100 volt AC machine plugged into 220 Volt AC supply in error

Thread Starter

David HK

Joined Jun 20, 2013
8
Perhaps some kind person can help me.

A Japanese made handheld massager was plugged into a 220 volt AC supply in error. I have managed to open the casing and look at the circuit. I found that a thermal fuse had failed and therefore replaced it with a very similar value. Tested it on a 110 volt AC supply and the thermal fuse failed again.

I disconnected one of the AC supply leads to bypass a small circuit and the machine worked in slow and high speed. The fault therefore lies in the small electronic circuit. I have hand drawn the circuit and my guess is that the choke/inductor may have failed, but I am not sure.

Can anyone offer a point of view please.
 

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Thread Starter

David HK

Joined Jun 20, 2013
8
If it is intended to be variable is there more to it than shown?
Max.
Thank you for the reply.

The circuit is very simple and the photograph shows all the components illustrated in my hand drawn circuit sketch.

The only item not in the photograph which appears to be working fine is the motor.

David
 

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MisterBill2

Joined Jan 23, 2018
18,169
Thank you for the reply.

The circuit is very simple and the photograph shows all the components illustrated in my hand drawn circuit sketch.

The only item not in the photograph which appears to be working fine is the motor.

David
The board marking for the black object calls it "F1", indicating that it is a fuse of some rating. At least that is my guess based on what is shown in that picture. So you will need to read the marking on that device and replace it with another of similar rating. But since there is already a fuse, it seems that there must be more than what we see in the picture. I only see a very small bit of the switch and the associated wires.
So all conclusions are guesses until all of the information is provided.
 

Tonyr1084

Joined Sep 24, 2015
7,852
This may or may not have any bearing on this discussion but years ago I had an experience with a thermal fuse. My mistake was soldering it to the wires it was connected to and not crimping it. The result of soldering the thermal fuse - more appropriately called a "Fusible Link", caused it to fail before power was applied. I had to put another in its place and NOT solder it - but rather, crimp connect it.

Could it be possible you blew the link when you soldered it? Rather than bypassing the entire circuit board, bypass (temporarily) the Fusible Link. FL's are designed to blow when excess heat is detected. Depending on their rating they respond at different temperatures. They can also serve as a fuse because excess current will also overheat them and cause them to blow. However, I wouldn't depend on a FL to protect a circuit.

The circuit in your photograph consists of some very basic components. Highly unlikely they would be the problem - aside from the possible FL failure. Is that a black thing under the resistor? Is THAT the FL? Makes sense that if there's a failure of the motor that the resistor would heat up and cause the FL to blow. I doubt the coil is having any issue - though it's not possible to completely rule that out. Also, if you could include a picture of the back side of the board, that might clear up some issues as well. After all, it IS possible you may have burned a trace off the board. I've seen that before.
 

MisterBill2

Joined Jan 23, 2018
18,169
If the legend on that black object is indeed "FL" then it may be a filter choke, in which case it can be bypassed, although that will make the device produce more radio frequency noise. The motor may be a brush type motor that would benefit from the noise filter. Can we have a bigger photo that shows the motor as well?
 

Thread Starter

David HK

Joined Jun 20, 2013
8
Dick,

Thank you very much for your reply. I will follow that up tomorrow as it is now early evening time here in Hong Kong and darkness heralds.

I will also add some more photographs, and can confirm that the underside of the PCB is in pristine condition.

I was unaware that an inductor could fail, so I will try your test. For clarity could you please confirm that it should be open and able to pass voltage to indicate that it works as expected. I have tested it with an AVO meter for continuity and receive ding from the AVO meter which would indicate that it is in working order. But I might be wrong.

Although I am 71 years old and , more of an amateur mechanical engineer, my electronic prowess probably equates to that of an 18 year old who has received electronics tuition at school.

But, thank you for your contribution..


David
 

MisterBill2

Joined Jan 23, 2018
18,169
I am wondering now about the mechanism of how a 100 volt appliance became connected to 220 volt mains. I am aware that in mainland China the standards voltage is 220, but not sure about Hong Kong.
 

DickCappels

Joined Aug 21, 2008
10,153
Like most of the civilized world, residential and office mains are 220V @ 50 Hz. Lost a 120V electric shaver that way when I forgot to use the step-down transformer.

The inductor should show a very low resistance if it is ok. By the way, I know that in some places, when it is said that (for example) a light switch is open, that means that the light has been opened and is on. In my experience, when talking about circuits "open" usually means "open circuit" - no current flows. "Closed" means the opposite. I was confused when walking into a darkened room and my friend said "open the light".

If the inductor is damaged damaged, you probably won't get a reading or an over-range reading, depending on the type of meter you use since there is nothing in the circuit that is in parallel with it. Incidentally, Is the inductor the solenoid that vibrates?
 

Thread Starter

David HK

Joined Jun 20, 2013
8
Hong Kong was formerly a British colony until 1997 when sovereignty was changed from the United Kingdom to China.

Regardless of that, the present voltage system is 220 volts AC. I have touched it a few times very inadvertently. And survived!
 

Thread Starter

David HK

Joined Jun 20, 2013
8
Hong Kong was formerly a British colony until 1997 when sovereignty was changed from the United Kingdom to China.

Regardless of that, the present voltage system is 220 volts AC. I have touched it a few times very inadvertently. And survived!

I forgot to mention that the 'plug in' was done in a moment of adult old age stupidity!
 

Tonyr1084

Joined Sep 24, 2015
7,852
I forgot to mention that the 'plug in' was done in a moment of adult old age stupidity!
Well then I must be VERY VERY old. Back when I thought I was very young - say 7 years old, I learned what it felt like when plugging a difficult to plug in plug was being pushed into an outlet and my fingers slipped off the plug body and touched the electrical portion of the plug. How my arm rang out with the power flowing through my hand. So old age doesn't mean stupidity. We've all, at various ages touched mains power, be it 120 VAC in my case - or 240 VAC in your case. And the truth is - we all make mistakes. You're definitely not alone on that one.
 

Phil-S

Joined Dec 4, 2015
238
As it's such a simple board, have you tried unsoldering one end of each component and putting a meter across the isolated components?
I'm guessing that the switch and diode are for two speed operation.
If it is a 1N4001, then that might have been zapped. The 1N4001 is the lowest rated diode of the series. That might be open circuit. Check it on the diode setting of the meter and note the reading, then reverse the meter leads and check again
I would replace it with something beefier like a 1N5403 that is rated for at least 200-V, if it's the culprit
 

Phil-S

Joined Dec 4, 2015
238
Well then I must be VERY VERY old. Back when I thought I was very young - say 7 years old, I learned what it felt like when plugging a difficult to plug in plug was being pushed into an outlet and my fingers slipped off the plug body and touched the electrical portion of the plug. How my arm rang out with the power flowing through my hand. So old age doesn't mean stupidity. We've all, at various ages touched mains power, be it 120 VAC in my case - or 240 VAC in your case. And the truth is - we all make mistakes. You're definitely not alone on that one.
240-V AC hurts, a lot. If you want to know what it might feel like to have your arm pulled off, 240-V is the way to go
 

Tonyr1084

Joined Sep 24, 2015
7,852
240-V AC hurts, a lot. If you want to know what it might feel like to have your arm pulled off, 240-V is the way to go
I can't imagine. I don't WANT to imagine. So I'll trust you - it hurts like hell. However, I HAVE been hit by 65KV discharge from an old TV console CRT. In the chin no less! Ho-lee phuck!
 

MisterBill2

Joined Jan 23, 2018
18,169
I believe that the drawing of the circuit shows every element in series, thus there is no reason to unsolder anything, except for replacing it, And the TS already stated that the device worked with that one item bypassed, at least I think that is what the TS stated.
 

Thread Starter

David HK

Joined Jun 20, 2013
8
Tony r,

You make a valuable point about the the possible effect a hot soldering iron may have on a fusible link.

The Lunar New Year is still being celebrated here in Hong Kong and once normality resumes I shall purchase some more fusible links and try the circuit again. Its interesting to note that when I purchase these items they come with very long wire legs.

It may take a week or more to send a reply on this interesting point.

By the way: What do the letters TS stand for in comments text?


David HK
 

MisterBill2

Joined Jan 23, 2018
18,169
TS stands for "Thread Starter", the originator of the thread.
And the long leads on the thermal links are intended to prevent soldering from damaging the link, by keeping soldering heat far away.
 
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