Fixing/Upgrading a cheap LED light

[KingGlamis]

I have this cheap 3D LED light with 32 emitters (see pic below, the one on the left). It had decent light output but stopped working. It looks as though one of the LEDs may have shorted out on the backside of the circuit board. I see what looks like dirt or something between the + and - contacts of one LED, and when I look at that LED I can see a discolored spot inside of it that is clearly not normal. If I remember my electronics correctly it seems all 32 LEDs are arranged in parallel (all of them share a common + circuit and all share a common - circuit). And in a parallel circuit, if one LED blows, shouldn't the rest of them still work? Or are LEDs different than incan with respect to parallel and series circuits?

So my main question is how do I figure out what failed to cause the light to stop working? Is there an easy fix, for example running a jumper-wire across the contacts of the blown LED? And lastly, where would I look for possible upgrades to completely replace the 32 LED insert with something better, possible a single LED with a reflector (the reflector size would need to be 40-41mm outside diameter).

Thanks for any help. If you need pictures of the back side of the circuit board I will take them.

 

[DonShock]

If you are correct and all the LEDs are in parallel, then yes if one LED failed open then the others should work. However, if the failure somehow produced a short across the LED, then all the current would go through this low resistance path and none through the other LEDs. If that's what happened, it may have also damaged other parts of the circuit.

 

[lctorana]

OK, good question.

I have a 3-D Cell 32? LED Eiger flashlight, which I think is similar.

Assuming this is the same, the 32 LEDs are indeed in parallel, and direct driven from the three cells.

Since the torch doesn't work, there are only two possibilities:

1) An open circuit - most likely between the switch and the head.
2) A short circuit - I agree with Don that the most likely culprit is a shorted LED. In the case of a short circuit, something should be getting hot.

Take the head off the torch.

Test 1:
With either a voltmeter, or a 3.8V bulb, see that a positive is getting to the centre stud/spring contact ONLY when the switch is ON.
If this test succeeds, proceed to Test 2.

Test 2:
Connect a 4.5V 300mA power supply (a wallwart will do) via the 3.8V globe directly to the torch head with alligator clip leads.
Be very, very, VERY sure to get the polarity right. Positive to the centrre contact, negative to the case.
Both the bulb, and 31 or 32 LEDs should light up weakly.
If neither light up, there is an open circuit inside the head.
If the LEDs do not light, but the bulb lights up like Christmas, then there is the aforementioned short circuit is present.

If this test also suceeds, then the problem is the contact between the head and the body, and I usually jumper this with a 6" piece of insulated wire to a spade lug in this circumstance, discarding the normal spring-loaded contact rubbish.

Finally, I note this torch is quite unique for some reason in that it needs very fresh batteries to work properly - it is useless on rechargables, for instance. Never got to the bottom of that one.