Help with intermittent fault on a CXB3590 panel

Hoping one off you more learned characters can help me with an aggravating fault I have with a DIY CXB3590 panel. I’ve had the last 2 cobs in series not light up twice now. Before I explain further I should probably give the spec.

Spec:
This panel is about a year & a half old & to date has operated as expected with no issues till now. It is 4 x CXB3590 Cd bin 3500k attached to a HLG-240-C1750B driver.

The cobs have never been driven over 40w each so it has not been pushed.

The heat-sink hits the minimum spec for passive cooling but has 5 x 120mm fans attached to it (I like to over engineer) so over heating should not be an issue.

The cob in the middle is on a separate driver so could not be causing the issue (Cannibalized from an old blurple I had left over).

Fault:
Last Friday when my lights were due to switch on, only the first 2 cobs in the series lit up. I unplugged them at the wall & had a fiddle with the wiring & just made sure everything was still solidly where it should be. Plugged back in & still no joy. The plug-in wattage meter also only showed the power draw at half of what I would expect. When turning the potentiometer up & down the wattage meter only displayed the wattage range you would expect for only 2 x cobs.

I unplugged it & went to get some tools. When I came back I thought I’ll try it one more time & low & behold all 4 fired up.

Today the same thing has happened but this time I could not get the cobs to light back up. Now I have an inkling that the power supply is at fault here but that is a best guess.

I have another HLG driver on a Samsung strip build I use for veg that also has the correct power output to power 4 x cobs so I thought, process of elimination. I’ll cut that power supply out & switch them over & see what happens.

Tested the existing power supply one more time before cutting the cable on the other power supply. Still no ball so I cut the cable on the HLG driver from my Samsung build. I guess in future I should invest in some sort of quick connect fittings of some sort.

Anyway, I was about to cut the existing HLG-240-C1750B out to put in the new driver & I thought I know what’s going to happen here, Murphy’s law will apply. I plugged in the power cable for the existing driver one more time just in case & all 4 cobs lit up perfectly. The wattage draw shown on the wattage meter is what I would expect for all 4 cobs running as normal.

So, I have no doubt this will happen again at some point but being intermittent this may be hard to diagnose.

It’s either the driver or the last 2 cobs in the series are starting to fail. I’m leaning towards the driver being the issue but like I said that is a best guess. Before I start buying replacement parts I would like to be a little surer of what is going on here.

Any help would be appreciated.

First I would do is check the output voltage from the driver When all 4 are working and again when the 2 is not working. Then I would check the last working string of the cob to see if it's passing enough forward voltage. Check your contacts and plugs on your holders.

Thanks for the advice @jarvild. That's a very good idea. I should have thought of that myself! I'll test that out when its lights on again

Check every connection in the chain with a multimeter while moving any moveable parts attached to the point.

Thanks @ANC. I did check the connections at the cob end today but neglected to check the driver end before the 2 in question came back on. Will break out the multi-meter go full exploratory on it at next lights on.

Bad connections start fires... also undo the panel at he wall and do a good inspection of the wall receptacle's insides (with the main breaker to the house or at least that receptacle, turned off).

I don't think it’s a loose connection. Nothing has been moved or yanked on. The only movement has been the panel being raised & lowered which does not put much strain on any of the connections. Plus, I tend to over engineer everything which in theory sounds great, until you try to take it apart.
All that said & done, better safe than sorry. You raise a valid point. I'm going to go to town on it so to speak. At next lights on regardless of the fault showing or not I'm going to go over every single connection & power point. That will involve some re-wiring but will rule out a loose connection being an issue.
After that all I can do is wait for it to happen again & break out the multi-meter.
I’ll update the thread when I know more just in case anyone else has similar issues at any point.

do these drivers contain a fuse? do you have a variable DC supply you could use to check your chips?

The ac input to the driver should be fused somehow, safety safety.

Sounds like wiring, or possibly driver faulty. You were on the right track with swapping the driver, see if problem follows light or driver, proceed. Wiring issue could follow with the light, but you'd find that out later

kushedy said:

It is 4 x CXB3590 Cd bin 3500k attached to a HLG-240-C1750B driver.

Last Friday when my lights were due to switch on, only the first 2 cobs in the series lit up.

It’s either the driver or the last 2 cobs in the series are starting to fail. I’m leaning towards the driver being the issue but like I said that is a best guess.

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What are the odds of two cobs being intermittent in perfect synchronization? With cobs in series, they all run at the same current, they should all be on or off.
I suspect a short across the two cobs that are intermittent.

Maybe the 2 that are turning off are higher voltage for some reason or they are getting hotter on that side

Do you have a potentiometer connected to your driver? If so, remove it and try your light without any pot.

@psychedelicdaddi yes, the plug I attached to the driver has a 13 amp fuse in it. I only have one other Meanwell HLG driver to use to test the cobs. I haven't yet as they all started working again.

@CannaBruh it’s just a waiting game now till they next play up & then I can trouble shoot some more

@1212ham what you are suggesting does make sense but based on how I built it I think it’s un-likely (but not impossible). I couldn't find any solid core wire in the UK when I built this so used threaded. As such I had to tin the ends that were inserted into the ideal holders. I also soldered all wire joins & wrapped in quite a lot of amalgamation tape so theoretically everything should be sound. It has all worked perfectly for a year & a half which also is edging me in the direction of thinking it’s a faulty driver.
4 x 36v cobs does max load the driver. Maybe it has been a bit to much & the driver is slowly breaking down.

@Ryante55 could be. That side of the heatsink does not appear to be any warmer than the other. I appreciate that is just a touch test so not very precise. I would be surprised if overheating is the issue. The heat-sink is big enough for passive plus it has 5 x 120mm fans strapped to it.

@klx Yes, I do but not really an option. Full power would be 1.75amps & I don't have the headroom to run that much light. I'm half way through the 2nd week of flower. I can't really afford to fry my plants. That would have to be the last resort in trouble shooting.


I can now get solid core cable fairly easily so I am planning on doing a complete rewire of the panel just for peace of mind. All cobs came on again at lights on so bar a bit of connection checking I can’t really fault find anymore at this point. Thanks for all the responses. Much appreciated. I’ll update the thread as soon as I know more.

kushedy said:

@klx Yes, I do but not really an option. Full power would be 1.75amps & I don't have the headroom to run that much light. I'm half way through the 2nd week of flower. I can't really afford to fry my plants. That would have to be the last resort in trouble shooting.

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You wont fry your plants if you turn on your light for 2 minutes. The reason I say to check it is I have seen that exact same issue before and its usually the pot. But up to you, good luck.

@klx ok right I thought you meant run them at fall blast going forward & see if the problem re-occurs. But it sounds like you are saying wait for the problem to re-occur, power down & cut the pot & then power back on.

Sorry I understand now. I hope that is the issue as that is a cheap fix. I actually have a couple of spare potentiometers so I will just replace the pot to cover all bases.

I was hoping this had happened before to someone who may be able to chime in. Thanks @klx

How would the driver or pot cause only two of four leds to go out?

1212ham said:

How would the driver or pot cause only two of four leds to go out?

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good question

He says "I’ve had the last 2 cobs in series not light up twice now" so I assume all 4 are in series, if two are not lighting and two are that already is fishy..

Wiring diagram please and thanks

@1212ham not sure but for the cost ofan pot I'll give it a go.

@CannaBruh yes all 4 are in series. The first 2 cobs have been fine, it's the last 2 cobs that I've had the issue with. I'm on a tablet at the moment so wouldn't know how to upload a diagram on this. I can try when I'm next at a desktop.
It's straight foward series. Positive in through the 1st cobs positive, out from its negative & in to the next cobs positive & out through its negative on to the next cob & so on until the wire comes of the last cobs negative which goes to the negative of the driver.

kushedy said:

@1212ham not sure but for the cost ofan pot I'll give it a go.

@CannaBruh yes all 4 are in series. The first 2 cobs have been fine, it's the last 2 cobs that I've had the issue with. I'm on a tablet at the moment so wouldn't know how to upload a diagram on this. I can try when I'm next at a desktop.
It's straight foward series. Positive in through the 1st cobs positive, out from its negative & in to the next cobs positive & out through its negative on to the next cob & so on until the wire comes of the last cobs negative which goes to the negative of the driver.

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Sounds like series wiring but that 2 do not light while two are lit seems funny? Remove the pot to take any dimming fuckery out of the equation seems like a valid move. For the two that are lit to be lit the other two have to be passing current, which is odd that they do not light... have to think on it, kind of stoned.

CannaBruh said:

Sounds like series wiring but that 2 do not light while two are lit seems funny? Remove the pot to take any dimming fuckery out of the equation seems like a valid move. For the two that are lit to be lit the other two have to be passing current, which is odd that they do not light... have to think on it, kind of stoned.

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I agree this is really odd. It reminds me of when I had my Car Audio store about 25 years ago - I had a display setup with two 4 ohm 12" subs wired in series. One day one of them just stopped playing while the other was pounding away. I measured the voice coil with a meter and it was a dead short - 0.1 ohm. Called the manufacturer and they didn't believe me. Finally convinced them to let me send it in, they called me when they got it. The guy cut the dust cap off and the voice coil looked fine - he checked it out with a meter and it was fine. He put a couple hundred watts through it and it played fine. Sent it back to me and I never had another problem with it. Never figured it out.

OP definitely has a short occurring across those two COBs somehow. No way its a dimmer issue.