Back Light Question
I have a dumpster Dell E151FPb that recapping recently brought back to life. It has a great looking display, nice and bright. I discovered that the brightness control does not change the brightness of the screen. The OSD looks like it is working but the brightness does not change. The contrast works ok. My question is "Do the backlights control the brightness of the display?" If so, how. If not, the how is the brightness controlled? Thanks, Vik.
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Why throw it away? I might need it in the next 40 years.
Duh! -
Re: Back Light Question
The backlights do control the brightness of the display, although this is often not done well. If the connection to the inverter (or the connection between the inverter / power supply and the logic board) is labeled you should see something like Bri, brightness, etc. The voltage on this line controls width of the inverter's output pulse, and thus the brightness of the CCFLs. A quick test - measure the voltage on the control line as you change the brightness setting. If the voltage doesn't change, the problem is with the logic board. If it does, the problem could be with the inverter or the CCFLs are not properly matched to the inverter.Originally posted by MrVik
PlainBillFor a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.
Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic. -
Re: Back Light Question
Thanks Bill for the really fast reply. There are two CCFLs and it looks like they are controlled by a LT1451ACN Pulse Width Modulator. Is this what actually controls the CCFLs? I am attempting to hook everything back up and check the voltages on this chip while pressing the brightness button. Nothing I can find is marked bright, brite, etc. so I am flying blind.
I did take apart an old laptop display to see for myself what a back light was. If anyone is interested, I will make and post the pictures later.Why throw it away? I might need it in the next 40 years. Duh!Comment
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Re: Back Light Question
there are 2 mosfets that often die when the c5706's short.
the number starts with fu.Comment
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Re: Back Light Question
Yep. You can find kits on eBay that have the 4 c5706/07, the 2 FU MOSFETS and a fuse.Originally posted by kc8aduThere are 10 kind of people in this world: those that understand binary, and those who don't.- ASUS ROG Maximus IX Code
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Re: Back Light Question
Thanks for all the great replies! I think we are going to solve this problem.Why throw it away? I might need it in the next 40 years. Duh!Comment
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This happened last Saturday and today I finally had time this morning before I went to work to replace two non brand capacitors
I will let you be the judge weather or not these are bad or not according to the blue ESR meter that I am using
I am comparing them to a brand new one that I installed
The display came back on and the programming was not lost which I was surprised by I would have thought that when the display went blank that so did the memory as well
I going to let it run for several days before I remount back on the wall next to the... -
hi guys, i need your help again...i have tcl u65x9006. while i was watching it become darker like when a movie ends, little by little the image disappear. now if i turn on i have back light on, after like 1 min i have also sound but no picuture. the back light is on i take off one at time the ldvs but nothing change always no picture. i tried to cover with a piece of paper the pin of ldvs i cover like 7 8 pins but nothing worked. the tv stay with no picture. there is a tcon board.i checked the voltage there on the fuse i have 11,8 volts. there is caps in shorts on the exit of the tcon i have... -
Problem
This is an LG edge LED lit LCD Display. The LEDs are on the bottom edge of the display. There are 2 bars (left and right) Each bar has many LEDs and a 6 pin connector. Each pin drive several LEDs thus is the highest current flow / heat junction. The weak lead free solder gradually fails with thermal expansion/contraction cycling and increases resistance. PSU will compensate up to a point, then when the current is too high, PSU just shut down the backlight causing a dark display. I have even seen one which the connector just fell off as solder points became completely detached.... -
Hi All,
I need some help with this one please. I am attempting a repair on the backlight. TV turns on and flashes the LG logo so stripped it down and found one faulty LED. Replaced it and tested on an LED tester and the strip was good. Put it back onto the PSU and it lasted about 20 seconds before going out again. Same LED had blown. Changed it for another type of SMD one (same voltage) and it seemed fine. Put the TV back together but it was quite dim. Noticed it was in power save mode so turned it off and the screen was bright. Left it on for half an hour only to come back to the... -
I raised the question of whether PWM on the power board "dim" pin would be a reasonable assumption for controlling the backlight of a Philips TV (55put6101/12): https://www.badcaps.net/forum/troubl...d-tv-backlight. I didn't receive any insights there so I went ahead and tried it.
The setup is basically:
Rpi3 hardware PWM → 220 Ohm → NPN transistor → dim pin
Transistor is switching the 3.5 V supply on the power board....
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