Cobs Suck !!

I ran cobshop cobs prior to running boards. My first grow with boards murdered the cobs and they got sold for more boards.

@RainDan helped me 1,000,000,000%. Rare service. Glad I bought 2 of his lights now for sure !!

bk78 said:

I ran cobshop cobs prior to running boards. My first grow with boards murdered the cobs and they got sold for more boards.

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I love my 240w qb as well. Excellent.

nunyabidness420 said:

Hi @RainDan
Out of curiosity, what should the heat sink temperature be once the light has warmed up to its maximum operating temperature?

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when we test them they get to 125-135F in the absence of a fan. Adding a small clip on fan generally drops the temps by 15-20F.

RainDan said:

when we test them they get to 125-135F in the absence of a fan. Adding a small clip on fan generally drops the temps by 15-20F.

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125-135f is already pretty cool.

I have four vero 29 fixtures from timber.. been using them for 4 years now I guess... never had an issue or malfunction.. love the results.. nothing but good for me..

Southside112 said:

The 4 original cobs were installed by Timber and were installed right. Timber came out like 2 years ago and told all owners to take the reflectors off because others were having issues with them melting. I suspect it is a vero 29 issue. Too much heat generated @ 100w each. Like I said most cobs run @ 50w.

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I've had 16 Cree cxb3590's for six years. I bought them from timber. The only issue I ever had was a driver failure right after I bought them. @RainDan was all over it, and had me a new driver out next day air immediately. Although my lights are outdated by today's fixtures, they're still damn good lights and paid for themselves many times over.

I have cree cobs going on 5 perhaps 6 years old. Completely issue free.
I do run them at 55 watts each though.

all my cree cxb3590 lights still work and never have any failed. i do run them at 50 watts a cob though. i have 8 of them with 4 cobs per fixture. i built all of them myself.

Timber is quality. Some of my issues were my own doing. Full disclosure.

I use 4 50w timber cree without reflector on the corners of a 150w qb. Started with a mh blurple. 3x3x6 tent...it works for me but I'm an amateur. Timber been running since 2016 almost non stop. .guy at timber was very helpful btw

I bought my 6 cree cobs as a kit from Timber in 2016.. No problems in 5 years..
Dan's great to work with too..

Cobs are in an awkward position between the high light point source of hps, and the spread of QB boards. There is a very fine line to play with in terms of the best intensity/spread range for cobs. The canopy has to be fully filled in at the net with leaves, yet you want colas sticking out above the net at about 6-8 inches. All those colas are in optimal range, yet any light getting past them still hits the net canopy leaves and secondary bud sites at a good intensity.

The intensity of cobs are more focal, they do give them more penetration in a single straight line down over qb, but past 12 inches or so it quickly drops off because the over lap intensity also drops off due to the focal light. I've tested this with a light meter. You can not lower cobs too much or they will give you worse heat stress than hps, you can not raise them too high because they don't give off good enough intensity by the time you reach a even spread sweat spot. You have to get the spacing between cobs right, the height between the canopy right, and the shape of the canopy right, with fine margins.

QB are easier because the over all spread translates to the upper foot of canopy very well. You can also get them a little closer due to the spread, without burning/light stressing tops, this increases over lap intensity and in tern adds a little to the overall depth. They might not penetrate as far as cobs, but they spread the light out a lot better in the range they do penetrate too. For that reason alone they are better, although cobs are still very good if you do it right.

I had 4 generic 100w COBS burn out on me this year. I could never keep them cool enough. I am sitting here waiting for my QB kits to turn up, 2 x 150w with Samsung LM301hs and Meanwell drivers. I am like a kid waiting for Christmas.

I wouldn't say COBS suck. I have had some really decent grows out of the 4 that failed. They lasted a good 18 months. I have 4 lower wattage COBS I am going to use for the corners. I will replace them with another pair of the QBs before they fail.

My first three years was with 3-100w 32vdc chips. Still have them but they need replaced. Big heatsink and a fan on each with a diffuser dome. 32Vdc was s PITA.

Next were some of these, 50 watt and full spectrum. They do not get too hot to touch., had them three years now. Not strong enough on their own though. Good for the small stuff or side lighting.



These get too hot and need a fan.

Southside112 said:

Just want to share my experiences with cob led's so far. So I have been running cobs in addition to other white led's for 4 years now.
Vero 29's to be exact. 4 years ago I bought a Timber 4vs which is a 400w 4 vero29 unit. I have replaced all 4 cobs already due to burning out and tonight 2 more burned out on me. 2 of the original cobs were replaced with graumaus pucks. So I have 2 pucks and 2 vero 29's on the unit. My current grow is in flower and stretching at the moment. I raised up my light like 6" tonight and got my par meter out. Turned up the power on the unit from like 60% power to like 80% power. Instantly smelled a burned electronic smell followed by flickering lights. Boom both cobs burned out and went dark. Took out the unit to much inconvenience as I have 4 flowering plants in my grow area. They were all burned up melted and black around the cobs.

Bottom line imo is cobs generate way too much heat in too small an area. 100w of cobs concentrated to an area the size of a key lime. Vero 29 cobs are the only ones to my knowledge that can run constant 100w most others run @ 50w. So this might just be a vero issue. But numbers don't lie. 6 burned out vero 29 cobs in 4 years.
I placed an order for 2 more graumaus pucks from rapid led tonight. So my unit will be a 400w 4 graumaus puck moving forward.

Never had an issue with the pucks or a 240w qb I have only cobs. So to anyone who reads this do yourself a favor and go the qb, strip or puck route. Save yourself all the hassles ive had to deal with. Thanks.

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Sounds like your running them too hard. I had some and they were great. I did replace them all with qb96 elites which fit on the same heat sinks tho.... an amazing move.

Three Berries said:

My first three years was with 3-100w 32vdc chips. Still have them but they need replaced. Big heatsink and a fan on each with a diffuser dome. 32Vdc was s PITA.

Next were some of these, 50 watt and full spectrum. They do not get too hot to touch., had them three years now. Not strong enough on their own though. Good for the small stuff or side lighting.

These get too hot and need a fan.

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They are exactly the same as the ones I am going to use for corner lighting. 100w a piece.

Stealthstyle said:

never in three or four years have i had those troubles with cobs

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Me neither, mine have been running for years. Pretty much around the clock. He needs to start from scratch and recalculate. I have a dozen cobs that I run passively at 80 watts. Not a single issue

speedwell68 said:

They are exactly the same as the ones I am going to use for corner lighting. 100w a piece.

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Those black ones need a fan on them. I've got one single and two doubles. Three have burnt out.

The white ones have a huge copper heat sink the chip is mounted on inside.

Timber all the way going on 4 ish years I think... ans now seeing this I am glad i sprung for the crees when I did!