Nail dryer stopped working and I can't find the issue

Thread Starter

theboredunicorn

Joined Dec 12, 2020
20
Hello,
I have a Sunone UVLED nail lamp. For some reason, it stopped working yesterday. None of the lamps are glowing when turned on and because of that, I think that the fault is from the driver(uploaded pictures).
Here is how's it supposed to work: I plug in the connector to the dryer, then I hold button one(led 1), select for how many seconds I want it to work, put my hand inside the dryer(there is an IR receiver and emitter) and it starts working. I tried connecting the two ends of the IR's and start it again, but that didn't work as well. I have now idea what might be wrong with it and how to fix it. Can somebody help?

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Hymie

Joined Mar 30, 2018
924
It is nigh on impossible to fault find an electronic circuit based in visual inspection where there is no obvious damage (as in this case).

If you own a multimeter, you could trace out the circuit and make some rudimentary measurements that might pin-point a faulty component, but to be honest the effort probably would not be worth it given the cost of a replacement item.

Despite my introduction above, the electrolytic capacitor C1 (half way down on the left hand side) appears to be bulging slightly (indicating that it is faulty). If you have a 47µF 35V capacitor to hand – you could try replacing it.
 

Thread Starter

theboredunicorn

Joined Dec 12, 2020
20
I have a multimeter at hand. How can I check if the capacitors are ok?

The glass of the LED4 is broken, but when I turn on the lamp and press button 4 it lights up(LED4) but the UV LEDs do not work.
 

jpanhalt

Joined Jan 18, 2008
10,933
Can one assume LEDs 1 thru 4 are just indicator LEDs? What do the UV LEDs look like? Any obvious damage there? Did you damage LED4 or is that the way it looked when you opened the case? What color are the LEDs? Any clue what their part numbers are?

These 4 solder joints look poor:

1607861556087.png

That does not mean they don't work, and the appearance could also be just shadows. The upper right pair seem to be LED4. Assuming LED4 used to work, and it stopped working about the same time as the UV LEDs stopped working, my first assumption would be that those two events are connected.

So, what would cause both to fail at the same time? Too much current could make LED4 fail.

If you are competent at soldering, I would resolder what looks bad and replace LED4 . If it goes bad again, at least you can focus on why it has excessive current.
 

jpanhalt

Joined Jan 18, 2008
10,933
In my experience, a lot depends on when it broke. If it was broken for a long time before the UV lamps stopped working, I agree, the events may be independent. If the damage was concurrent, then they probably have a single cause.
 

Thread Starter

theboredunicorn

Joined Dec 12, 2020
20
Replying to post #6:
There is a small hole on LED4, but it doesn't go deep. I think that LEDs 1 to 4 are indeed indicators. I have attached a picture of one of the UVLED panels of the lamp. I also tested each one of the UVLEDs to see if they work by taking a wire and connecting the plus and minus and they all lit up. On the backside of the board, around the solder joints of led4, there was a bit of oxidation. I have a spare LED(I don't know if it's compatible) which I think I can solder onto the board.
When I measure the voltage on the solder joints(V+ and V- near LED4 like the pic from post#6) in the multimeter, it reads around 12.3V, which I think is ok, but then again I have no idea. Here is a link which shows that all of the LEDs work(the forum didn't let me upload the video,that's why I'm posting a link to my drive) https://drive.google.com/file/d/11uvd06V00OMgOXcuRkhPhfwGnLdYFHQ1/view?usp=sharing
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Last edited:

AlbertHall

Joined Jun 4, 2014
10,776
When the UV should be on, can you measure the voltages on the pins marked '1' and '2' withe black meter lead on the pin marked 'black'
Capture.JPG
 

jpanhalt

Joined Jan 18, 2008
10,933
Your newest picture gives a much better view. I have seen small bubbles in an LED's plastic case. They were that way originally and not caused by any failure. I would not worry if it is a bubble or even a hole if it was likely there originally, does not affect the active junction, and would leave it in place so long as it works for the time being. I was apparently misled by the work, "broken."
 

jpanhalt

Joined Jan 18, 2008
10,933
When I measure the voltage on the solder joints(V+ and V- near LED4 like the pic from post#6) in the multimeter, it reads around 12.3V, which I think is ok
I agree. That appears to be the input to the board from the wall wart power supply.

How many UV LED boards are there?

Under the same conditions, can you measure the input voltage at the UV LED board to which the wires from the control board go and at the output of the control board marked LED + and -. There are 8 wires, 4 red and 4 black. Only one pair (probably) is from the control board. Measure at that pair.

Do you get the same voltage at each of the inputs to the other boards. Let's say there are three or four UV boards total. I am trying to get a picture of how the boards are connected . One suspicion is that there is a failed connection/UV LED at one of the boards, and like Christmas tree lights wired in series,* only one bulb/connection needs to be bad to turn everything off.

*I don't know if they are still made like that.
 

Thread Starter

theboredunicorn

Joined Dec 12, 2020
20
Replying to post #14:
There are 5 panels with 3 UVLEDs and one big panel with 15 UVLEDs. The voltage on the control board at LED+ and LED- is 10.36V. I also get the same voltage on inputs on all of the other boards. Originally, I thought that the fault is at the IR sensors.I've removed the cables with which they're connected to the main board and then I used jumper wires to connect the two ends of the IR sensor pins to check if the problem comes from them, but that didn't work as well. Also, a mistake on my side. It turns out that the first button isn't for turning it on or off, but for changing the wats. By default it set on 24W and when the button is pressed, the wats become 48W(it might be in reverse though, I'm not sure). So now, when reading the voltage on the LED+ and LED- terminals i get a different reading. When the button is pressed - 10.36V on all panels and when it's not pressed - 12.28V on all panels. Here is a link with how the lamp is supposed to work

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jpanhalt

Joined Jan 18, 2008
10,933
OK, the boards appear to be in parallel, not series, which is good.

Now, if I understand, you are measuring between 10.4 V and 12.3 V (rounded) depending on whether the button is pressed. They look sort of luminescent to me in the pictures. If that is the case (i.e., they are lighted), then the problem seems to be in a sensor (as you suspect) or some as yet unidentified safety interlock device.

If that is correct, we are making headway. (One of the first things I do is remove safety interlocks from my tools. :) Some are a particular hassle when you are left handed. BTW, Bosch has made its interlocks ambidextrous.)
 

Thread Starter

theboredunicorn

Joined Dec 12, 2020
20
What exactly is a sefety interlock. From a quick google search I understand that it is "a device that prevents you from making an inappropriate maneuver, or adjusts the system to a safe state if you make an inappropriate maneuver". What I don't understand is how could I remove such a thing. Also tomorrow morning I'm going to the store to buy a new IR emitter and receiver and then test to see if it's going to work. Btw, thank for all the help you're giving me, i really appreciate it
 

jpanhalt

Joined Jan 18, 2008
10,933
Yes, that is the correct interpretation of the word. Basically, the IR detects when your hand is in the device and keeps it turned off or turns it off if no hand is present. If you have a self-cleaning oven, once you set it to clean, the oven door locks and stays locked until the cycle is over and the oven is below a certain temperature. Same idea.
 

jpanhalt

Joined Jan 18, 2008
10,933
Assuming the boards light when voltage is applied directly, and the mosfet referenced by AlbertHall is OK, I would be looking at the IR detector(s)/emitters.

How many can you identify? Any part number on them, particularly the receiver. I don't see any in the pictures. Perhaps on the back of the UV LED boards? They may look something like the pictures here and be dark red: https://www.vishay.com/docs/49588/ms6938-1912-ir_receivers.pdf

BTW, I have attached a datasheet for that mosfet or something similar.
 

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