UV nail curing lamp - dead?

[AndehX]

I have one of these UV nail glue curing lamp things, that I use for various none nail related stuff. I have only used it a handful of times, and it randomly died when I switched it on. Can anyone help me identify what exactly has failed? Checked the fuse in the plug, which is fine, but I have no idea what components to check inside.
I am fairly experienced with soldering and I have a good multimeter, so I am able to check for shorts/dead components. I just need to know where to begin.

Here are some pics.

 

[JimB]

Welcome to ETO.

Can I suggest that you post your pictures on this site.
As soon as I click on one of your pics to get a larger view, I get a security warning about the site where the pictures are held.

To post pictures here, click on the Upload a File button at the bottom right hand side of the post/reply dialogue box.

JimB

 

[AndehX]

Thanks for the info. Anyone have any ideas what could be wrong?

 

[alec_t]

The most likely component to have failed is one of the semiconductors, particularly Q1, Q2 or Q3. To test them properly they would need to be unsoldered and removed from the circuit (noting their orientation before removal).

 

[AndehX]

I can desolder them easy enough. How do I test them?

 

[alec_t]

What types of transistor are Q1,2,3?
What markings are on that 8-pin chip?

 

[AndehX]

The chip has no markings on it.



Q1 and Q2 are both 13003D

 

[alec_t]

Here's the 13003D pin-out :-

Q3 I think has a similar pin-out.
Using the diode test setting on your meter you can determine if the base-emitter and base-collector junctions of each transistor look like workable diodes. The Ohms range can be used to see if there is extremely high resistance between collector and emitter when the base is shorted to the emitter. If these tests are passed there's a good chance the transistors are ok, but high voltage breakdown is a possibility.

 

[AndehX]

ok, I "think" im following what you're saying. I'll desolder them in a bit and see if I can work out how to test them

 

[Les Jones]

While trying to find a schematic of these devices (Which I failed to do.) I found this youtube that gives some useful information. It looks like the 8 pin chip is a timer so that can be ignored as in the continuous on mode the lamp driver is driven directly. My initial approach would be check the voltage across the main reservoir capacitor with it switched on in the continuous mode. As the price of the unit in the youtuble was given in UK pounds then the mains voltage would be 240 volts so I would expect about 340 volts DC across the capacitor. If this is OK then I would trace out the schematic before removing parts.

Les.

 

[AndehX]

ok so i tested the voltage on that big 400v cap, its got 320v DC going across it