Even with the long leads - I managed to blow a Fusible Link before putting it to use.

OK, I have not replaced them, I just bypass them and make sure that there is a correctly sized fuse in the device. My reasoning is that either the device is OK and the trip was a nuisance trip, or it has started failing and soon will draw enough current to pop the fuse. My experience so far is that they were all nuisance trip events.

 

@MisterBill2 I've had some nuisance trips before too. Mother-in-law bought a washing machine. Given her age she doesn't do a whole lot of laundry. Don't ask! She hardly used her machine and within one year of purchase it failed. The failure was in the "Mode Shift Coil". It was a nice machine with self diagnostics. She called a repairman who explained that the MSC was not available, that she would have to purchase the entire mechanism at a cost of $138.00 (US) and an additional $300 for the repairman to tear out the old and put in the new. So she decided she'd just go with a new machine again. I stopped her and asked if I could have a look at it, thinking maybe the repairman was handing her aline, given her age and gender. So I called around but found exactly what was being told her, that she'd need an entire new unit. It was then that I decided to pull the coil off. Two screws and it was out. Cracked open the case and the coil was pristine - no signs of overheating or a short. The FL was rated for 106% of normal operation. In other words, it was designed to fail. Went to Radio Shack and for less than $2.00 I got a link that was rated for 144% normal operation. That was several years ago and the machine is still working.

150% is typical engineering for life critical applications. 133% is common for high quality commercial equipment. 106% (in my opinion) is good for children's toys. Even cheap fans have FL's that are rated for 133% normal operation. So that machine was deliberately designed to work for a short period of time, then require the resale of the ENTIRE GUTS. Since the MSC was easily removed with just two screws and a plug - it would extremely easy to just sell a new coil. But where's the profit in that?

 

@MisterBill2 I've had some nuisance trips before too. Mother-in-law bought a washing machine. Given her age she doesn't do a whole lot of laundry. Don't ask! She hardly used her machine and within one year of purchase it failed. The failure was in the "Mode Shift Coil". It was a nice machine with self diagnostics. She called a repairman who explained that the MSC was not available, that she would have to purchase the entire mechanism at a cost of $138.00 (US) and an additional $300 for the repairman to tear out the old and put in the new. So she decided she'd just go with a new machine again. I stopped her and asked if I could have a look at it, thinking maybe the repairman was handing her aline, given her age and gender. So I called around but found exactly what was being told her, that she'd need an entire new unit. It was then that I decided to pull the coil off. Two screws and it was out. Cracked open the case and the coil was pristine - no signs of overheating or a short. The FL was rated for 106% of normal operation. In other words, it was designed to fail. Went to Radio Shack and for less than $2.00 I got a link that was rated for 144% normal operation. That was several years ago and the machine is still working.

150% is typical engineering for life critical applications. 133% is common for high quality commercial equipment. 106% (in my opinion) is good for children's toys. Even cheap fans have FL's that are rated for 133% normal operation. So that machine was deliberately designed to work for a short period of time, then require the resale of the ENTIRE GUTS. Since the MSC was easily removed with just two screws and a plug - it would extremely easy to just sell a new coil. But where's the profit in that?

That sounds a bit like the new computer washing machine that I fixed. A clients friend had here machine stop working and the repair guy said $350 FOR A REPLACEMENT COMPUTER MODULE. So I was asked to take a look. I opened the back of the top console and read the service instructions and went through the reset/reboot sequence, then unplugged it for a few minutes. Plugged it back in and it worked. My reputation among that group is very good. And it saved the lady about $475. (Labor +parts) It seems that not only am I more skilled, but also far more honest than some repair folks.

 

It seems that not only am I more skilled, but also far more honest than some repair folks.

Lets face it, you have 'Magic Fingers!'
The old 'Loose Connector Trick'!
(Maxwell Smart)
Max.

 

Lets face it, you have 'Magic Fingers!'
The old 'Loose Connector Trick'!
(Maxwell Smart)
Max.

That time it was NOT a loose connector. That would be the call I got from a lady whose flat screen monitior just all at once went black. She was complaining that it was "the hard drive" that failed, which is what she called that big box sitting on the floor. Then she was complaining about why was I looking behind things when the problem was the monitor. I picked up the end of the power cord that had fallen out and dropped to the floor, and plugged it back into the monitor. She had no clue that a monitor needed a power cord. But that did fix the problem. There should be a license based on technical understanding required before folks can own a computer.

 

Here is an enlarged photograph for reference.

One point I failed to mention. After opening the case I found the Fusible Link was horizontal and under the resistor. There was also heat dissipation compound between the upper side of the fusible link and the underside of the resistor. That must have been put there for a reason. In the photograph below I installed a replacement fusible link vertically to ascertain what might happen in this position - it failed.

On balance, I think Tonyr is close to the mark about soldering iron heat so I am preparing a series of step by step tests as I install a new fusible link.

David HK

 

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.

You might look a bit closer at the diode; it may well be a 1N4007 rather than a 1N4001. It seems pretty clear that the thermal fuse was intended to open the circuit if the 22Ω resistor got too hot (e.g. from too much motor load); if not thermally connected to the resistor, the thermal fuse may not have a useful function.

 

Your comment noted, and a fair point.

However when I jumped the power supply (cutting out the small circuit board) to the switch and motor everything ran fine. The switch has three positions - High - OFF - Low speed. The diode is across the low speed selection and the difference between Low and High speed function can easily be seen. I'm fairly sure the diode is good.

Continuity tests are good and working except for the fusible link.

The only thing I can do at the moment is to wait for the shops to reopen after the Lunar New Year and then purchase more fusible links. I will keep the thread updated as things happen.

Thank you.

David HK

 

OK. so here appears to have been deliberate coupling between the 11 ohm resistor and the thermal link. That is very interesting. Perhaps the intention is to limit the maximum run time of the device, which is a rather sneaky thing. Is there any chance of getting a small thermostat that could replace the thermal fuse, but reset after the thing had cooled?
It appears that since the thermal fuse is well away from the motor, which is the heat generating part of the device, that the intention of the resistor/thermal fuse device was to duplicate the temperature rise in the motor and avoid a burnout possibility. So there is a time-limit built in, is the appearance. So my guess is that this device is a "Hitachi" brand massager. It appears to have a brush type of motor with wound fields, since a permanent magnet motor would not run on AC power. So if you assemble it without that thermal coupling you may possibly have an overheating problem if you run it at high speed for too long. But what is "too long" is an unknown quantity.

 

I don't know this for a fact, but I imagine a FL that gets warm and cools repeatedly without blowing may weaken over time and its breaking point become derated. Said another way - the link may be rated for (oh, let's say) 100˚F. Over time with use its break point may become 95˚, then 90… and so on. Eventually it will fail. Keep in mind I chose 100 degrees at random for sake of making the point.

not only am I more skilled, but also far more honest than some repair folks.

Face it - a washing machine repair man is probably NOT a skilled computer technician. He (gender for reference only - nothing against women) might not even know that he has to shut down his own computer periodically. Even my iMac computers occasionally need to be shut down and restarted.

My furnace went on the fritz. It's a 97% efficiency unit. The wife wanted to call a repair man. I just shut the main power to the furnace off, waited a minute then turned it back on. It's been running fine ever since. AND between that time and now there have been at least two power failures. One that was probably an accidental loss of power and the other was a scheduled line upgrade where power was off for about 12 hours.

The wife's phone (Samsung) would sometimes need to be restarted. My iPhone needed it at least once in the years I've had it. Face it - computers sometimes get confused as to where they are and need to start over. I doubt a washing machine person would readily know this. With my furnace, I chanced that restarting it would work. So now every year during the off season (not heating) I shut it off. No need to run power through it all that time when it's just sitting idle, doing nothing.

Back to this thread - - - That looks like a hair dryer. Don't know if I missed a statement to that fact. Perhaps you can take a picture of the underside of the board and post that as well. Seeing the circuitry may give us a better idea of what they're doing with the electronics. Some of the cheap hair dryers I've pulled apart had the switch and the diode and nothing else. @MisterBill2 may be onto something with the manufacturer being sneaky and creating a deliberate failure point. Then again, maybe it's a code requirement in the country of origin.

 

I don't know this for a fact, but I imagine a FL that gets warm and cools repeatedly without blowing may weaken over time and its breaking point become derated. Said another way - the link may be rated for (oh, let's say) 100˚F. Over time with use its break point may become 95˚, then 90… and so on. Eventually it will fail. Keep in mind I chose 100 degrees at random for sake of making the point.

Face it - a washing machine repair man is probably NOT a skilled computer technician. He (gender for reference only - nothing against women) might not even know that he has to shut down his own computer periodically. Even my iMac computers occasionally need to be shut down and restarted.

My furnace went on the fritz. It's a 97% efficiency unit. The wife wanted to call a repair man. I just shut the main power to the furnace off, waited a minute then turned it back on. It's been running fine ever since. AND between that time and now there have been at least two power failures. One that was probably an accidental loss of power and the other was a scheduled line upgrade where power was off for about 12 hours.

The wife's phone (Samsung) would sometimes need to be restarted. My iPhone needed it at least once in the years I've had it. Face it - computers sometimes get confused as to where they are and need to start over. I doubt a washing machine person would readily know this. With my furnace, I chanced that restarting it would work. So now every year during the off season (not heating) I shut it off. No need to run power through it all that time when it's just sitting idle, doing nothing.

Back to this thread - - - That looks like a hair dryer. Don't know if I missed a statement to that fact. Perhaps you can take a picture of the underside of the board and post that as well. Seeing the circuitry may give us a better idea of what they're doing with the electronics. Some of the cheap hair dryers I've pulled apart had the switch and the diode and nothing else. @MisterBill2 may be onto something with the manufacturer being sneaky and creating a deliberate failure point. Then again, maybe it's a code requirement in the country of origin.

The hair dryers that I have seen all run at least some of the air over and through the motor for cooling. This device does not appear to do that. In Addition, the TS called it a "Massager" at the start of this thread. Thus hair dryer considerations do not apply here.

 

OK