Without one of them shorted, do any of them light?

Apparently not. I was wondering about the power supply. But the TS has also used another supply. Still a mystery. Maybe only the top LED is in backwards (joke...device worked at one time).

 

Apparently not. I was wondering about the power supply. But the TS has also used another supply. Still a mystery. Maybe only the top LED is in backwards (joke...device worked at one time).

That would seem to suggest not enough voltage.
Does this plug direct to the wall socket or does it have a 'wall wart' box?

 

From what I saw in the earlier pictures (post #10) the supply for the nail drier is a wallwart (12V at 1A). However, the supply used in the current testing looks like a typical standalone supply.

 

Your tests with shorting one of the LEDs indicates that the board is supplying sufficient voltage to light two but not 3 LEDs.

Can you measure the voltage when the two are lit and when the three are connected bit not lit.

Bob

 

the supply for the nail drier is a wallwart (12V at 1A)

Yet they claim it is 48W

 

Without one of them shorted, do any of them light?

No, if I don't short an LED, none of them light, even though it's plugged in.

Here's what I see in the video:

View attachment 225173
That is, when you short across one LED in a string, the other two in the same string light. Now, if you short across the middle LED, do the other two light?

Can you attach your voltmeter across the supply leads (LED+ and LED-). It should read about 12V. What does it read? When you then short across an LED and the other LEDs light, what does it then read?

EDIT: There is presumably a 39Ω resistor somewhere in that string. What happens if you BRIEFLY short across that resistor? If you have a small resistor (10 to 50 Ω) you should add that in series with your shorting lead.

If I short the middle light, the one on the right and the one the left light. When I attach a voltmeter it reads around 12.3V. When I short across an LED it also reads around 12.3V.

 

u run a test by con

Earlier I desoldered one of the panels with 3LEDs and connected it to another power supply. I can change the voltage on that one, so I tried using less voltage, but that didn't work. Next, I tried using more(max 15V) and that didn't work as well.

 

No, if I don't short an LED, none of them light, even though it's plugged in.



If I short the middle light, the one on the right and the one the left light. When I attach a voltmeter it reads around 12.3V. When I short across an LED it also reads around 12.3V.

Thanks that information matches my latest schematic. And, If the supply is current limited, I don't see the voltage drop I expected to see. Raising the total to 15 V should have lighted all three.

UV LEDs vary in forward voltage drop (I've seen figures from 3.5V to 6.5V); however, your 12V supply did at one time lighted them all. I would be hesitant to go above the 15V you have tried. Maybe a very brief 18V, preferably with a 10Ω resistor in series could be tired. But you don't have that, and I believe it may be something else. Not sure what.

 

There is a small inductor to the right of the 8 pin chip. I am wondering if this could be part of a step up converter. What is the part number on the 8 pin chip ? (I can't read it from the picture.) Looking at the datasheet on the UV LEDs (From the link in post # 42) it is not clear about the voltage rating of the LEDs. In one place is says 6-7V in another it says 3V/6V. If they were 6 volt then that would explain why shorting one LED in a chain of 3 made the other 2 light. One other possibility is that you may have used the wrong power supply. (If you have a few similar looking power supplies.).

Les.

 

New theory, let me throw it at the wall and see if it sticks.



There is an inductor on that board. Maybe it is a boost supply. The mosfet died "on" and there is no boost. Maybe the supply for each string need to be 18V or even 24V?

@LesJones
You beat me to it. Just got back from the P.O. and the thought occurred to me during that drive.

 

I advised in post #2 that the effort required to repair the unit would not make it worthwhile – which has proved to be the case.

 

I advised in post #2 that the effort required to repair the unit would not make it worthwhile – which has proved to be the case.

Who cares about a few $. I observed the same much later.

Unless, of course, you want nice nails for this week's really big football games. I know I do as Ohio State dominates Northwestern. Justin Fields is no match for anything NW has.

 

Update: there wasn't anything broken within the lamp. Turns out, it was the wrong power supply

and there just wasn't enough voltage as the latest post suggested. Sorry for all the time I took from you guys, but on the bright side, I learned some basic electronics

https://drive.google.com/file/d/1rYJYpyWkkHNI6rN5vRu7t96brMoetBdk/view?usp=sharing

 

Thanks for letting us know that it is now working.

Les.