My own suspicion is that either one of the three components on the power board above might be damaged:
- X2 capacitor (yellow)
- BTA10 Triac (black, ST brand)
- 5V DC relay (Omron brand)
I am not formally trained in electronics so I have limited understanding of how these components work. My guess was solely based on my personal repair experience where I have successfully fixed a few dead devices/ appliances by simply replacing components of similar nature to these components above.
To determine if an electronic component is faulty, it would require removing the component from the board to measure its electrical properties with the multimeter. Taking measurements while it is still electrically connected to the board will not provide any certainty of whether it is good or bad. And removing a component from the board could be tricky as it usually requires desoldering it from the board, which could introduce unintended damage to nearby components (or even the component itself) if not done properly. I wanted to have more certainty that a component was likely damaged before resorting to removing it to check. Also, because if the removed component turned out to be good, there is the hassle of having to solder it properly back onto the board, which could again be tricky business. For these reasons, I decided I should seek advise from other experience repairers in my community before proceeding further.
I received the following four suggestions/guesses from several active members in the Repair Kopitiam community when I posted a message of my issue to them. Other than guess #4, I did not expect the others to point me back to areas that are not on the power electronics board. I also did not really think these were likely causes, but I proceeded to investigate them anyway.
The rationale behind this guess is that if there was some kind of braking device to stop the motor when powering it off, and that device was damaged, then the unexpected back EMF (ElectroMotive Force) could be triggering the power trip. So I carefully checked the structure of the motor and didn't find anything that looked like a brake on the motor. The only thing other than the motor's terminal that is connected to the circuit board was a small black component tucked under the motor's cooling fan blade. It was held in place by magnet forces and there is no label on it that can help me identity what it is for.
To determine if this component could have anything to do with the power trip issue, I detached it from its location on the motor then operated the blender. Here is the result -
The EMI filter referred to here is the large metal box component that I checked for electrical continuity in Part One. I was only concerned with its electrical pass-thru (continuity) at the time as I was diagnosing for any breakpoints that could have prevented the blender from powering up. Now that it could power up, there might just be a possibility that the capacitors or inductors inside the EMI filter are faulty without affecting its ability to send power to the board. This is because most of the components in the EMI filter are connected in parallel to the power supply wires. as shown by the circuit diagram at the bottom of its label. So power could still be sent thru if any component connected in parallel was damaged.
If this was the case, its inability to properly filter the back EMF as the motor spins down to a stop could be a reason for triggering the power trip. The multimeter that I have is only able to measure capacitance and resistance, but not inductance. I measured both capacitance and resistance between the top and bottom lines and found that both values are very close to the specifications stated on the label.
So I concluded that the EMI filter is in good working condition.
I hooked up the connector of the motor directly to the AC output from the EMI filter using two short pieces of wire. To prevent the connection from coming off due to strong vibrations from the motor (yes this motor's gonna be quite a beast when it runs at its max rated power of 600W), I used a rubber band to hold the connection assembly in its place like this:
Then with one hand wearing an insulation glove (in case something breaks loose and electrically touches my hand) while holding the uncovered blender steady, I plugged it in and powered the beast up.
Well, the friends who suggested this to me were probably disappointed that nobody got shocked by what happened. :)
On to the last suggestion!
This is suggesting that a capacitor on the power board, likely the yellow X2 or a blue MOV capacitor could be damaged, leading to the board's inability to filter out any back induced EMF when the motor spins on its own to a stop during power off. This was something I had also suspected to be a possible culprit. However, I decided not to investigate any of the capacitors but instead look into the Triac.
The main reason I decided to investigate the Triac (I didn't know that's its name at first) was that the burnt copper trace that I had repaired in Part One was directly linked to one of the pins of the Triac.
But I didn't know how a Triac works, much less how to diagnose if it was damaged. So the next thing I did was to find its datasheet based on the marking on the component: BTA10-600BW.
From the datasheet (https://www.st.com/resource/en/datasheet/btb10.pdf), I extracted this important information from two of the pages.
Then I went researching on how to diagnose a Triac, how a Triac works, and what is meant by a "Snubberless" Triac.
Most of the Youtube videos I could find on diagnosing Triacs have verbal explanations in Hindi, which I cannot understand, haha. Fortunately, I found this one that uses on-screen texts to explain things - https://www.youtube.com/watch?v=VzywtlHry4g. After watching the video, I knew for certain that it is possible to use a multimeter to check if a Triac was damaged based on the conductivity characteristics between the pins. But I wanted to know more about what each pin is for so that I can have a better grasp of what I should be checking for. I searched online for how Triacs work and found this Youtube video to be particularly helpful in understanding the configuration of the 3 pins on Triacs and also what a Snubberless Triac means. https://www.youtube.com/watch?v=9He-d-IdRQY
The next step was to disconnect the Triac from the circuit board. I did not want to totally detach the Triac so that in case the test showed that it was not damaged, I would be able to reattach it back easily. The easiest way I could think of was to snip off the pins of the Triac near their bent locations. This would allow me to reconnect it back easily if necessary, by applying solder to where I had snipped open the pins.
After the pins were snipped, I checked for electrical conductivity between pins A1 & A2. Theoretically, with a good Triac, pins A1 and A2 should not be connected if the gate pin (G) is not triggered. But in the case of this Triac, I found that it was a closed circuit! This must mean that the Triac was damaged! I was eager to get a new Triac to confirm this, but upon checking with the local shops still in business at Sim Lim Tower during the Covid-19 lockdown, they do not have the same Triac I needed, although one of the shops did have the non-Snubberless version (ie. BTA-600 without the BW). It probably was too risky to try it so..
... it was online shopping time! :)
I found and ordered a bunch of BTA-600BW from this seller in China at https://www.aliexpress.com/item/32839985064.html It came in a pack of 5pcs per lot and so each piece was well under S$2. It took only 10 days to arrive, quite fast considering the free shipping and the Covid-19 situation at this time.
When I measured one of the new Triac that I received, between pin A1 and A2, it showed an open circuit as expected. So I was pretty confident this would restore the blender properly and proceeded to swap out the damaged Triac for a new one. This step was much more work than it would seem.
Firstly, I had to drill out the rivet that was securing the damaged Triac and its heatsink to the board.
With the old Triac removed, I could do a simple video below to directly compare how the pins on a good Triac and the damaged Triac behaved when probed with the multimeter set to the mode for testing electrical continuity.
Next, I had to find a bolt and a nut of the suitable size that can secure the new Triac and the heatsink back to the board.
Then I cleaned out the old thermal grease from the heatsink and applied new thermal grease to the back of the Triac.
Just before securing the parts back to the board, I also added a drop of thread-lock to the nut. This was necessary to prevent the vibrations by the powerful motor from slowly loosening the nut over time. It was probably the reason why the manufacturer originally used a rivet to secure the parts together as rivet mounted parts have no chance of being detached by such vibrations.
The new Triac then gets attached and the pins are soldered onto the leftover pins from the old Triac that are still connected to the board.
One final look at everything on the circuit board to ensure nothing was amiss before putting it back to the blender.
Once everything was back the way it was, the moment of truth!
Hooray! Let's try the Pulse mode.
How about the Ice-Crush mode? Hehe.
Finally, I can return the revived blender to its owner, and claim my reward. :P
PS. One thing I noticed here as compared to when it was only partially fixed in Part One, is that the sound of the motor spinning is audibly softer at the slower speed settings, whereas it sounded like it was running at the same speed regardless of whichever speed it was set to in the last video of Part One. This implies that the Triac works to control the speed of this blender. Another precious knowledge that I have learnt from doing this repair. :)
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