Repair of LED plant grow light after massacre of LED module - Page 1
Forum section: electronics / repair

author: nightfire
author_rank: Frequent Contributor
timestamp: October 23, 2022, 12:58:55 am
content: Situation: As a becoming next Michelin-level star of home cooking (ok, at least I have not poisoned someone yet with my kitchen skills...) I decided to invest some time in growing some own herbs in my apartment, as I do not have ressources like a balcony etc.(I do like to use fresh parsley a lot in my dishes, and autumn season calls for some hearty soups)As some grow light became available on ebay, I went for it- and because "one bank ceased working some time ago", I got it as a defective item for a good price.After all, with those simple designs, what could have gone bad? Usually one of the LEDs that are working in series or the LED driver itself have some issues, so repair would have been no big deal.https://www.ebay.de/itm/Meizhi-R50-60-LED-Grow-Light-Pflanzenlampe-Zimmerpflanzen-Veg-Flower-/354314216294?mkpid=0&emsid=e11050.m43.l1123&mkcid=26&ch=osgood&euid=1c37d88037ed4494ae10f424fe453d43&bu=43203972229&osub=-1%7E1&crd=20221018151813&segname=11050&nma=true&si=akV2sregvvVLwo%252FGHm9jcAKxve8%253D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557After opening it, I was greeted by the sight of 16 missing LEDs out of 60- and only the blue and violet LEDs have been harvested by force. (ALL of the blues, every other color present)Attached pics show that someone ripped them off the aluminum mounting panel, sometimes damaging the copper soldering points.I am actually not sure if I should accept the challenge and rebuild the panel, learning lots about LEDs and plant grow lights including the spectrum used, or, if the (financial) effort is in no relation to the former going price of about 100 € for the unit, better invest the money elsewhere...I would appreciate some help in determining the LED types/packaging type, as I seem to struggle to get the right packaging type.The still existing LEDs have a diameter of 8mm at the broadest plastic packaging point, the middle of the soldering pads has a distance of about 12mm, and the bare metal mounting pad where there is some leftovers of the thermal paste is about 5mm- those LEDs have a power consumption of about 5W.Also I would appreciate some hints how to fix the broken soldering pads- other than clearing some of the isolation of the copper traces and soldering some wire to them...Aaand: If someone has some links to good articles dealing with growing herbs like parsley and basil and their lighting requirements, I would be very happy ;-)Edit: LED Power should be less than 5W, only input wattage would be that high, so rather we are talking about 2-3 Watts per LED here.

author: thm_w
author_rank: Super Contributor
timestamp: October 25, 2022, 12:59:51 am
content: These are probably standard "3W style" LEDs:https://www.aliexpress.com/item/2004334007.htmlYou can see the metal thermal pad on the bottom. which would want to use thermal paste to connect to the board.To scrape off the soldermask you can use an xacto type knife blade or a dremel with a small abrasive wheel. Find tutorials on youtube.The torn pad can be jumpered but may no longer be strong enough to support the LED. So might need to surround the LED with silicone.

author: james_s
author_rank: Super Contributor
timestamp: October 25, 2022, 01:02:19 am
content: I worked on one of these for somebody a while back, I found quite a few defective LEDs and ended up scrapping it. They're cheaply made and not really worth the effort to repair IMO.

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: October 25, 2022, 01:15:49 am
content: Grow light for my "parsley".

author: nightfire
author_rank: Frequent Contributor
timestamp: October 25, 2022, 07:11:31 pm
content: Yes, it is no high-tech buried inside. But, on the other hand, the rest of the case and stuff is made quite nicely, way better than most of the el cheapo chinese junk I have seen.I just ordered a pack of cheap blue LEDs on ebay, and will try to get the stuff running- let alone for sake of learning something when I work on that.I mean, after all, including the new LEDs, I will have paid less than 40 € for everything, and thats not exactly cheap, but very reasonable for the stuff I intend to use it.Also herbs growing is new to me, so there will be a bit of stuff to go through.

author: 2N2222A
author_rank: Regular Contributor
timestamp: October 25, 2022, 11:31:36 pm
content: QuoteI think they power the LEDs to the point where the life is significantly reduced. If it's 3W per LED and it's from China then bring it down to 2W so it will last!

author: Prime
author_rank: Regular Contributor
timestamp: October 28, 2022, 10:49:23 pm
content: If memory serves me correctly those are luxeon rebel style LEDs.As for repairs, the pcb is likely to be aluminium backed so you'll need to warm the surrounding area to resolder as it will suck the heat out. You might be better off with electrically conductive epoxy.Lastly, the centre of the led is supposed to be attached to the board to sink the heat away. Failure to achieve this will result in very short life at 2W.

author: nightfire
author_rank: Frequent Contributor
timestamp: October 28, 2022, 11:12:47 pm
content: Yes, I am afraid of that.I also thought of using electrically conductive glue instead of thernal paste and conventialan soldering.

author: james_s
author_rank: Super Contributor
timestamp: October 28, 2022, 11:57:35 pm
content: I've had success with that style of LED by using a dab of heatsink paste under the body of the LED and then soldering the leads. Aluminum boards can be a challenge but it works if you crank the iron up high. If that isn't enough, heat the whole board to around 100C on a hotplate or with a heat gun from underneath.