LED Voltage Issues


New member
Ok, so my led system has been running for 3 years and haven't had a problem. I have been running a 24v system and Steve's drivers but changed to Meanwell LDD Drivers @ 48v. I have been wanting to do it to clean everything up as it is much simpler and everything is together. I have 14 mostly Luxeon LED's on each string. Everything seems great I can dim and ramp like always, but here is the problem. Some LED's on other strings will light dimly when I turn on just 1 string, it doesn't matter which one. So I began testing for shorts, nothing. I have tested each LED probably 50 times and have no continuity to the heatsinks. Even tested the edge of each star to soldier pads, nada. When I plug in the power supply I can measure 47v (where I have it set) from any of the heat sinks to DC ground only on the power supply. I've never tested that before so maybe it's normal? As I ramp up LED's that voltage I can measure goes down and with everything at 100% I can measure around 15v to ground on any heatsink. If I turn on one string, I can actually measure (usually around 9v) of output from the other LDD's even though they aren't on. Any ideas what the heck is going on? Thanks in advance. Sorry for the long post.
Here is a pic of the setup.


Active member
You know when you couple this w/ your Apex converter board it points somewhat to an issue w/ your driver board..

Or a ground leak. Or both.
LDD's when "off" shouldn't measure any voltage on the output. At least as I have found.

Could be your LDD board is touching a ground? (light metal)


New member
Hey Oreo. Thanks for the response. I had to give up on the APEX for now and am just running the Bluefish. Steve's is having me send the controller interface back and sending me another replacement. The LDD board I have rubber bushings to keep it off the canopy so it can't be touching anything.

Now I think I have freaking gremlins. The tank has been 2 days without light so I put the canopy back on and what do you know, it works perfectly. No random LED's lighting up and zero V out of any LDD's that aren't "on". I can still measure ~20v from any heatsink to dc ground with everything off though, better than 47 I guess. Makes absolutely zero sense other than a short(s). I am positive there are no shorts and no wires touching anything anywhere though. I even ran each string before one at a time with all others unhooked from the driver with no change, so that would mean that every string would have to be shorted which isn't the case. This is ALLLL because I got a stupid apex lol. I do love my apex though!


Active member
Hmmm. You seem to be leaking voltage to the entire fixture..
AFAICT heatsinks should be zero volts to dc ground..

If all of them are doing this.. well not good..
Isolate one bar from the light itself.. measure voltage to ground..

If zero.. then one of the power supplies is probably leaking..

Not likely your err fan brick but who knows..
Some odd reason I'm thinking the ballast..

Working "better" w/ it on and closed seems to point to something pulling away by gravity, and not as conductive..

PIA troubleshooting so much stuff..Just need to remove one part at a time I guess..

Only takes one small "short" to energize the entire hood..

Disconnect the ballast from the AC line.
Meter one heatsink and then disconnect each bar from the "out' on the ldd..see if it goes to zero.
If still 20 or whatever reconnect another and disconnect the one..
Measure the re-connected one..

Opps you sort of did that..
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