Hello.

I have here a home appliance. It's a portable hoover. Not sure this is the correct name for the following appliance:


The problem with it is that all of a sudden, we couldn't stop the appliance. It was working even when we turned it off on the switch (3 states switch).
So, I disassembled and found a floating wire (black wire) and I soldered it to where it should be.
I'll share a few links with pictures I took from the "thing" this black wire should be connected to.

https://i.ibb.co/r5dCjzh/20220123-203932.jpg (this "thing" connects here in the PCB)
https://i.ibb.co/4V268nz/20220123-203839.jpg
https://i.ibb.co/ZfQh9k9/20220123-203902.jpg
https://i.ibb.co/k0FkLct/20220123-203635.jpg
https://i.ibb.co/6YBDC9q/20220123-203816.jpg
https://i.ibb.co/0fkmp03/20220123-203701.jpg
https://i.ibb.co/85NZVC3/20220123-203805.jpg

I have no idea what this is, but this is not accessible from the outside of the appliance. It was inside the case. I can only think this may be some sort of protection, because the metal plate of the red wire seems to be some sort of magnetic switch, as it is in a V shape and it's making contact with the plate of the black wire.
I'll try to represent what I see. If the '|' is the black wire plate and these 2 representations are the metal plate of the red wire "\ |" and " ||", they can combine themselves as position 1: |\ | and position 2 | || . Not sure you guys know what I mean.

Anyway, the reason I created this post is because, sometimes when I connect the charger to the appliance, the motor inside seems to want to start spinning, but it doesn't and it keeps doing this weird sound as if it is trying to start spinning. Other times, I connect the charger and nothing happens but a red led lighting up telling it's in charge mode.

When I connect the charger to the appliance and the motor tries to spin, I can feel at least one component going quite hot, so there is a short either in this component or somewhere else. But this only happens if the motor tries to spin.
The component shows only this reference: 4403 CT7A2 and I couldn't find anything like this.

I have a pic too:


I have removed this component and soldered it back to place, just in case it could be some pin shorted. But no luck.
I might also have to ask help with the switch because it may also be not in the best conditions, but that will be for later, if I have luck with this component!

 

That looks for all the world like a 3.5mm phone jack. Is is mounted somewhere?

 

yup, mono jack.
the last one is SOIC8 package but do not recognize the logo or marking... can you not post image of the product on PCB so we can see the surrounding parts too?

 

@Yaakov and @panic mode I'll take a couple more pictures later today, after work.

Thanks

 

4403 is a N channel MOSFET
https://www.tme.eu/Document/62da0b5af763fd84d7fd7f4cc011472f/AO4403-DTE.pdf

 

Here are some more pictures:
https://i.ibb.co/J2YnPhR/20220124-191855.jpg
https://i.ibb.co/F5XB0pr/20220124-191847.jpg

An thank you @Jony130 for identifying that component!

 

4403 is a N channel MOSFET
https://www.tme.eu/Document/62da0b5af763fd84d7fd7f4cc011472f/AO4403-DTE.pdf

I think you meant P channel mosfet, btw!

 

You guys can help me finding some equivalent mosfet models in case the shop where I use to go don't have this specific mosfet?

 

Ok, I got hands on an equivalent MOSFET (AO4435) to the one in question and I'm going to replace it. The original one was heating up too much when I put the appliance to charge. So, I hope it's reasonable to assume that this MOSFET would be in short!

Now, just to make sure, is it safe to assume that the marked pin in the below image is where the IC pin 1 should be? Or is it the one on the right side of that same row?

 

With the notch and little white circle, that is pin 1.
Check the PCB traces to make sure they match what the MOSFET pinouts are, regardless....

 

With the notch and little white circle, that is pin 1.
Check the PCB traces to make sure they match what the MOSFET pinouts are, regardless....

Yeah, according to the tracks, that row has 3 source pins and one gate. The upper row has all the 4 drain pins as the datasheet shows.

I replaced the MOSFET but the behaviour is still the same.
I took some pictures of this board. Maybe someone have a clue of what else I can test/measure to try to sort the problem out.
I tried the motor out of the circuit, using my PSU. Despite the fact that my PSU can't deliver the required current, the motor works (by dropping the PSU voltage).

What else can I do?
https://i.ibb.co/r5sKKYM/20220131-173145.jpg
https://i.ibb.co/S6RhyhF/20220131-173223.jpg
https://i.ibb.co/jkZG4f3/20220131-173207.jpg

 

It appears that Q1 drives the 8 pin Q2 via R37 (a guess). Check Q1, for if it is bad, it may be turning on the gate of Q2 100%.
Also, your Q3 looks like it has been running hot on that board. I would check that device as well.

 

It appears that Q1 drives the 8 pin Q2 via R37 (a guess). Check Q1, for if it is bad, it may be turning on the gate of Q2 100%.
Also, your Q3 looks like it has been running hot on that board. I would check that device as well.

How are you counting pins?

2 4 6 8
⊃
1 3 5 7
or
5 6 7 8
⊃
1 2 3 4

I assume one of the ways above. But by what I can see from the screen where I have removed the MOSFET, it seems R37 goes to the gate of the MOSFET, at pin 7 or 4 in the representations above.

Edit;
So, I can confirm that Q2 pin drives/is connected to MOSFET pin 7 (or 4) via R37 (2kΩ resistor)

Edit 1;
Can this component be identified?

It's the mentioned Q1

 

Pins are always
5 6 7 8
⊃
1 2 3 4

on IC and devices that use IC layouts, such as this MOSFET. Pin 4 would be the gate.

Can't identify the NA or D? device. If D8, would be one thing, DB would be another...

 

Pins are always
5 6 7 8
⊃
1 2 3 4

on IC and devices that use IC layouts, such as this MOSFET. Pin 4 would be the gate.

Can't identify the NA or D? device. If D8, would be one thing, DB would be another...

I can't tell for sure either. This is the best I can get from the usb microscope!

 

Error in the pins, it is: (my mistake)
8 7 6 5
⊃
1 2 3 4

Always count counter-clockwise. I didn't look carefully at your arrangement once I saw the 1234 in the right order. However, for this MOSFET, the order of 5 to 8 does not matter, they are all tied together.

 

Error in the pins, it is: (my mistake)
8 7 6 5
⊃
1 2 3 4

Always count counter-clockwise. I didn't look carefully at your arrangement once I saw the 1234 in the right order. However, for this MOSFET, the order of 5 to 8 does not matter, they are all tied together.

I was about to swear that I have seen different pin displacement. Anyway, how can I check if 3 Qs are good or not?

 

Only way to test them is to remove them from the board and test with any common component tester. Those testers are cheap and can be found on sites like Ebay or Amazon.
You could test some transistors with a DMM, in diode test mode, to test the junctions of regular transistors. There are ways to test some MOSFETs, check youtube videos....

 

Only way to test them is to remove them from the board and test with any common component tester. Those testers are cheap and can be found on sites like Ebay or Amazon.
You could test some transistors with a DMM, in diode test mode, to test the junctions of regular transistors. There are ways to test some MOSFETs, check youtube videos....

Those ebay/Amazon testers are mostly for 3 pin components. At least that SOIC8 can't be tested there unless I solder 3 wires to it and give it a try. Same for the other ones. But I can do that, for sure!

 

Those ebay/Amazon testers are mostly for 3 pin components. At least that SOIC8 can't be tested there unless I solder 3 wires to it and give it a try. Same for the other ones. But I can do that, for sure!

The pins on the 8 pin device are connected internally, so in effect it is a 3 active pin device. No need to solder wires to it. Just test between any pin 1-3, pin 4, and any pin 5-8