need help from DIYers LED DIODE EXPERTS

[ZoWhat]

I have a fixture that I retro'ed the 3watt diodes pictured below. Simple process of unsoldering the Mfgr diode and resolderiing my choice of diode in whatever nm color

PROBLEM: Fixture doesn't seem to have good enough ventilation to keep my 420nm diodes operating temp cool.

I know 420nm run SUPER hot.

After about 60-90 days the tiny CLEAR LENS that caps the diode onto thediode, get Black and charred from overheating

BUT! I'm noticing if I pry off the CLEAR LENSE the diode still has a JELLY-like substance surrounding the diode chip. That's represented as the RED BLOB I put in the diagram below

QUESTIONs:
If I removed the charred clear lens and left the diode with the Jelly bubble and just silicone sealed the LENS CAP back on (picturedbelow)...what am I to expect?

Diode goes on being a diode for a long time?
Diode overheats and burns out?
The Jelly gets contaminated and destroys the diode chip?

Ideas?

 

[Daniel@R2R]

Bump for input from #reefsquad or other #DIYwizards

 

[bblumberg]

Is the diode making good contact with the heat sink? Adequate amount of thermal compound?

 

[redfishbluefish]

My experience with fried LED's is that after the primary lens has charred and melted, the LED continues to emit light. Either leave it be (removing the charred lens) or if you have new primary lenses, super glue (cyanoacrylate glue) them back on.

Don't know why yours are burning out so fast. What thermal grease are you using? Yes, they don't last, but I'm going to say I get 2 - 3 years out of the UV beads I use. I always have a supply on hand and order directly out of China.......HERE.

 

[BrandonS]

I would say make sure to have thermal compound. Also when you solder make sure the led is flat against the heat sink. Sometimes the solder can hold the led up a bit depending on technique. If that's all squared away then yes you can run without the jelly like stuff and lens. Just exposes the diode to salt and air. Have you only used leds from same batch or have you tried different batched/ suppliers? LEDs are made in large batches so a bad batch can constitute of tens of thousands of LEDs. We had a bad batch at one of my old works that caused the red color on an smd to only fail once it heated up. On a very large display for times square, millions of diodes all from same batch. Delayed us 3 months.

 

[ZoWhat]

Is the diode making good contact with the heat sink? Adequate amount of thermal compound?

Yes. Using the ArticSilver stuff I've used with CPU processors

 

[oreo54]

Just bad material or glues for the outer lens,
Primary (does "jelly" seem like silicone?) should be good enough though widens the beam angle.

https://www.led-professional.com/re...on-through-volatile-organic-compounds-by-cree

The photograph on the left shows the normal appearance of an LED. On the right, the same type XLamp chip has a pronounced brown discoloration due to exposure to VOCs while in operation with high photonic power output and at nominal environmental temperatures. This discoloration of the encapsulants is on the top of the LED chip, localized to the area just above the chip surface, closest to the source of heat and high photon energy. The VOCs occupying a free space within the lens or encapsulant typically do not cause permanent damage to the silicone material or the LED chip. In many instances, removing a secondary optic or otherwise venting the LED’s environment will allow it to clear and recover in just a few hours of operation. However, the discolored VOC in the silicone polymer will not clear if the LED’s operating environment remains saturated with the VOC.

LED and Lens Degradation Through Volatile Organic Compounds

In general, LEDs are very resistant light sources. Nevertheless, glues, conformal coatings, o-rings, gaskets, and potting compounds, all materials that are frequently used in the construction of LED based luminaires or lamps and often contain volatile organic compounds (VOCs) may have a negative...

www.led-professional.com

 

[ZoWhat]

My experience with fried LED's is that after the primary lens has charred and melted, the LED continues to emit light. Either leave it be (removing the charred lens) or if you have new primary lenses, super glue (cyanoacrylate glue) them back on.

Don't know why yours are burning out so fast. What thermal grease are you using? Yes, they don't last, but I'm going to say I get 2 - 3 years out of the UV beads I use. I always have a supply on hand and order directly out of China.......HERE.

UPDATE: the fixtures I'm retroing are LEDGLE fixtures that are discontinued. I was reading today LEDGLE quickly pulled my fixtures off the market a few years ago after reports of the fixture running SUPER HOT. Might even had a lawsuit with a fire hazard but one write up fell just short of saying it was a fire hazard in the review.

The backing of the curcuitboard is straight up FLAT aluminum with NO ROOM for heat fins. Nothing.

Just 3 inline std 80mm computer fans blowing straight down and out the sides

BEGS TO QUESTION.... is there any heat dissipating paste that can be applied to BACK of the curcuitboard to help with heat?

There is no physical room for anything like radiating fins.

Thought about hi RPM 80mm fans but it would prob make the tank sound like a vaccum

Any thoughts?

 

[oreo54]

W/ out a pic (can't really find it atm) there is no way to give any help..
One thing though, there are fairly easy ways of dropping the current a bit..
you don't lose as much output as you would suspect since cooler diodes run more efficient..

 

[ZoWhat]

One thing though, there are fairly easy ways of dropping the current a bit..

The fixtures do have dimmable dials.

I run the 420nm all on 1 of 2 channels at 50% power 50% dial up... uet they still get charred.

This fixture has a poor heat displacement design or smthg...

You talking using powersupplies that are a little less wattage.

I would need this spelled out for me

 

[oreo54]

The fixtures do have dimmable dials.

I run the 420nm all on 1 of 2 channels at 50% power 50% dial up... uet they still get charred.

This fixture has a poor heat displacement design or smthg...

You talking using powersupplies that are a little less wattage.

I would need this spelled out for me

Need to know how it's constructed..
If constant voltage one can decrease the voltage a little. If constant current need to drop the current (usually replace the drivers).

If you are already dimming you effective current is low so really not an option.
You notice that the diodes themselves aren't burnt.

Just remove the burnt lens like you did and run em.......... Really just seems like a really bad batch of diodes.

Sub-blue diodes aren't as efficient anyways meaning more heat as they are.
Are other diodes burnt? Probably not but sometimes blues go.

If there is a circuit board attached to a block of aluminum, yes you can put thermal compound to help fill the "gaps".
Yes bigger fans may cool it more..still don't think its the real or best solution.
Cheap chips high current driver is the likely issue over heating.. Yea if you could run them in a refrigerator..probably less issues..well longer time between failure of the plastic.

400mA-500mA / 3V-3.2V

Still need more info on the light itself.. Search isn't coming up w/ anything concrete..
got a model # at least... "may" help.

 

[ZoWhat]

Sub-blue diodes aren't as efficient anyways meaning more heat as they are.
Are other diodes burnt? Probably not but sometimes blues go.

@oreo5457

So plz read thoroughly below......

Big Questions first:

* Am I just working with the wrong fixture? Not meant to drive 420NM all in one linear channel.

* Am I working with wrong 420nm diode? It's too cheap to expect any results past 6mos to a year at <50% power

* if I were to change fixture... what's recommended as a good retro fixture? MY GOAL IS I WANT TWO CHANNELS 420 & 460 to grow my zoas/palys dominated tank

* if I were to change diodes to a different 420nm diode, what's recommended?

-----------------------

Correct! The 420nm diodes char the diode lens while my 460nm diodes I can run at 100% without charring.

So in total i have 4 of these LEDGLE fixtures

I know...I know.... cheap black boxes.

420nm all on Channel 1 = if I push even to 50% within 90 days they start to char the diode lens

460nm on Channel 2 = these are champs that I can run at 100% and maybe have seem 1 or 2 diodes in a year get charred

Heres the "official" spec. BUT WHAT DOESNT MAKE SENSE IS THAT 5W IS LISTED BUT ONLY 3W DIODES WORK. IVE TRIED 5Wters ABD THEY WONT LIGHT UP.

Specifications:
LED Power: 60x5W
Actual Power:120W±5%
Input Voltage:AC85-265V


Here is what I'm buying thru Ebay thru a Chinese distributor:

 

[Silent]

Isn't that burnt cover just there to narrow/focus the beam? You might lose par but light will be more spread out.

 

[Cory]

Could you buy glass diodes instead of plastic? Not glass diodes but covers or whatever they are called.

 

[Silent]

Could you buy glass diodes instead of plastic? Not glass diodes but covers or whatever they are called.

I think they are called "optics".

 

[Cory]

I think they are called "optics".

Lol yeah get glass optics.

 

[BrandonS]

Not all black boxs are bad. Have some viparspecras I love. Its possible they are overdriving the blues. Maybe bad driver. Are you using bridgelux LEDs? Once you get close to true UV. Sub 400nm it just fries plastic usually. That's what UV does. It's why plastic gets brittle and browns out in the sun.

 

[bblumberg]

Yes. Using the ArticSilver stuff I've used with CPU processors

Great, just don't use too much. A very thin film is all you need.

 

[ZoWhat]

Great, just don't use too much. A very thin film is all you need.

Actually was watching a couple IT testing nerds that did a Mythbusters on "too much" vs "too little" thermpaste.

Perfectly thin coat vs a heavy. ... yielded the same exact bench test on TEMP. Only SIDENOTE was the paste can become conductive causing electrical-shorts