Fixing a Dead Blowdryer: Safety Tips

[karen03grae]

My blowdryer just died a couple of days ago. I was going to repair it myself but I was afraid of being shocked. Now I have a new one, but I hate to see the old one go to waste. Truth is, I really*emphasis* want to take it apart and see how it works. However, my new dryer's manual states "DO NOT ATTEMPT TO REPAIR IT YOURSELF...electrical parts are electrically live even when the switch is off."

I assume this is because it has a capacitor.

I wanted to know if there is any safe way of taking it apart and examining it. If not...oh well

 

[Averagesupernova]

They are covering their azzes with that warning.

 

[Cliff_J]

Couple things:

It should be safe if it is completely unplugged from the power outlet. Capacitors only store DC energy, the outlets are all AC and unless it was some super fancy variable speed unit (not two speed, but continously variable) it would stay AC throughout. If plugged in it should be considered dangerous and treated with respect.

If it died, it has likely burned up a part that would cost nearly as much or cost more to replace than to purchase a whole new unit. Its not like the parts are that expensive but in a quantity of one it would be rare to find and shipping and distributor markups et cetera would make it expensive. A whole new hair dryer costs what, $15-20? So it should be no problem to trash the old one after you've taken it apart.

Cliff

 

[NoTime]

1) Make sure it is unplugged!
2) Make sure it is unplugged!
3) Make sure it is unplugged!

A bigger problem is if you fix it wrong.
Or put it back together wrong.
It could start a fire or electrocute you.

There won't be any residual charge in a blowdryer, unlike some electronic equipment.

 

[enigma]

If there are any capacitors, you can carefully discharge them with a voltmeter. Just be sure you don't touch the leads with your fingers.

 

[karen03grae]

If there are any capacitors, you can carefully discharge them with a voltmeter.

I don't have a voltmeter; if I see a capacitor is there any other way to discharge it? Maybe I'll just work around the cap. And no, I wasn't planning on putting it back together and using it again. That is way too risky and I am not an electrician. I'm just going to take it apart and analyze it.

It's going to be fun! I have to deform (smash) it to get it open because there are no screws holding it together. :(

But thanks for your input..

-Karen

 

[brewnog]

if I see a capacitor is there any other way to discharge it?

Absolutely. Just cross the terminals with something which isn't your finger. (Something metal would help here.)

 

[karen03grae]

Today I officially diassembled my dryer. Vidal Sassoon makes a tough product. But to my dismay, there were only resistors and a small metal piece (unknown). No capacitors. Wish I had a camera to show those who are interested. Next, I am going to dissect my old cell phone...

 

[brewnog]

Good for you! I think most of the people in the Engineering forum here have spent many happy hours taking things to bits (and sometimes even putting them back together again!).

Have fun with your dissecting. Just be careful with things like cameras (which can have some VERY big capacitors in them for the flash).

 

[russ_watters]

Bah - as long as you de-energize it by laying a nail across the terminals of the capacitor...

 

[DaveC426913]

Couple things:

It should be safe if it is completely unplugged from the power outlet. Capacitors only store DC energy, the outlets are all AC and unless it was some super fancy variable speed unit (not two speed, but continously variable) it would stay AC throughout. If plugged in it should be considered dangerous and treated with respect.

Cliff

Holy Jeez - next you'll be telling him his microwave oven should be good for drying his hair...


It is trivial to turn AC into DC. You need two components - one is a diode and the other is a capacitor!

 

[Cliff_J]

Are you suggesting that telling someone new to experimenting with electrical items to unplug the device for their own safety is akin to doing something that would be harmful?

 

[Math Is Hard]

Today I officially diassembled my dryer. Vidal Sassoon makes a tough product. But to my dismay, there were only resistors and a small metal piece (unknown). No capacitors. Wish I had a camera to show those who are interested. Next, I am going to dissect my old cell phone...

I was just reading this thread and thinking I would really like to see the inside of that blowdryer - I wonder if karen will post pictures? That might actually make a neat web project- you could put up pictures of things you've taken apart like blowdryers and cell phones.

 

[Delta]

I was just reading this thread and thinking I would really like to see the inside of that blowdryer - I wonder if karen will post pictures? That might actually make a neat web project- you could put up pictures of things you've taken apart like blowdryers and cell phones.

Well, I've got a picture of a disected super soaker gun if anyones intereseted

On the topic of taking things apart safely it should be noted that there are indeed dangers lurking inside, EVEN IF they are disconnected from supply

Obviously equipment that's just been used may get very hot, so let them cool for some time before going to work.

As above capacitors have been mentioned. As you know capacitors store charge therefore are capable of electric shock, especially when you reach towards CRT circuitry which have thousands of stored volts in them. Hence why you should be VERY CAREFUL with the insides of a TV.

Also merely putting a piece of metal across the terminal not only allows you to be shocked if your not protected, but a violent discharge to occur. Resistive loading would be much better, e.g. a voltmeter or a resistor.

Also be aware of chemicals sometimes used in products too.

If you're working with microcircuits (e.g. inside your computer) and intend to put it back together working again, be aware of ESD. A quick finger on a component can actually completely destroy the chips on the boards.

 

[DaveC426913]

Are you suggesting that telling someone new to experimenting with electrical items to unplug the device for their own safety is akin to doing something that would be harmful?

No, I'm suggesting that merely unplugging a device from an outlet does not ensure it is safe.

Especially when you go on to prematurely suggest that it won't contain any DC current (apparently, the reason being that it was AC at the outlet). Making DC current out of AC current is as simple as a diode and a capacitor. And a capacitor is the very thing that stores electricity when the device is unplugged.

Try fooling with an unplugged TV and you will blow your brains out with 30,000 volts. Try a disposable camera (that's powered by itty bitty penlight batteries) and you will give yourself burns.

 

[DaveC426913]

If you're working with microcircuits (e.g. inside your computer) and intend to put it back together working again, be aware of ESD.

I imagine those who need to be advised to avoid it probably don't know what 'ESD' is.

(That'd be electro-static discharge.)

 

[Delta]

I imagine those who need to be advised to avoid it probably don't know what 'ESD' is.

(That'd be electro-static discharge.)

Apologies, its just that its so common place at work everyone knows about it.

For those who didn't know, ESD does indeed stand for electro-static discharge. It's the same as the electric shock you can sometimes get off a trolley when you walk around the supermarket. Although for us its a bit of a shock, for ESD sensitive devices (such as microchips) its a killer, and only needs to be much much less.

Just by sitting down and moving around we can create 100's of volts, and when the humidity goes down below 25% (which is why ESD environments need humidity and temperature controls) this can reached thousands, again sitting down. We won't feel it, but it will destroy the device.

That's why its important to keep fingers away from Printed Circuit Boards like in your PC. It's aways best practice to plug the computer in, BUT UNPOWERED, so that it's earthed and keep a hand on the chassis.

 

[Averagesupernova]

Try fooling with an unplugged TV and you will blow your brains out with 30,000 volts. Try a disposable camera (that's powered by itty bitty penlight batteries) and you will give yourself burns.

The most dangerous voltage in a TV set is the 120 volt line. The second anode is 30,000 volts with very little current capability. The second anode voltage is certainly not as uncomfortable as an electic fence or voltage on a spark plug. The biggest danger when working in TV sets is ripping your arm up on the chassis when your reflexes cause you to quickly pull your arm out of the set. I've been shocked by the second anonde and collector on the horizontal output transistor and all that happened was I taught a few people around me some new words. Well, knowing those people, probably not.

 

[DaveC426913]

discharge. It's the same as the electric shock you can sometimes get off a trolley...

(That'd be "shopping cart".)

Trolleys are indigenous to San Francisco.

:)

 

[Cliff_J]

Dave your comments seem quite out of place when there are other posts that warn of the hazards in a charged capacitor.

 

[karen03grae]

Hello,

Tonight I will commence the dissection of my old cell phone. But first a few words for the phone:
It was a faithful phone. Never loud or obnoxious. Always had full signal strenght. And that blue backlight...
Okay, ready to dissect. It's amazing how 4 years with a cell phone can change the way you think of it. Anyways...so there shouldn't be any shock risks involved right? Cell phones should have capacitors in order to create EM waves right? Well, I should be able to put pictures of the phone dissected on here. We'll see.

 

[karen03grae]

Here are the results. This is just a preview.

 

[karen03grae]

and the other two pictures...

 

[faust9]

The "what's that" is the vibrator. There is a little motor that is out of balance inside that little battery-like case. If you were to cut the little wires and connect then to a AA or AAA battery then the motor would start to vibrate.

Your previous picture of the bottome side circuit:
If I were a betting man then I'd say the thing under the white sticker is the main processor. The square chip---about 5mm by 5mm---to the right of that is the transceiver(transmitter and receiver in one chip). Notice how is has a square of foil around it. That's probably a ground plane which helps isolate the transceiver signals from the rest of the circuit.

A lot of those little 1mmx1.5mm black/brown/gray chips a resistors and capacitors and/or diodes. See the big yellow thing that says Hitachi? The yellow thing with the red line above is a capacitor. There is a smaller one like it in the center of the photo as well.

The thing that says Hitachi is a power amplifier. Exactly what its purpose in the circuit is hard to say without a much closer look. It suffices to say that it takes a small signal of some sort and makes it much larger.

The thing under the sticker could be the transceiver and the processor could be the smaller chip to the right. I'd need a closer look to tell what is what.

It's amazing how much stuff is hidden inside of a little cell phone huh?

 

[karen03grae]

IT WORKED! It really worked. I severed the vibrator wires from their initial source and then used a nail clipper to remove some of the outer covering. Then I had to use foil for extensions...but when I connected it to a AA it WORKED!

Ha! I'm so easily amused! So you say the yellow thing w/red line is a capacitor? Any ideas for a project with that?

 

[Phaedrus]

wow...something I can actually respond to with some knowledge.
In my childhood broken hairdryers were subjected to my curiosity. I found that almost every time what was wrong was that the thermostat was stuck. Usually from overheating due to hair and dust collecting on the screen. The thermostat will look like a little piece of metal with a contact on it...usually located near or where the heat is generated. I also found that the little fan can be disconnected and run by itself on a DC battery...it just doesn't run as strong. I agree though that one should not plug it back into an AC outlet once it has been dissasembled...however simply cleaning off the screen and then smacking it on the counter a little sometimes can cause the thermostat to become unstuck...sometimes you can see it from the outside through the air hole and use a nonmettalic item to reach in there and loosen it.

 

[Math Is Hard]

So what makes a blow-dryer "blow" anyway? I don't have clue. How does the air get sucked in on one end and forced out on the other?

 

[brewnog]

MIH.

A hairdryer is simply a fan inside a tube. The fan sucks air in at the back, blows it over a heating element, and spits it out at the front. Think of an office fan, or an aeroplane propeller.

 

[FredGarvin]

Usually they are cage fans similar to most bathroom celing fans. There is usually a side mesh that is the air intake. If you place your hand over the inlet (don't do it for very long or it will over heat) you should hear the electric motor speed up, just like a vacuum cleaner.

 

[FredGarvin]

Ha! I'm so easily amused! So you say the yellow thing w/red line is a capacitor? Any ideas for a project with that?

Not that I'd recommend it, but I used to work with some EE's that would play jokes on each other by plugging in capacitors to a wall outlet under each others' desks and wait for the thing to explode.

 

[Math Is Hard]

Ack! Sorry for dumb question. I guess it's just how powerful the suction is at the vents that made the think there was something more elaborate going on. And yeah, I sure do hear the motor speed up when I put my hand over the vents (or when I get my hair caught in them!)

 

[FredGarvin]

There's no such thing as a stupid question...well maybe one or two out there are, but yours wasn't.