Repair a steam iron

[psysc0rpi0n]

Hello.

I own a steam iron that is faulty for the 2nd time.
1st time it was a relay that was replaced by this Omron G5LW-1.

This time I took it to a repair shop and they told me this time the the control board and the iron resistor. They asked me for 125€ for repairing/replacing the parts. This iron cost was of about 220€ (was on a discount, 260€ with no discount) 5 years ago. So I think to pay 125€ now for the repair, is a bit too much.

My attempt now it to try to salvage the board, if possible, by trying to find any damaged components.
So I made a list of the components I can see on the board. However, there are more components I can't see their brand and/or reference/model.
I need some help to know how to check each of these components and what else can I do to try to figure it out!
I'll attach some picture taken with my smartphone. If needed, I'llt ake better pictures with my DSLR.

The list is:

Buck converter based on:
LinkSwitch-TN Family - LNK302/304-306

Three-Terminal Positive Regulator
AS78L05Z-E1

Passive Triac
Z0103 NA 6E532

Relay
Omron G5LE-1 24vc


Board pictures



Edited;
I can't attach pictures. When I try to upload them, I'm redirected to a "Start new post" page and lose my post content. Going to add some links instead.

[fzabkar]

By "iron resistor", do you mean the heating element? If the element is open circuit, or if it has a leak to earth, then a repair would probably be uneconomical.

Otherwise, here are direct links to your photos:

https://i.ibb.co/WvBw7St/20191222-175948.jpg
https://i.ibb.co/84Dc5xD/20191222-180109.jpg

I would measure the output of the LinkSwitch, the input and output of your 3-terminal regulator, and the relay's coil voltage.

Check whether the relay coil is being switched on.

Take care when working with a live PCB.

[psysc0rpi0n]

By "iron resistor", do you mean the heating element? If the element is open circuit, or if it has a leak to earth, then a repair would probably be uneconomical.

Otherwise, here are direct links to your photos:

https://i.ibb.co/WvBw7St/20191222-175948.jpg
https://i.ibb.co/84Dc5xD/20191222-180109.jpg

I would measure the output of the LinkSwitch, the input and output of your 3-terminal regulator, and the relay's coil voltage.

Check whether the relay coil is being switched on.

Take care when working with a live PCB.

Yes, iron resistor I mean the heating element.
Ok, I'll try to do that and be careful because 220V can kill.

I just didn't understand what you meant by (re-)posting the links to my images.

[fzabkar]

The links to your images are not direct links. I was just trying to be helpful by eliminating all the monetising garbage that happens in the background.

[psysc0rpi0n]

Hello again.

With the help of a friend of mine, I was able to confirm that, at least, part of the board of this steam iron is working ok. We could trace most of the expected voltage values from the mains input on the board until the uC. We measured voltages at the input and output of a buck converter, at the input of a 3 terminal voltage regulator and at the input of the uC. So, at least this path is working fine. I hope there's nothing else damaged.

Now what I found out by chance while I was inspecting several other points in the steam unit, was that the heating element of the steam using has 2 fuses. One of them is a thermofuse like this:


and while I was measuring voltages I ended up trying to measure a voltage at this fuse (wrt to mains ground) and when I touched the fuse with the multimeter probe, I noticed a spark and the heating element heated up a little. So, I tried again and kept pressing the fuse's metal plates and the stem heating element heated up as it would normally do.

Now, there are 2 ways this can turn:
1 - I replace the fuse and solve the problem, assuming a peak voltage of my house electrical network blown the fuse
2 - I replace the fuse and the same happens, proving that something else is damaged.

What you guys think I should do?

[CatalinaWOW]

Replacing the fuse is one way to troubleshoot.  It is entirely possible that the fuse was faulty, or blown by a transient condition that did not harm anything else.   But you do need to know if the heating element is damaged or not.  It may have a partial short, pushing the current to just below the fuse blow threshold.  Such a status will lead to uneven heating of the iron (and associated poor performance) and depending on the cause and nature of the short could presage a dangerous condition.

You can get some idea of this by measuring current while it is operating with the replaced fuse.  That current, with the operating voltage, will tell you the power and you can compare that to the rated power on the iron.

If you do conclude that the heating element is bad there may be some less expensive ways to replace it.  In addition to performing an internet search for the part number you might look into other irons from the same manufacturer. Something on the lower end of their features scale might use the same heating plate design and allow you to purchase that for a donor part.

[psysc0rpi0n]

Replacing the fuse is one way to troubleshoot.  It is entirely possible that the fuse was faulty, or blown by a transient condition that did not harm anything else.   But you do need to know if the heating element is damaged or not.  It may have a partial short, pushing the current to just below the fuse blow threshold.  Such a status will lead to uneven heating of the iron (and associated poor performance) and depending on the cause and nature of the short could presage a dangerous condition.

You can get some idea of this by measuring current while it is operating with the replaced fuse.  That current, with the operating voltage, will tell you the power and you can compare that to the rated power on the iron.

If you do conclude that the heating element is bad there may be some less expensive ways to replace it.  In addition to performing an internet search for the part number you might look into other irons from the same manufacturer. Something on the lower end of their features scale might use the same heating plate design and allow you to purchase that for a donor part.

Hi.
Thanks for the help guiding me.
But I'm not sure I follow the suggestion of measuring the current while the appliance operates with the replaced fuse. If the problem is not only the fuse, then if I turn the appliance on, won't the fuse open again way before I can measure any current?

About the other suggestion, I have already tried to search using the numbers I can see on the element but nothing comes up. Actually, the only pictures I can find are from ebay:






This an actual picture of my heating element:
https://drive.google.com/open?id=1EWf1pofoxIiD7zfGtOicO_dR6tCRNVyA
(this is my Google Drive, it's safe)

[CatalinaWOW]

If the fuse opens again with a new fuse you have a hard failure and the heating unit must replaced.  If the current is nominal with the replaced fuse you know that the shop did a lazy diagnosis and your heating element is fine.  But if the wattage is high, but doesn't quite blow the fuse you know the heating element is bad and should be replaced, even if the fuse doesn't blow immediately. 

You can do this test by pigtailing in any fuse of the same rating, though when you put it into service you will have to use something that fits.

[psysc0rpi0n]

Ok. That was an idea I was about to ask if it was doable.
This thermaster fuse is rated at 308°, judging by its reference. So, probably it is prepared to open, let's say at 350° (let's just assume).
Let's also say that the current the steam iron is supposed to work is 10A. And let's also assume that the current needed to open the fuse is 13° (for 350°).The idea was to add a fuse before the Thermaster it, for instance 12A. That way I could check if the heating element is fine without damaging the thermaster again. Is this doable after finding the correct values?

[CatalinaWOW]

I was reading the words and not looking at the pictures.  So now I am a little unclear on what you found.

From the pictures it appears there is a thermostat in series with a thermal fuse.  The thermostat  would be the somewhat rectangular device, while the thermal fuse is the somewhat cylindrical device.  The thermostat does not match the more common configurations for an iron thermostat.  (see the link for some examples https://www.alibaba.com/showroom/steam-iron-thermostat_2.html?spm=a2700.7724857.pagination.1.71712b3696Zq0Q  )

The thermostat opens and closes as the iron temperature passes up and down through it's normal operating point and would normally be the primary temperature control.  The presence of an electronic control board casts some doubt on this, but in my opinion the board is likely to implement a timer function which automatically turns the iron off if it has not moved for a preset time, and possibly other safety/convenience features.  The thermal fuse should remain closed unless the iron goes above a preset safety temperature and then open permanently.  Its purpose is to prevent a fire if the thermostat or other control circuits fail.

The thermal fuse should show near zero ohms.  If it is open it is probably because of another failure which must be found and corrected, though there is some chance that this fuse may be the only failure.

When you said you were probing around the fuse and intermittently could get the iron to heat up what were you probing?  If it was the thermostat it would indicate a failure of this part, but a failure in the open condition which would be unlikely to damage other parts of the iron.  There is some chance to restore temporary operation by cleaning the contacts of the thermostat (the contacts between the bimetal leaves, not the power connections).  As you can see from the alibaba link there is also usually a method to change outside pressure on the leaves to change the operating temperature.  This does not show in your pictures which may indicate a different temperature control approach, or a broken/missing part.

[psysc0rpi0n]

Well, I thought the thermal fuse was the somewhat rectangular device which I posted a picture in post #4.
I thought it would be the thermal fuse because I found this catalog of Thermaster, is I think it is a thermal fuses manufacturer. The last item of this catalog is very similar (maybe with different parameters) and explains how it works. These 2 sheets of metal are tied together with a "drop" of solder which melts if a certain temperature is reached.
Quoting the catalog:

The TF2 is equipped with a solder insert placed in
direct contact with the sensing plate. Upon reaching
the specified temperature, the solder melts, opening
the electrical contacts. Resetting is impossible.

This is an actual picture of this rectangular device which has that tiny thing that looks like the solder I quoted from the link above.
https://drive.google.com/open?id=1El2SL1aeCXdYDYlEofFoGhMxRC24SmcY

Somehow I'm not being able to transfer pictures from my smartphone bluetooth to my laptop, that's why I'm uploading them to Drive. Sorry for any inconvenience.

I was probing this rectangular device and when I placed the probe on top of these 2 metal sheets, they made contact and the heating element heated up. And to make sure we are talking about the same thing, this iron has 2 heating elements. The one on the iron itself and the one we are talking now which heats up the water container to build up pressure and "produce" steam. So, I assumed this was the fuse.

Are you 100% sure this rectangular device is a thermostat instead of a thermofuse? I mean, it makes sense it is  a thermofuse.
The 2 leads of the circular device (you say it's the thermofuse) reads 0.10 ohm.

[JFJ]

... The idea was to add a fuse before the Thermaster it, for instance 12A. That way I could check if the heating element is fine without damaging the thermaster again...

The type of heating element pictured would usually fail in one of two ways. Either, its resistance wire could fracture (go open circuit) or the insulation surrounding the wire could fail - creating a short circuit to the metal sheath that encapsulates the element. As the element heats up (when you close the Thermaster device), it cannot be open circuit. Measuring the resistance between one end of the element and the metal chassis, would determine if there was a short circuit present. So, there's no real need to power the element up to test it.

Thermaster device is a thermal cut-off. It goes open circuit when its sensing plate reaches a specified temperature (set by the melting point of the solder that lies between the plate and the sprung contact). The large surface area of the sensing plate and contact means that the current passing through the device is unlikely to heat it up sufficiently to trip it.

The most likely reason for the thermal cut-off opening is that the fixed temperature bimetallic thermostat, which is also in series with the element, has failed in the closed position (its contacts have welded together). Whenever a thermal cut-off needs to be replaced, the thermostat should be replaced at the same time:

[CatalinaWOW]

I agree with JFJ's analysis.  Appearances can be deceiving.  Thermal fuses are packaged in identical packages to the thermostat in yours.  And I was not familiar with the type of thermal fuse in yours.  The appearance is similar to a thermostat.

[psysc0rpi0n]

Ok, I'll try today follow what was sai here to see if I can find something else about what might be damaged! I'll post updates later...

[psysc0rpi0n]

@JFJ I was trying to understand (exactly) what you said in your last post about the resistance wire to fracture, etc.

Coul you please point out in the same picture you used in your post, what is this wire you're talking about? And also point out the insulation you refer to?
And then, please also let me know exactly what you mean here:

Measuring the resistance between one end of the element and the metal chassis, would determine if there was a short circuit present.

I mean, I understand what you say but I'm afraid of not understanding the exact parts you're referring to. When you say the end of the element and the metal chassis, I'm not 100% sure to what parts you're referring to! I'm sorry, I'm trying to be 100% sure in what I'm trying to do!

Thanks


Edited;
Also, what name can I use to find the circular bimetallic thermostat? I need to purchase one, right?

[psysc0rpi0n]

I can't find the bimetallic thermostats selling to regular customers. Only to retail sellers or whatever they are called. The last email I got, they told me MOQ is 1000 pieces.

Can anyone help me finding someone that sends them to Portugal? Like, I want to purchase maybe 3 for different temperatures.

I'm looking for these ones:
1NT 1/2 Inch Fixed Temperature Thermostat, Open 105C, Close 85C, 1NT01L-8425 (Part #1NT01L-8425)
1NT 1/2 Inch Fixed Temperature Thermostat, Open 110C, Close 90C, 1NT01L-8426
1NT 1/2 Inch Fixed Temperature Thermostat, Open 115C, Close 95C, 1NT01L-8427 (Part #1NT01L-8427)