VGA Adapter Fire Incident: Possible Causes and Prevention Tips

[DeepSeeded]

I came into work this morning and someone had started to plug their monitor into their laptop via VGA port and it caught fire for a moment, burnt the metal a bit and the internals. A vga cable is only 5v and 5ma, how is this possible?

The laptop was running only off the battery which still had a full charge afterwards.

It takes thousands of volts at very low resistance to burn metal, correct?

 

[berkeman]

I came into work this morning and someone had started to plug their monitor into their laptop via VGA port and it caught fire for a moment, burnt the metal a bit and the internals. A vga cable is only 5v and 5ma, how is this possible?

The laptop was running only off the battery which still had a full charge afterwards.

It takes thousands of volts at very low resistance to burn metal, correct?

What part exactly caught fire? The CRT monitor?

There are protections against this happening, but most likely something in the monitor failed. There could also have been something metallic dropped into the CRT enclosure causing a short, but unless there's a bunch of junk sitting on top of the CRT enclosure, this is pretty unlikely.

Glad nobody was hurt, and that the fire did not spread. Was it an actual fire with flames, or a smoked component?

 

[DeepSeeded]

It was a small very quick electrical fire, she said there was also a huge spark that shot out at her. That would require about 3 million volts per square meter and the area of the metal edge of the vga port is not a sharp point.

It was only in the plug, nothing within the monitor or computer. The monitor should be sending most of the electricity to the mercury tube and not the vga adapter.

 

[berkeman]

It was a small very quick electrical fire, she said there was also a huge spark that shot out at her. That would require about 3 million volts per square meter and the area of the metal edge of the vga port is not a sharp point.

It was only in the plug, nothing within the monitor or computer.

Two things. Please don't throw numbers around when you're not understanding things. "3 million volts per square meter" means nothing.

Second, if the spark came from the plug as it was connected, there is a possible problem with the wiring at that station. It would be best if you could check all the outlets there with a simple circuit tester (the 3-prong plastic things you get at the hardware store for $10), or have your company's facilities folks take a look.

Has this connection been made in the past with no problems? Does the monitor work now, or is it broken? Was it a dry day, BTW? It's possible that there was a static shock at the connector when plugging in the laptop, and that caused a latchup and fuse pop in the monitor...

 

[DeepSeeded]

Two things. Please don't throw numbers around when you're not understanding things. "3 million volts per square meter" means nothing.

3 mil v per square meter is roughly the minimum for corona discharge, sparks didn't just fly between the connection but out from the plug into the air...

It's not extra dry today.

You think the electrical outlet could have been sending more power to the monitor? It is plugged into a UPS.

The monitor is still turning on and putting 5v out the vga plug.

 

[berkeman]

3 mil v per square meter is roughly the minimum for corona discharge, sparks didn't just fly between the connection but out from the plug into the air...

It's not extra dry today.

You think the electrical outlet could have been sending more power to the monitor? It is plugged into a UPS.

It most likely was just a component burning up, or at most a 110Vrms fault in the electrical wiring. Does your company have an Emergency Response Team, preferably with some EEs on it? (My company does...I'm on it.) If not, does your Facilities group have reasonable electrician/electrical skills? This problem needs to be understood and fixed before that station gets used again. Burning components and smoke are not good things.

BTW, when a component let's go and pops, it can be noisy, smoky, and there can be bright flashes (and even fire). That doesn't mean that there's been a corona discharge involving very high voltages. That having been said, the CRT monitor does use voltages in the 25kV range for a color monitor, and faults involving that tube voltage can be pretty spectacular.

 

[DeepSeeded]

We don't have any electrical engineers, I only know what I have learned in physics which isn't so helpful with real world circuit troubleshooting.

I am trying to figure out if the problem was caused by the monitor or the laptop, I assume the monitor since the laptop's only power source was the battery and the battery had a full charge right after.

 

[berkeman]

I am trying to figure out if the problem was caused by the monitor or the laptop, I assume the monitor since the laptop's only power source was the battery and the battery had a full charge right after.

Yes, that's a good assumption. If the laptop was floating (not plugged into a wall socket), then its not a ground/power loop problem.

What is the condition of the display? You said the main damage is in the connector? What does it look like? BTW, are all the pins straight? If a pin had gotten bent, and plugging in the laptop pushed a power pin over against a ground or the shell, that could create an arc whose size would depend on the monitor's circuit that feeds power to the connector.

 

[DeepSeeded]

No bent pins.

The monitor is working but flashing on and off.

I guess that means there was a short in the monitor's internal circuit. She never even got to the point where one of the pins entered the holes. Only the outer metal edge (the negative part) was touched as she was about to plug it in.

 

[DeepSeeded]

As an added note one of the positive pins could have touched the negative easily, this happens all the time, that would have shorted the entire circuit. But the tiniest amount of internal resistance would have kept it at bay.

 

[berkeman]

No bent pins.

The monitor is working but flashing on and off.

Sounds like that monitor needs to be sent out for repair or recycle. It's too big of a liability to keep around in its present state. Just think of what would happen if the sucker really did catch fire now, and caused some damage or injury. Bad scene.

As they say in law enforcement, "Bad Order that thing" (mark it as BO for repair).

 

[DeepSeeded]

The monitor smells a little burnt inside, getting a new monitor. The laptop is still putting out external video amazingly. I would expect even if the monitor shorted out, the resistance in the video card should have made up for it, and if the monitor was sending extra voltage then the video card should be fried for sure. Odd.

Thanks for your help.