Help! Troubleshooting COB Issue

OK, so I have a DIY light with 2 Bridgelux cobs and 2 1500 ma drivers that was built for me. All of a sudden one cob started blinking. I took the light apart and put a new cob in, same result. I then replaced the driver, same result. I thought maybe I botched the solder job on the new cob, so I ordered a cob that was already soldered. Same result.

So, of course this is driving me nuts. I completed took the light apart and broke out all the components. I have the good cob that runs fine when connected to either driver. Meaning I can swap out the driver for the good cob and it runs great with either. I have it just connected to it's heat sink, the driver, and the plug. It's not mounted or anything. Now, I have 2 cobs that blink. And if I hook either of them up to either driver, they blink on and off.

I don't get it. I know the drivers are good since they power the one cob with no issues. I am certain that the other 2 cobs are good (one is brand new with soldered connections). I have tried everything and it just does not make any sense to me at all.

I really hope to remedy this, but I am at my wits end here. Any suggestions?

idk but it sounds like you have 2 bad cobs if you are certain there is no short in your wiring or grounding wrong some how.

Well, the light was built for me because I don't know much about electrical. Right now nothing is grounded. It's just a driver plugged into a wall and then connected to the cob, which is taped to a heat sink. I am using the same plug wire that works for one, but not the other.

Here is video showing how I am trying to test and troubleshoot this. Here is the working cob:


And here is the blinking cob with the same driver, cord, etc:

What does the label on the driver say the output is and what is the model of the COB, not just the brand name? Usually blinking is caused by the LEDs having higher voltage requirement than the driver can supply. Looks like a cheap no-name driver. Also they need to be firmly attached to the heat sink with thermal grease or pad. Can't just tape them on there. Maybe you just used the tape for the test.

The new cob is a Vero 29, the old cob was a bridgelux v22 4000k 6000 lumen. Here is a shot of the driver:

It's a JHX 50 watt driver.

I guess it's just too close to the driver's maximum output. When you first start a Vero 29 the voltage is higher than when it warms up, about 38v. Maybe the specs are off and they really go over 39v. If you parallel wired 2 of the COBs together the voltage would be lower because the current would be cut in half. You'd need 2 COBs on each driver for similar light output though. On the good side, they would be more efficient due to the lower current of 750 ma. They only draw about 36v at that current. You could try it anyway to see if it works or not. Parallel just means the driver is connected to the plus and minus terminals of both COBs at once, instead of them being in a chain.

OK, I tried it. With both cobs connected to one driver, the good cob works and the other does not even blink. When I take the good cob out, the other one blinks as before.

Tstat said:

OK, I tried it. With both cobs connected to one driver, the good cob works and the other does not even blink. When I take the good cob out, the other one blinks as before.

Click to expand...

Okay that's weird then. Maybe they're getting damaged by not good enough heat sink, I don't know. The only other thing I can think of to try is dimming the driver and seeing if at some point in the dimming the COB stays on. You need a potentiometer for that, 100k ohms being best. Actually it doesn't look like that driver is dimmable. Guess you need to get better drivers, ones with dimming in case you need it. Until then you appear to be limited to using the COBs that still work or getting other COBs that require lower voltage. It's good to have a multimeter so you can see how much voltage and current is going into the COB.

Do they need to be glued to the heat sink to work? I think they are just taped on. What about a ground or something? It just doesn't make sense at all. If the driver was crap, why is the other one lighting up fine? It is screwed tight to the heat sink by the lens.

I don't know, maybe I buy a 100 watt driver and try that?

You need heat transfer paste or pad between the COB and heat sink. You can't just screw it on there because there will be microscopic air gaps. That's probably what screwed them up, they got too hot. You can buy the paste at computer supply stores because it's also used for CPU heat sinks. But yeah another driver would be a good idea, preferably Mean Well brand.

Tstat said:

Any suggestions?

Click to expand...

You are right - Usually blinking is caused by the LEDs having higher voltage requirement than the driver can supply.

I guess - it´s one of these chips that you show in your video. ???

Vero 29B- Gen 7
Vero 29C- Gen 7 2700K-6500K

1800mA typical current
1710mA

52.0V typical voltage
69.4V

*************************
Your driver is not bad (97% effic.) and delivers 1500mA @ 20-39V - nor your chips - it`s just the combination.
Always make shure that your driver can reach the requiered voltage of your chip and the
current shouldn`t exceed the max. current.
So this driver you can connect eg. with 50W cob chip 32-36V / 1500mA.
To run your veros you need another driver with above spec. - I guess ???
- just ask your electrician -

Well, the Vero is brand new and has never been run. I bought it from Timber when I got one of their Framework lights last week. And it was pre-soldered.

Something like this might work well, lots of extra voltage. Not dimmable though. They're out of stock right now but maybe somewhere else has them or Mouser might have something similar in stock.

maybe the working cob is a 37v vero 29 and the bad cobs are 52v or 69v version and thats why they dont work on that driver.ask @RainDan what type vero he sent you.

sixstring2112 said:

maybe the working cob is a 37v vero 29 and the bad cobs are 52v or 69v version and thats why they dont work on that driver.ask @RainDan what type vero he sent you.

Click to expand...

Thank you for the bump @sixstring2112

@Tstat I sent you a PM - be happy to assist.

Regards,
Dan

Yeah maybe you got the Gen 7 ones that are around 50v. You need to know the exact model number. If it has markings on the top of the COB (BLX or Bridgelux) it's a Gen 7.

you really need to know which version of the Vero you have as B,C and D are all different voltages and you need to be able to match the driver to the COB
Cheers
Mark

I am trying to figure that out now. I wish I knew more about this so I could speak intelligently about it. All I know is there were the 2 drivers, both 50 watts:

DC25-37v
DC20-39v

I assume the 37 and 39 are the voltage?

And the light worked fine for a while, then it just started blinking. That was a Bridgelux v22. I assume I replaced it with the same chip the first time. And now the Vero type B 52v.

Hi @Tstat,

PM sent.

Thank you,
Dan

I don't see it...