Re: LED Driver board Question
I also found 5 resistors in parallel for thermal dissipation.
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Re: LED Driver board Question
Yes, I understand. But the bit I'm curious about is why there are two different resistor values. The circuit will see the effective resistance of the two resistors in parallel.
I have two options here:
1. Buy exact replacements for the two resistors in the circuit.
2. Use slightly higher resistance to reduce the current through the circuit.Leave a comment:
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Re: LED Driver board Question
For fine adjustment of the voltage on the bars and implicitly of the current flowing through the LEDs. The values of the resistors differ depending on the type of LEDs, their typical current and the number of LEDs.
Low value of resistors / higher voltage on LEDs.Last edited by yokoono; 08-11-2020, 02:02 AM.Leave a comment:
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LED Driver board Question
Hi there,
I have been given a store display panel to fix, The output of the B20N15D MOSFETs are fed to the output connector through parallel two resistors, which 2R00 (2ohm) and one R330 (0.33ohm), giving effective resistance of 0.28ohm. Both of these are open and need to be replaced. I replaced both temporarily with a 2R2 resistor and the TV works fine.
I could understand why you would have two resistors of the same value (so as to increase the power you can carry), but I just don't understand why you would have two resistors in parallel with such differing values. Surely most of the current just passes through the R330 resistor and almost nothing passes through the 2R00 resistor.
Is there something I'm missing? thanksAttached Files -
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Vizio e601i-A3 - Has Sound and Display, But No Backlight - Bad Power Supply Board or Bad LED Bulbs ?I was given this TV from my great uncle. He said it just wouldn't turn on one day out of nowhere, replaced the TV, and gave it to me to possibly fix and use for myself.
Upon bringing it home and plugging it up, it showed a standby light.
I powered it on and without a flashlight, the display showed the "V" but the lighting is very dim, but visible.
The screen seems to blackout and stay black, but with a flashlight I can see the display.
With my Playstation 4 connected via HDMI, and running a game I can hear sound.
Assuming... -
Hi, this is my personal laptop, which the original board (lets call it Board A) blew up PU8700 (TPS51486), making a hole on the board, i had left the laptop at my desk one day with the battery fully charged and didn't touch it for a week, but when i tried to turn it on it didn't
Thought the battery was dead, so i plugged in the charger then tried to power on, the power LED blinked once, charged LED still orange, unplugged the charger, plugged in again and I noticed the "magic smoke" smell, so i unplugged the charger, removed the back cover and saw the blown IC (the "magic... -
Working on a 2023 M3 A2992 unit with 820-02918 board, and it uses a new USB-C power architecture, with rectangular controllers. I do not have a perfect-matching board, so have been repairing this one the old-fashioned way (slowly).
I managed to blow-away a single resistor that I can't find and can't determine the value of. It connects to ground, so I went ahead and stuffed it with a 100K resistor in case it's a simple pull-up. But, I'm now having issues with that side of the board, and am curious if it's possibly related to this resistor! I have no schematics and no board view, so... -
Elco (?) 50" Smart TV. Backlight ( BL) issue.
Single Board : TP.SK708D.PC821
I bought new BL set . - OK
Power up : Blip . Protection.
Led Tester shows current at 34.2 mA , Previously it was 42.1 mA
Solution : Change current output .
The BL IC is marked on the photo and datasheet is QOB33535 Datasheet(PDF) - Schneider Electric (alldatasheet.com)
Calculating according to the datasheet - see attached photo :
With ILed = 34.2mA , equation #1 is RFb = 400mV / 34.2 = 11.7 Ohm , and with 42.1 mA we get 9.50 Ohm . i.e I should look for 9.5 Ohm...06-09-2024, 12:25 PM -
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....
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