HLG240H 48B drivers stopped dimming

Hi guys,

I need some help with this driver. I have two kits from KingBright of QB288s. Each kit comes with a heatsink, this driver, 2 x qb288 boards and a potentiometer. Plus all wires and connectors.

I assembled one kit and the potentiometer was working perfect. However because KingBright does not seem to care that there are no holes on their heatsink to mount the driver I have had to build an aluminium frame to mount all together.

After I mounted everything on the frame and started testing the potentiometer did not work. The lights just stayed at their highest brightness consuming 265W. With the potentiometer working the lowest was about 20W and the highest was 265W.

At first I thought I just broke something in the potentiometer while putting all together so I took another potentiometer from the second kit to test. I did not mount it on the frame first and just swapped dimming wires coming from the driver to the second potentiometer. With the second one dimming started working.

So I thought that the first potentiometer was faulty and I put the second one instead of it. After I assembled everything again the second potentiometer stopped working too. It does not exactly the same as the first one staying at this highest 265W and it does not react on me turning its knob.

After I tried to test with the driver from another kit neither of these two potentiometers was working at all.

Actually the both lights will turn on and stay at their highest 265W consumption even if I do not connect any potentiometer.

Both potentiometers seems to work when I test them with a multimeter.

It looks to me now that both potentiometers are ok but now there is something wrong with each driver. Even though dimming worked initially on either of this driver now it is not working.

I am not really good with electrical stuff, only basic things but considering that both drivers turn lights on even with dimming wires not connected to anything make me scratch my head. Looks like they became shortened inside the driver and simply do not react to a potentiometer.

Any ideas of what can be wrong?

I can leave with the boards getting 265W but I'd rather try to fix it so I can control the brightness .

I forgot to say that KingBright supplied this type of a potentiometer

https://www.ebay.com.au/itm/2pcs-RV24YN-20S-B104-100K-Ohm-Carbon-Film-Rotary-Taper-Potentiometer-Resistor/120915397786?hash=item1c271e8c9a:g:KfcAAOSwixtXQw7m:rk:1:pf:1

PinPin said:

Hi guys,

I need some help with this driver. I have two kits from KingBright of QB288s. Each kit comes with a heatsink, this driver, 2 x qb288 boards and a potentiometer. Plus all wires and connectors.

I assembled one kit and the potentiometer was working perfect. However because KingBright does not seem to care that there are no holes on their heatsink to mount the driver I have had to build an aluminium frame to mount all together.

After I mounted everything on the frame and started testing the potentiometer did not work. The lights just stayed at their highest brightness consuming 265W. With the potentiometer working the lowest was about 20W and the highest was 265W.

At first I thought I just broke something in the potentiometer while putting all together so I took another potentiometer from the second kit to test. I did not mount it on the frame first and just swapped dimming wires coming from the driver to the second potentiometer. With the second one dimming started working.

So I thought that the first potentiometer was faulty and I put the second one instead of it. After I assembled everything again the second potentiometer stopped working too. It does not exactly the same as the first one staying at this highest 265W and it does not react on me turning its knob.

After I tried to test with the driver from another kit neither of these two potentiometers was working at all.

Actually the both lights will turn on and stay at their highest 265W consumption even if I do not connect any potentiometer.

Both potentiometers seems to work when I test them with a multimeter.

It looks to me now that both potentiometers are ok but now there is something wrong with each driver. Even though dimming worked initially on either of this driver now it is not working.

I am not really good with electrical stuff, only basic things but considering that both drivers turn lights on even with dimming wires not connected to anything make me scratch my head. Looks like they became shortened inside the driver and simply do not react to a potentiometer.

Any ideas of what can be wrong?

I can leave with the boards getting 265W but I'd rather try to fix it so I can control the brightness .

Click to expand...

Open dim +/- wire leads will result in full power draw. I can only assume you maybe pinned the wires to the pot wrong when you installed it? Maybe you got flip flopped and had to turn it around for the install and didn't account for the wires needing flipped too?

It has been all fixed and both lights are dimming now.

My friend who is an expert in electronics suggests that there was bad wires connection in these transparent connectors that are used to connect two wires together. It is a bit of strange but after getting wires in and out of these connectors many times I got like 2-3 times in a row when the pots worked and then 2-3 times in row when they did not.

I have attached the pictures with the light attached to the frame I have made. There is no pot shown but you can see the hole on a flat bar on the right side of the driver where the pot is supposed to go. Need to do extra holes at the corners for hanging and I am done with that .

It is shame KingBright did not even care of making the heatsink bigger for the driver to be fixed on top or at least provide some holes on it for the driver to be screwed into it.

Forgot to ask, can anyone tell me if it is safe for the wires touching the heatsink. Since I have never run it for a long time I have no idea how hot the heatsink can get. I am just thinking it can get too hot and it will start melting insulation on wires.

Also does the driver itself can heat up to quite a hot temperature or only QB boards are getting hot transferring their heat to the heatsink.

I am doing a 15 minutes test now and after 5 minutes the heatsink is already +54 degrees C. But may be I cannot call it a not real environment test as my light is standing on its side now and heat can escape upwards while when the light is hung it raises into the heatsink.

After about 20 minutes the heatsink was not getting hotter than 65 degrees C and stayed at this level for 5 minutes. It may be going to change with the right light orientation and hours of running it on but so far it is not bad.

On compression type connections it possible on low voltage/current situations to have enough connection resistance to make things work differently. The cheap carbon deposit potentiometers have the solder terminals "rivetted" to the carbon. I have two quantum's in my veg room that I diy'd and used a cheap 100k pot. If you move the wires the light will increase brightness and or go full on. Poor designed potentiometers. In my flower room I used 4 sealed wirewound pots. Old design. I need to update my veg pot or one day it will fry my seedlings. I'm not saying the pot in your situation is poor quality. Just that on low voltage/current situations connections are critical. Some of the equipment I've worked on years ago had "high fidelity" relays and or contacts. Very low closed resistance.

We checked the driver diagram and my friend told me that for dimming to work it should be from 1 to 10V. Then he asked me to add a 9v battery to a circuit and told me how to connect it all together.

The idea was to check that pots were actually working even though my multimeter said they were ok. After I did the test with the battery which proved the pots were working I removed the battery from the circuit and dimming started working. So I guess it was actually connector-wire combination that sometimes made the whole circuit working at maximum as the wires were not sitting properly inside these connectors.

I may be just solder the dimming wires directly to each pot pins one day just to make sure I am not dealing with the connector faults.

PinPin said:

We checked the driver diagram and my friend told me that for dimming to work it should be from 1 to 10V. Then he asked me to add a 9v battery to a circuit and told me how to connect it all together.

The idea was to check that pots were actually working even though my multimeter said they were ok. After I did the test with the battery which proved the pots were working I removed the battery from the circuit and dimming started working. So I guess it was actually connector-wire combination that sometimes made the whole circuit working at maximum as the wires were not sitting properly inside these connectors.

I may be just solder the dimming wires directly to each pot pins one day just to make sure I am not dealing with the connector faults.

Click to expand...

Wait... you hadn't soldered the dimming lead wires directly to the potentiometer in the first place? That's gotta be done with these. Too small of a tab to do anything other than solder.

No I did not solder because each pot came with two wires soldered to it. Then by using supplied connectors they were supposed to be joined with the driver dimming wires via these connectors.

However soldering dimming wires directly to the pot pins will do a better job and it will eliminate any problems with these connectors.

I am not really good at soldering small things but these(wires and pins)are quite big and when I have time I will be able to solder the dimming wires directly to the pot pins.

I have built the second frame today, put it on the heatsink and everything works including the pot. Need to add hooks or rings for hanging ropes and they will be ready to go into my cabinet.

These lights are so bright that just a quick look at one set with 576 diodes even at some big angle put a ghost image in my head with the diodes matrix for one minute. I do not even need to close my eyes to see it. I guess with two sets and over 1152 of them is going to be even worse. Definitely need some glasses for eyes protection with these lights.

PinPin said:

It is shame KingBright did not even care of making the heatsink bigger for the driver to be fixed on top or at least provide some holes on it for the driver to be screwed into it.

Click to expand...

Thats because mounting anything on top of it will alter the thermal dissipation that the sink was designed to disperse.
You could get a hot spot that expands and shrinks the circuit board at a different rate,causing cracking over long term use.
They did the right thing, take notes.
You need to to get those AC connections inside a box, grounded to the frame if you go with metal vs PVC.
Every time you plug it in or raise the light, its going to pull at those wires.
That is a lot of faith to put into a 2 cent ty-wrap on the AC side, don't become homeless for lack of $2 and another hour labor.
Get 2, for AC and DC connectors and mount it on the bar you have the POT on, mount the POT on the cover plate of the DC side

What about HLG lights? They supply their lights with a driver mounted on a heatsink. It does not look like they consider it an issue.

As for connectors and tightening wires I am going to do it. I want to replace KingBright connectors for AC wires with a normal black one. It should make at least this part safer as it will be easier to manage one straight cable if it is not bent two times with these original connectors.

PinPin said:

What about HLG lights? They supply their lights with a driver mounted on a heatsink. It does not look like they consider it an issue.

Click to expand...

If they did it , then they tested it and engineered it. Probably isn't an issue
KingBright either did not designed for it or not mill the heatsink for it, probably both.
I like where you have it mounted, it stiffens the frame,has clearance for cooling and makes it easier to service, not being attached to another component.