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Fault from powering with excess voltage

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KatGND

New Member
Good day everyone!

I have a hair straightener that I’d like to repair. Recently I was traveling and I was powering the device with a voltage converter that delivered too much voltage. The device is rated for 100V, and the converter delivered 120V.

The straightener worked for a while, and eventually I heard a pop, and the device failed. If I plug it in and try to turn it on, the LED doesn’t light up and the heating elements don’t warm.

Looking at the underside of the PCB, I can see that there’s quite a bit of carbon residue around some of the solder pads. The scorching seems to come from the wires that connect to the heating elements. There’s no scorching on the top of the PCB where the components are located.

None of the wires on the device look like the plastic melted. Also, some of the wires are a bit more exposed than I’d expect. I’m not seeing that any of the exposed wires are touching each other. Though, some of the exposed wire do touch the PCB around the edges.

All of the components look just fine… unless there are components inside the second half of the device. I didn’t disassemble that half.

I’m fairly new to hobby electronics and my electrical theory is very limited, but I want to learn! I’d be so grateful for any guidance on how to diagnose the exact problem and how to subsequently repair it.

Summary
Device: Hair straightener
Brand: GAMA Italy
Age: 7+ years
Cause of fault: powered with 120V when rated for 100V
Symptom: Popping sound, device does not warm and LED doesn’t light. Bottom of PCB scorched

Images
Overview of device


Closeup of top of PCB that receives voltage input


Reverse of PCB


Some images showing the components on the top of the PCB


 
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spec

Well-Known Member
Most Helpful Member
Hy Kat,

Welcome to ETO. I see you are from Canada.

Shame about your hair straightener going pop.

It is difficult to fault find at a distance, but at a guess the switch has burnt out. Does it smell. Is it now hard to move.

I don't think the diode (1N4007) plays any part in the heating function. I think it, and the resistor are there just to illuminate the LED. It is unlikely that any of those components would have failed by an over voltage of 20V.

What electronic skills do you have. Do you have a multimeter and soldering iron etc. If not it will be impossible and dangerous to progress any further. Please let me know.

I don't mean to be unkind, but as the hair straightener is 7 years old. I would strongly advise you to junk it and buy a new one.

By the way, nice pictures and description.

spec
 
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ericgibbs

Well-Known Member
Most Helpful Member
Hi,
I would say the heating elements have failed short circuit, running at 120v versus 100v would be a ~40% overdrive.
A short should have blown the plug safety fuse, if not, the switch has burnt 'open'.
The LED may have also failed.

My advice would be NOT to attempt a home repair, throw it in the trash bin.

E
 

SPDCHK

Member
For what its worth,

My wife's straightener from time to time keeps making beeping sounds. (Beeps once when you plug it in and then it should be quiet).

I found that the rotary connection (where the power lead enters the straightener) opened up a bit, causing bad connection. I just used pair of long-nose pliers and closed the gap down again. The worked fine for about a year, and then did the same thing again. Having fixed it once before I did the same procedure again. We are still within our second year ;)

BUT, I did buy the wife a new one, but she's one of those people who will use something till it falls apart. So the new one is patiently waiting for its first use one day.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
That's like "no big deal".

You basically have a switch, a lamp and a heating element.
The lamps consists of the resistor, LED and diode. All standard.

On your PCB picture, it looks like you have a broken trace. Follow the blue wire.

The switch or the heating element could have failed or the trace itself was the only failure.

I don't like the blob between the two switch contacts.

The PADS labeled PTC was probably for a a ZNR which is a surge protection device.
 

KatGND

New Member
Reply to other forum

Hey everyone! Thanks for the replies. Before I get to them, I opened up the other side of the hair straightener and found some more components. Nothing visually seems to be wrong with the components on this side.

It is difficult to fault find at a distance, but at a guess the switch has burnt out. Does it smell. Is it now hard to move.

I don't think the diode (1N4007) plays any part in the heating function. I think it, and the resistor are there just to illuminate the LED. It is unlikely that any of those components would have failed by an over voltage of 20V.

What electronic skills do you have. Do you have a multimeter and soldering iron etc. If not it will be impossible and dangerous to progress any further. Please let me know.

I don't mean to be unkind, but as the hair straightener is 7 years old. I would strongly advise you to junk it and buy a new one.
Hey Spec! Thanks for the welcome and reply. It is a shame, isn’t it?

Following your lead on the switch, I noticed that it doesn’t seem to have any odour and it’s also not hard to move. Hmmm… Regardless, thanks for the information about the diode and resistor. I’ll note that I can probably rule them out as the cause.

As far as my electronics skills, they are very basic. I have a multimeter, a soldering station, and some other tools. I’ve practiced soldering a bit and have built a couple of small hobby projects from kits. I really have no technical understanding about electronics. I can basically follow recipes like a baker would, and that’s it.

*grins* It’s not unkind at all! I’m just a bit too stubborn to let go without trying something.


Hi,
I would say the heating elements have failed short circuit, running at 120v versus 100v would be a ~40% overdrive.
A short should have blown the plug safety fuse, if not, the switch has burnt 'open'.
The LED may have also failed.

Hey Eric! Thanks for the feedback on the different components. I’m actually surprised that I don’t see some type of safety fuse anywhere.

Anyway, following your lead, I’ve used my multimeter to test along the heating elements, switch, and LED for continuity to see if I can determine what has stopped working. The switch shows continuity on both sides, the LED shows continuity, and the elements show continuity from one solder pad to the next.

For what its worth,

My wife's straightener from time to time keeps making beeping sounds. (Beeps once when you plug it in and then it should be quiet).

I found that the rotary connection (where the power lead enters the straightener) opened up a bit, causing bad connection. I just used pair of long-nose pliers and closed the gap down again. The worked fine for about a year, and then did the same thing again. Having fixed it once before I did the same procedure again. We are still within our second year 
I noticed that the problem you’re describing was all over the internet while I was researching hair straightener repairs! I’ll keep my eye out for that problem on mine too, thanks!

That's like "no big deal".

You basically have a switch, a lamp and a heating element.
The lamps consists of the resistor, LED and diode. All standard.

On your PCB picture, it looks like you have a broken trace. Follow the blue wire.

The switch or the heating element could have failed or the trace itself was the only failure.

I don't like the blob between the two switch contacts.

The PADS labeled PTC was probably for a a ZNR which is a surge protection device.
Amazing! After I cleaned up the carbon on the board with some isopropyl alcohol, I can also clearly see the broken trace on both sides of the board.



I checked along the various components for continuity, and unless I’m mistaken, after mapping out what has continuity, it seems like it’s just the trace that’s the point of failure.

Here’s an image showing what I found. Anything connected with a red line has continuity among each other. A green circle is a component point, a black slash is where continuity is lost. An arrow shows continuity but only in that direction.




After doing a bit of research on how to repair burnt circuit traces, it seems like many people suggest using a small piece of tinned wire along the broken trace.

Would I use the tinned wire from the two components on either side of the trace? It seems like the trace encompasses two components at once on the far left. Hmmm... I'm a bit unsure of the safest way to do this.
 
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Les Jones

Well-Known Member
Most Helpful Member
Hi Kat,
It looks like something in the heater part has shorted out. The two places where there is an open circuit look like they have behaved as a fuse and melted due to excessive current. What is the resistance reading between the blue and black wire on the left of the last picture ? Can you post a picture of the components in the other side of the item. I think the evidence from your measurements Makes it more likely that it is not repairable than when we all thought the switch had failed.

Les.
 

spec

Well-Known Member
Most Helpful Member
Hey Spec! Thanks for the welcome and reply. It is a shame, isn’t it?

Following your lead on the switch, I noticed that it doesn’t seem to have any odour and it’s also not hard to move. Hmmm… Regardless, thanks for the information about the diode and resistor. I’ll note that I can probably rule them out as the cause.

As far as my electronics skills, they are very basic. I have a multimeter, a soldering station, and some other tools. I’ve practiced soldering a bit and have built a couple of small hobby projects from kits. I really have no technical understanding about electronics. I can basically follow recipes like a baker would, and that’s it.

*grins* It’s not unkind at all! I’m just a bit too stubborn to let go without trying something.
Hy Kat,

Your skills, logical approach, and equipment will allow you to fault-find and repair your hair straightener.:)

I like your resolve about trying to fix something as a challenge- many ETOnions feel the same.:)

But, please do not consider plugging that device in the mains supply again.:eek:

For one thing I like ladies with curly/wavy hair, but the main thing is: because your hair straighter has been badly over stressed it will be dangerous, even if repaired, particularly when considering the application. Also it is relatively low cost.

By the way, when my wife had long hair, I used to iron it for her - thru brown paper on an ironing board - so it hung down in sheets.:cool:

spec
 
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KeepItSimpleStupid

Well-Known Member
Most Helpful Member
Failure analysis:

The lack of the missing component reduced the current carrying capacity of the trace by reducing the cross sectional area. Had that component or dummy lead been installed, the entire width of the trace would have be availabe to carry current.

You want a wire with at least the same cross sectional area of the trace.

You should insert a dummy component (just a soldered wire) or a "solder bridge" on the other side. Your black marks.
 
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