Help with Diagnosing RapidLed DIY diode problems

[Curt2199]

I could use some help troubleshooting some LED problems.

I have 4 x 36 led Rapidled DIY using 3 x Meanwell ELN-60-48D drivers per fixture. There are 36 solderless Rapidleds with a mixture of Blue and White CREE and unknown brand Rapidled violets. I purchased them used but in like new condition and they had no lenses. I've been running them like that for a while over my 48" deep tank but would like to start trying more SPS so I ordered 144 x 40 degree lenses from Rapidled.

After applying the lenses with arctic alumina and 5 min epoxy (ran out of alumna) I ran into some issues. First, 70% of the led diodes had some solder preventing the lenses from sitting perfectly flat so I tried to get them as flat as I could when applying the adhesive. Once I had them all done, I'm having issues with the violets and am wondering if I killed several of them. Of the 4 fixtures, 2 have one violet not lighting at all (rest of leds in circuit light fine, forward voltages on the violets are low at 1.8V and 2.2V). 1 fixture is perfect and the very last fixture has most of the violets not lighting properly. I'm going to focus on this fixture for now and see if I can find out what the problem is.

First, on the circuit with the majority of violets not lighting properly (either dim or not at all), I removed all of the lenses and glue and cleaned with alcohol. I tested all of the diode contacts on the whole fixture for grounding against the heatsink and all showed open. I tested all leds with the diode mode on my multimeter and none of the violets light (even the one that seems to be lighting properly) but all blues and whites do. I'm not sure if it's normal for violet leds to not light with the diode test? Also the white plastic terminals for the wires are showing yellowing (heat) on all of the violets.

Here are the results of testing the circuit with my Harbor Freight Multimeter in series in order for forward voltage (FV) (powered) and diode test (DT) (unpowered).

1. Violet (Dim) - DT (61) - FV (2.91)
2. Blue (Lit) - DT (Open) - FV (3.04)
3. Blue (Lit) - DT (Open) - FV (3.05)
4. Violet (Lit) - DT (1473) - FV (3.55)
5. Blue (Lit) - DT (Open) - FV (3.02)
6. Violet (very dim) - DT (18) - FV (2.51)
7. Violet (Unlit) - DT (2) - FV (0.17)
8. Blue (Lit) - DT (Open) - FV (3.05)
9. Violet (Dim) - DT(27) - FV (2.77)
10. Violet () - DT(31) - FV (2.64)
11. Blue (Lit) - DT (Open) - FV (3.01)
12. Blue (Lit) - DT (Open) - FV (3.04)

Attached a pic of the setup as is and far right fixture is the one with most of the violets not lighting.

[theatrus]

Violet LEDs tend to have a somewhat higher Vf that royal blue (3.5+), so its quite likely your multimeter can't light them in diode test mode. 3AA batteries and a ~1k ohm resistor in series should allow you to test these safely.

Did the violet LEDs work at all post lens installation? Heat death would be not be instantaneous as long as they were attached to a heat sink. Its possible you cracked the solder joint on the diode/PCB interface during installation or adhesive curing.

[AZRippster]

Curt,

Try posting this to the Rapid LED vendor forum. Mike or one of the guys will likely chime in pretty quick to give you some advice/help.

[oreo57]

Violets burn out easily..and do not like lenses...and they will be dim since the eye is not a sensitive to that color..being used they could be at EOL...

[Curt2199]

I think I probably damaged them pushing lenses down on them: