72 volt led chip

KevinW

Member
I have an outdoor security light that has a few open led chips that I want to replace but the voltage is 72vdc and I believe .5 watt chip.
Can't seem to find a chip like that on line so I wanted to ask, are some of these chips actually 72vdc ?
 
A single white LED is almost always around 3 V, but it is very common to have many in series in one package.

Getting hold of odd packages can be difficult.

72 V and 0.5 W is only 7 mA, which is very small. Most LEDs for illumination run at higher currents. How did you measure the voltage? LED driver circuits usually run at approximately constant current, so if the LED goes open circuit the voltage across the LED will increase. If you measure the voltage with failed LEDs, you won't get the correct reading.
 
The amperage I looked at was around 300mA.
There were leds missing but I can test a lamp that still has all working leds.
There are 8 chips on 6 lamps all together , 48 chips in total.
You can see the metal contacts in the center, that's where I measured the 72vdc.
The plate on the back reads C2440-kw-27W
ac120v , 60Hz , 0.59A ,27W , cct:5000k.
 

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I can't see the detail, but the LEDs are almost certainly in series. I would guess that the 8 chips are in series, totalling 72 V, so that the is 9 V on each chip. You could confirm that on a working one by measuring the voltage across one LED chip. I have seen LED chips with three separate LEDs, each wired to two terminals, so the assembly has 6 terminals. It could be that you have something like that with all three wired in series.

If the plate on the back is correct, that is 27 W in total, or 4.5 W per lamp, so that is 62.5 mA at 72 V. So you are looking for LED chips that are 9 V (3 LEDs in series) and rated at 62.5 mA (or 560 mW) or more.
It is quite likely that the chips are rated to a higher current than they are being run at, so if you find some higher-rated LEDs chips that are still 9 V, they will be fine.
 
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