Asko Washing Machine (WM-200A) Control Board - missing thermistor (?)

[siers]

Hi All,

Hoping someone here can assist me with determining what part of the control board from an Asko 20005 Washing Machine (Model WM-200A) has gone missing (seems to have broken and fallen out of the machine whilst it was being moved).

The machine still powers on, fills and drains - however when the motor tries to spin the drum it moves maybe half a centimetre and stops.

Looking at the control board (https://photos.app.goo.gl/2ljpzV4QarbzpwVP2), a component on the top right near the connector to the motor is missing (https://photos.app.goo.gl/wlPFCumnvCtCJ0Oq2).

I've found a picture online of a similar control board where the component is still visible (https://photos.app.goo.gl/ZYfTqP4lupMR3skl1) and it originally was a silver coloured disk.

On the circuit board it's labelled as THS1, and I'm presuming it was an thermistor - possibly as an inrush current limiter. I also presume it would be an NTC thermistor, but this is where my knowledge ends on how to confirm if that's correct. I also don't know what value it is either (and I can't see any markings on pictures found on the internet).

I've searched for a diagram/schematic of the washing machine, however I can only find the wiring diagram for the machine itself and not the components on the control board. I've also looked for spares of this board but it's since been discontinued https://www.repairclinic.com/PartDetail/Main-Control-Board/8801138R/1266704?modelNumber=WM200 (the original part number was 8054178 and was since superseded by 8801138).

I did find a used one on eBay in the USA https://www.ebay.com/itm/ASKO-Washer-Main-Control-Board-8801138-USED-PART-/152681180833 and asked the seller if they could see any identification marks on the silver disk - but apparently it's unmarked.

The labels of the machine and motor voltages and values are available here (https://photos.app.goo.gl/pP7XWwtdXaWwYr3j2 and https://photos.app.goo.gl/smpY3Q2VWNsgqioC3).

I'd greatly appreciate any advice on confirming the component and approximate value to use as a replacement.

Thanks,
Jeff.

[jcw0752]

I agree it is probably an inrush thermistor. While I can't tell for sure from your pictures it probably is in series with the motor so that the current that is handled by the triac is limited until the motor comes up to speed. You may have to guess and try by selecting an inrush thermistor that is large enough to handle the motor's current and then stabilizes at a low enough resistance so that it doesn't over heat. These devices do have a limited life span. They are also notorious for having poor or non-existent markings.
John

[siers]

I've estimated the disk in the eBay photo is 15mm across and 5mm thick - would physical measurement provide some form of clue?

[simony]

I too have this washing machine, and have had to repair it with a new board twice over 20 years. It's a good machine which is why we keep fixing it.
The thermistor you speak of does indeed have no markings, it has a resistance of 150-180 ohms when cold, using my somewhat inaccurate analog multimeter.
It is bonded to a Airpax 67L105 thermostat. I tried heating the thermistor but saw no change in resistance, and given that its bonded to a thermostat chip I suspect it is acting as a heating disk of some sort. I can see that the bonding looks like it had been subject to some heating over the years. These measurements were from a spare circuit board that had been swapped out showing the same symptoms that you've described, so maybe the thing was faulty.
The two failures I've had sound exactly like the symptoms you're describing, the machine gives a little click in the drum when it would normally start moving but no movement occurs.
Hope this helps to some degree, although it might be easiest just to buy that one off eBay.
And yes the disk is 4mm deep x 15mm diameter

[siers]

Thanks simony!

I had started calculating an estimated cold resistance at around 30-40ohms (assuming the inrush current would be 3x constant current max of 4amps at 165 volts and for only 0.2 seconds) - so at least it gives me an idea that I'm on the right track.

I might get a few different valued thermistors and start conservatively.

[User32]

FYI, a Asko WM200(A) MCU board does not randomly go kaboom, has the drive belt ever been changed by one with ANTI-STATIC on it?

Or, did it ever gave F6 as a error code? Static electricity tends to build up in the belt and that will cause MCU failure if not replaced by a ESD safe belt. Had the F6 error code on my 20005 and it ended up being a unsafe belt, never had it again after swapping the belt with the ESD safe one.

[Mat_L]

Hi siers

Did you manage solved this? 

I have the exact same issue. However, I still have the round disk that dislodged from the prongs.
If you did solve it, can you let me know the spec for the part...or... do you think it is better to attempt to repair the part (THS1) as I still have the disk that dislodged.

[User32]

Hi siers

Did you manage solved this? 

I have the exact same issue. However, I still have the round disk that dislodged from the prongs.
If you did solve it, can you let me know the spec for the part...or... do you think it is better to attempt to repair the part (THS1) as I still have the disk that dislodged.

Oh hey, are you the guy I was talking to on YT about your 20003 giving F6 when going into spin?

THS1 is a transistor IIRC, I have asked my Asko contact what type it is.

[User32]

Hi siers

Did you manage solved this? 

I have the exact same issue. However, I still have the round disk that dislodged from the prongs.
If you did solve it, can you let me know the spec for the part...or... do you think it is better to attempt to repair the part (THS1) as I still have the disk that dislodged.

Oh hey, are you the guy I was talking to on YT about your 20003 giving F6 when going into spin?

THS1 is a transistor IIRC, I have asked my Asko contact what type it is.

And unfortunately he doesn't know anymore what type it is.

[Mat_L]

Hi siers

FYI, attached is an image of the replacement component that was fitted to my board.  The markings should allow you to get the spec for the component.   

Hope that helps.

[fzabkar]

My searches for "C1412" always turn up PTC devices, not NTC. These are used for short circuit protection. "C1412" is a "type". I don't know whether this is some kind of industry standard, or whether this type also applies to NTC devices.

https://www.tdk-electronics.tdk.com/download/993858/9c123ec2919096c84ebe667ac4ae5d60/protection-devices-onboard-charger-pb.pdf
https://www.mouser.com/datasheet/2/400/PTC_ICL_Leaded_Disks_C1412_C1451_C75-525567.pdf
https://datasheet.octopart.com/B59109J0130A020-EPCOS-datasheet-11797562.pdf
https://static6.arrow.com/aropdfconversion/89c1231e262542c94ed0228ee6b45853d88db102/614protection-devices-onboard-charger-pb.pdf

[Mat_L]

Hi fzabkar

That is way above my grade.  I was posting as a reference for others as I suspect this component may be come an issue for others. As the original is uncoated with age it appears to become easily dislodged - mine occurred when replacing the shocks.

Just a question, would you know how to interpret the spec for the orange ceramic disk capacitor in front of it? Markings are:
2200K
   C

[fzabkar]

That looks like a 2200pF, 10% ceramic cap.

https://www.electronics-notes.com/articles/electronic_components/capacitors/capacitor-codes-markings.php

[Mat_L]

Just for anyone needing this info in the future.  These are 1Kv caps.

If the thermistor dislodges that failure is likely to crack one of the surrounding Capacitors.

[abdulbadii]

usually 3 digit, the last/third is exponent power, in pF unit
IMHO 4 digit follows the same, 2200  to be 220 x 10⁰ i.e. 220 pF

EIA TOLERANCE CAPACITOR MARKING CODE
LTTR CODE   TOLERANCE
Z                +80%, -20% - this is used on electrolytic cap where the minimum value is the major issue
M                ±20%
K                ±10%
J                 ±5%
G                 ±2%
F                 ±1%
D                 ±0.5%
C                 ±0.25%
B                ±0.1%

not so sure final C

[mark346]

The components in question are a PTC thermistor (around 120-150 ohm in room temperature) and a sub-miniature bimetallic thermostat type Airpax 67L100. They are bonded together by a glue which conducts heat . According to my understanding the function of these two components is to prevent the door of the washer from opening during the spinning cycle. When the PTC resistor has a voltage during a washing cycle, it heats up and when it reaches 100 degrees C the thermostat, which is bonded to it, opens (it is normally closed). When the thermostat contact is open the door cannot be opened and at the same time it is giving the control logic permission to spin. If the thermostat is in the connected status, as it is in room temperature, the spinning is not allowed. So the only function of the PTC resistor is to act as a heating element for the thermostat. In my case the Airpax thermostat had come loose from the PTC resistor and the thermostat did not heat up sufficiently to open the contact and to give the permission for spinning. I solved this problem by removing the thermostat altogether and substituting it by an external  switch. When I start the washing cycle I have to turn the switch into no contact position to enable the spinning. After the washing cycle has ended I have to turn the switch back to contact position to be able to open the door.

[Mat_L]

mark346

You are way in advance of me in this.  Thanks for the info.

Quick question - how did you remove the main board from the support frame to work on it? 
I am reticent to go there without knowing how to approach disconnecting the row of connections along the edge of the main board.

[mark346]

Yes, I removed the main board. Without removing the board it is impossible to solder and remove the thermostat. After removing the board I soldered a two pole wire on the thermostat contacts. The wire leads into the switch which is attached outside of the machine on the side panel . If you are wondering about the connectors which are on the main board, they are just normal connectors which you can draw loose. They have a small plastic clip on the side which keeps them tight. You can bend a little that clip and then they come loose easier. You had better to mark the contacts beforehand using a marking pen, then it is easier to put them back. After the connectors are loose you have to take away the small metal clips at the outer edge of the board and then take away the metal clips which hold the transistors against the cooling surface. This latter is the most difficult part but it goes with small pliers and a little force. When you install back these clips you probably have to bend them somewhat back because they were bent when you took them out. On the main board there are also several wires which go to the component which looks like a transformer but I think it is a noise suppressor. These wires have all different colors and the colors are marked on the main board so you can safely take them loose from their pin connectors.

[Mat_L]

That capacitor (in front of the thermistor) dielectric code below- found on the board on another Wm-200 that had components with the full spec printed on them.

2200pF
10%
1Kv
Y5P