Hello 
If you are knowledgeable about electronics, I would like your opinion about my repair!
Background (you can skip this part) :
I often buy broken TVs and repair them when possible so I can sell them to make some money. It's kind of a lottery but chances of a successful repair are actually high. Is it worth it? Mostly not, because most of these TVs are a few years old and does not resell for much more than what I pay for them and the components needed for the repair.
- Most of the time, it's the backlight LEDs strips that needs to be replaced. Quite simple to do, but risk of breaking the LCD panel is high (I never broke one because I'm very careful)
- Sometimes, the worst scenario :(, one of the COFs (chip-on-film) of the LCD panel is burned, this is not fixable except with a costly bonding machine and parts that are impossible to find.
- Sometimes, the best scenario :), I find recent 55+ inch 4K TVs for cheap and the problem is just a single shorted SMD capacitor at the bottom of the LCD panel. With these I can earn 200+ € easy... I wish this scenario happened more frequently
- And sometimes, it's a problem on the power supply board, as is the case I'm going to explain now
Problem and repair
I have this Toshiba FullHD 50" TV that is old and worth almost nothing, I had to replace the backlight strips because a few LEDs were burned, but even with new strips there was still a problem, half of the backlight was very dim compared to the other half.
On this TV, the backlight is made of 2 channels, each with 30 LEDs in series (unknown 3V LEDs), so there was a problem on the power supply board, on the circuit for one of the two backlight channels.
Long story short, after finding a full schematic of this board and testing each components of the backlight channel 1 and comparing measurements to those of channel 2, I found fried components on channel 1 :
- one MOSFET P0920ATF
- one diode SR3150
- and not less than 5 SMD resistors
On the picture below, these are components RL18, RL19, RL21, RL22, RL23, QL11 and DL2 (only look at the red rectangles and arrows, not the green rectangles that are part of the original document)
What I did :
- I didn't have the right MOSFET so I replaced by a 12N50NZ which is the closest equivalent (or so I think) that I had at hand.
- Same for the diode, which I replaced by a SF36G.
- I also replaced the MOSFET and the diode on channel 2, for twinning both channels.
- As I didn't have 0.2 Ohm resistors for replacing RL22/RL23, I took one of RL31/RL32 from channel 2 and used it on channel 1. As I understand it, these are shunt resistors for current measurement for the backlight controller IC, right? I don't understand anything else about these resistors.
- The other 3 resistors RL18, RL19 and RL21 were replaced by same values but not SMD.
- And lastly (I often do this when possible) I removed one more resistor on each channel, to slightly reduce the LED current (from ~39mA to ~33mA). A counter-measure against planned obsolescence...
This repair works great actually! But you may know already, I'm not good with electronics! When searching equivalent components by comparing datasheets, or altering the value of a resistance like I did with RL22/RL31 because I had no other choice, I have almost no idea what I'm doing 
Things I noticed :
- I could have used 5x 1 Ohm resistors in parallel to make a 0.2 Ohm resistor (right?), but all I have are through-hole resistors and there is not much room on the power supply board
- The original diode is a Schottky and my replacement diode is not
My question is, did I do something wrong that could damage the power supply, or the LEDs, in the long run ?
Datasheets:
-
Original components :
- MOSFET P0920ATF : https://cdn.datasheetspdf.com/pdf-down/P/0/9/P0920ATF-NIKO-SEM.pdf
- Diode SR3150 : https://cdn.datasheetspdf.com/pdf-down/S/R/3/SR320-HORNBY.pdf
-
Replacement components :
-
LED driver OB3372 : https://cdn.datasheetspdf.com/pdf-down/O/B/3/OB3372-On-Bright.pdf
Service manual of this TV (see around page 54) : https://data2.manualslib.com/pdf7/160/15939/1593821-toshiba/50l2333d.pdf?2da8f4ce86df8539be7feaf65f514d68
The result of the repair ( not my finest soldering, but it's hidden )
