* output coil
* transformer
* capacitors

When conductive glue bridges traces → short circuit → smoke.

=== 📌 Which component looks burned? ===

From the image, the transformer is the most obviously heat-damaged component, showing brown leakage/stains.
This means something upstream (MOSFET, capacitor, or feedback circuit) caused an overload.

=== 🚨 Final conclusion ===

Your power supply board likely burned due to a primary-side failure, most likely:
# Bad capacitor → unstable switching → MOSFET short → transformer overheated
# MOV surge suppressor failure
# Conductive glue causing a short

Once the MOSFET or transformer shorts, massive current flows—causing smoke.

If you want, I can:
🔧 Identify suspect components one-by-one
🔧 Guide you on what to test with a multimeter
🔧 Tell you whether this board is repairable or should be replaced

Just send a close-up picture of the burnt area or underside.