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Old 02-18-2021, 02:15 PM   #1
mzb
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Default Need help hooking up LED back light strips.

Hi all, I am new here and a novice.I have got the LED strips from china and I am ready to install.
I just want to hook this setup with your help. Please see the photos of POWER board and LED board.
Is it ok to connect the red cable from LED Board to the POWER board's DIODE
with 19V.
Is 19V ok or do I have to use STEP DOWN board to drop from 19 to 12V.
There are no marking on this POWER BOARD, so
I want to know where to connect those 2 yellow wire coming from LED board.
Presumable it should be connected to those YELLOW and WHITE points on the
POWER BOARD. Is there any polarity issue with this?
What about the INVERTOR on the POWER BOARD. Does it has to be disable,
if yes then how?
What other modification I have to do to the POWER BOARD or LOGIC Board?
Please have a look at the Boards.
Thanks.
Attached Images
File Type: jpg DELl..jpg (136.1 KB, 25 views)
File Type: jpg DELL_R~A.jpg (178.6 KB, 18 views)
File Type: jpg USBLIGHT.jpg (12.6 KB, 25 views)
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Old 02-18-2021, 06:39 PM   #2
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Smile Re: Need help hooking up LED back light strips.

Hi mzb,

Fyi, i had done led retrofit on my Acer 1717 with success but my led board is different model from yours. On my led board, the red wire is marked VIN( this is for vcc positive 12 to 19vdc), the next wire is yellow marked EN(means enable backlight need about 3vdc when power switch is on), the third yellow is DIM( to adjust brightness), the last black wire is GND(hook to ground). My Acer model is easier to install since all the markings are clearly imprinted on the power output connector to the logic board.
Not sure if your board has those printed.

Btw, the safer option is to do your voltage checking with your dmm. Verify the proper dc you need then do the solder to that particular point. The most vital voltage is the enable backlight point (about 3vdc for the second yellow wire ) needed to activate the led board.
My tip is to solder a small temporary wire extended about 2 cm from each potential power point before doing the final solder. It is also easier to do the voltage check and solder to the related wire and less damage to the original board.
Do update us on your progress.
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Old 02-19-2021, 11:14 AM   #3
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Default Re: Need help hooking up LED back light strips.

Hi there, thank you very much for your encouraging reply. Unfortunately regarding VIN, DIM and GND nothing is printed on the board, but please have a look at the board, I have written various colors of wires and voltages in OFF/ON condition. You will also see all the voltages at different points on the Power Board. I would do as you suggested, but I want to know is, whether to disable inverter, or leave it as it is. If the inverter has to be disable, then how ?
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Old 02-19-2021, 06:42 PM   #4
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Smile Re: Need help hooking up LED back light strips.

Hi mzb,

The red cable from my led board was supplied with 16.8vdc which i connected to a positive side of capacitor. In your setup you may connect to either diode(in your picture is 15.6vdc) or any one of those cap(positive side) as long as the voltage is between 12 to 19vdc. The first yellow cable(nearest to red cable) you may want to connect to that connector point where you got 2.67vdc when power is switched on. I hope this works to activate the led board.

Regarding the inverter, you may leave it as it is. It does not affect the function of your led board. If you get anxious about leaving those backlight connector exposed since the inverter is on, you may trace back where the inverter connection power source is from and cut off that part. Likely it is one of those jumper wire near the inverter.
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Old 02-20-2021, 09:34 AM   #5
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Default Re: Need help hooking up LED back light strips.

Hi, thank you for your support and reply. One last question, would it be beneficial to use Buck Converter to reduce 16.5Volts to regulated 12Volts or it does not matter.
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Old 02-20-2021, 06:55 PM   #6
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Smile Re: Need help hooking up LED back light strips.

Hi mzb,

The 16.5vdc should be fine as the power supply for red cable on your led board. I think the buck converter is not needed in this setup.
Recheck the voltage point before your final install and just make sure that the power source does not jump up to exceed 19vdc after power is switched on.
Hope this setup is a success and do share us a picture of your new led retrofit monitor.
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Old 02-25-2021, 10:09 AM   #7
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Default Re: Need help hooking up LED back light strips.

Hi there, I am sorry to reply to you so late. I am having all sorts of problem installing the back lights. Although the new LEDs are getting about 18v but they are not as bright as it should be, and in one strip the last 2 led are brighter than the rest, but immediately after these there is one with faint glow and rest of them are glowing but not as bright as it should be.
Could it be the LEDs are not getting enough amps.Should I chose another point for voltage.
The another mistake I did not to record the sequence of those polarized sheets behind the screen.
If anybody could help me in this, I will appreciate very much. Tlhanks.
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Old 02-25-2021, 11:24 AM   #8
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Default Re: Need help hooking up LED back light strips.

I just checked the LED Strips individually they light uniformly but not bright. I am tapping positive from Capacitor drawing 17.6 volts. I have checked my connection and soldering. They seems ok. I do not know what the problem is.
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Old 02-25-2021, 07:54 PM   #9
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Smile Re: Need help hooking up LED back light strips.

Hi mzb,

The 17.6v should be able to run the two led strips adequately. If the led strips are not glowing evenly at the other end, you may want to try to do some resoldering work.
There is a suggestion to solder the cable connector of positive(red) at the positive end of your led strip and the negative (black) at the negative end of your strip so that the dc voltage will be shared evenly among the leds. Scratch the copper track a bit for your solder
to stick firmly on the pad but do this at your own risk not to overheat too much or the led may get damaged.

Have you tried to test run your monitor to see how bright it is after installing the 0.2/0.3 cm thick white acrylic reflector, and also about 3 pieces of polarizing sheets (the middle piece is usually reflective). Sorry i cannot remember the sequence of those polarizing sheets as i use a masking tape to hold them and put aside while working on other area. Wipe away any finger print or oily marks gently with a dry lint free cloth or use plastic hand glove to handle those sheets. Hope this helps.
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Old 02-25-2021, 10:54 PM   #10
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Default Re: Need help hooking up LED back light strips.

Did you get any paper works that come with the LED driver board and the LED strip?
That LED driver board (constant current power supply) has the boost converter circuit that boost the 12VDC input to higher Voltage that is at least equal or higher than the Vf of the LED strip for the LEDs to light up properly with constant current.
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Old 02-26-2021, 08:36 AM   #11
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Default Re: Need help hooking up LED back light strips.

Hi, thanks for your reply. First "Have you tried to test run your monitor to see how bright", yes I did, and saw the only 2 LEDs which were shining bright at the end were illuminating that part of the screen, rest of the screen was not.

Then "There is a suggestion to solder the cable connector of positive(red) at the positive end of your led strip and the negative (black)", this is not clear to me. Do I have to resolder the Red and Black wires to the LED strips ? That means removing the heat shrink and resolder.

"Did you get any paper works that come with the LED driver board and the LED strip?" No paper came with it. I have already raised this issue with the supplier and without hesitation he has agreed to refund the money although I offered him to replace it with a tested, working strips combination.

There is a point on the board where the voltages are 20V, I tried that but the result was the same.
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Old 02-26-2021, 09:06 PM   #12
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Smile Re: Need help hooking up LED back light strips.

Hi mzb,

If there are only two leds are shining bright instead of the whole led strip, i suspect the led strip is faulty. You can test if the whole led strip is working by using a dc voltage of 3v to 6v(preferably a battery pack) by lightly touching your positive and negative dc supply to a group of three led in series. Test the rest of the leds in group of three. If all the leds are lighting, then the fault could be your led driver.
Since you are in contact with the supplier, maybe you can raise your issues and questions on how to install the led setup. Otherwise either get a new working replacement unit or worst case scenario get back your refund.
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Old 02-27-2021, 08:44 AM   #13
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Default Re: Need help hooking up LED back light strips.

Hi mikey, thanks for your reply.
You said "If there are only two leds are shining bright instead of the whole led strip, i suspect the led strip is faulty." All the LEDs are working, except the 2 top LEDs which are shining brighter then the rest(see ONE) when both strips are connected. When only the strip which shining bright is connected, the 3rd LED also glow but not as bright(see THREE).
When both strips are connected, the brightness also differ slightly, say 100 and 80.
The input and the output voltages at the header is the same. on the driver board.
I even disconnected the DIM wire with no effect.
Thanks again.
Attached Images
File Type: jpg ONE.jpg (12.6 KB, 9 views)
File Type: jpg TWO.jpg (6.6 KB, 6 views)
File Type: jpg THREE.jpg (8.2 KB, 4 views)
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Old 02-27-2021, 06:33 PM   #14
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Default Re: Need help hooking up LED back light strips.

Hi mzb,

Looks like the dc voltage is not shared evenly among the two led strips. If you are feeling a bit adventurous and risk taking, you might want to remove the heat shrink from one end of the led and do some resoldering work. I am just suggesting you to solder the red positive cable to the positive side of the led end and the black negative cable to the negative side of the led end. Be sure you got the polarity correct before final soldering. You are doing this at your own risk and definitely will void the supplier warranty.

Last edited by mikey5791; 02-27-2021 at 06:35 PM.. Reason: Black cable is negative
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Old 02-27-2021, 07:34 PM   #15
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Default Re: Need help hooking up LED back light strips.

Did you order a KIT with driver board and led's or did you order the parts separately?
Is this the board? https://eastern-star.en.made-in-chin...d-ES-155-.html
Or is this the kit? https://www.ebay.com/itm/Universal-L...0AAOSwK9heGU~u


It's hard to tell from theses China sites. If it is this board for driving led's, it's output is only 9~10v?

Last edited by R_J; 02-27-2021 at 08:19 PM..
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Old 02-28-2021, 07:46 AM   #16
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Default Re: Need help hooking up LED back light strips.

Hi R_J, thanks for your reply. I ordered the kit from "AliExpress ZBLED Bars Store". I am attaching the photo. The seller has refunded the money immediately so I am free to reorder the kit. But wondering would I get the right one this time.
Hi mikey, now that I have been refunded the money, I will certainly resolder the red and black wires to the strips. See what happens.
I do not know the electronic very much, but what baffles me is that I am getting the same voltage which are injected into the board and getting the same voltages at the other ends, which are more than 12v.
But if 12v are injected directly from other source to these LEDS they shine fine.
People must have encountered such problem before. Is it possible to repair this board ?
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Old 03-01-2021, 03:18 PM   #17
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Default Re: Need help hooking up LED back light strips.

"It's hard to tell from theses China sites. If it is this board for driving led's, it's output is only 9~10v?[/QUOTE]"

Hi R_J, I injected voltages from 6.5 to 9.5 volts. At 7v the strips started glowing and at 9.5v they were shining brightly. I think there is a problem with the board. Any way I have ordered another one.
Thanks for your help anyway.
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Old 03-16-2021, 08:07 PM   #18
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Smile Re: Need help hooking up LED back light strips.

Hi mzb,

Have you installed the led light since you ordered another one set of the led back light kit ?
Maybe you can get more info from the seller on the input voltage requirement so that this time it will work as intended.
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Old 03-17-2021, 11:01 AM   #19
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Default Re: Need help hooking up LED back light strips.

Hi, I just received a new power board from Hongkong, tried it but the result is the same. Without load I am getting 18.6V but after connecting the strips the voltages drops to 6.5v and the result is Screen2. photo. I shortened the first board's voltage regulator (see photo), both strips glue properly and output with load is 8.6 is Screen 1. Either the strips are of the wrong wattage or input voltages should be more. The 18.6v is max. I can get from the power board.
The other problem I am facing is that I am getting all sorts of lines vertical and horizontal and when connected to HDMI cable no picture. There is a chip MAX8795A getting hot on T Con board, I do not know why, may be that is the reason the lines are appearing.
Another problem is that this chip is LQFP and not available in that format, there are plenty QFN format though. The first is 7mmx7mm and the other is 5mmx5mm. I do not know if there is a substitute to this chip.
Attached Images
File Type: jpg screen2.jpg (6.4 KB, 4 views)
File Type: jpg 20210317_144134.jpg (16.3 KB, 5 views)
File Type: jpg screen1.jpg (9.5 KB, 3 views)
File Type: jpg 20210317_151311.jpg (64.5 KB, 6 views)
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Old 03-17-2021, 06:32 PM   #20
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Default Re: Need help hooking up LED back light strips.

Hi mzb,

Got a few general questions before you proceed any further:

1. Is your Dell monitor working normal and display properly without any fault before you start this led conversion project?
2. Any reason why you shorted the voltage regulator on the led board? You may have damaged the board and void the warranty.
3. Refer question No.1. If your monitor was displaying vertical and horizontal lines before or after the led conversion, then you need to solve the lines issue first. Just my 2 penny opinion.
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