Re: TCL 75R615 has sound, no backlight
Need the part numbers to know the gate, source and drain. Many videos on how to test.
Need the part numbers to know the gate, source and drain. Many videos on how to test.
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I assume no responsibility for any stupid suggestions I might post. -
Re: TCL 75R615 has sound, no backlight
Ok, so I removed the heatsink that attaches to the two mosfets, I understand this is probably overkill but I wanted to be as throrough as possible. Please see the attached picture with both of the mosfets, I believe thy are MDF18N50, also see the attached link with the data sheet for reference....
https://datasheetspdf.com/pdf/830304...hip/MDF18N50/1
I will attempt to test both of these components per this video......
https://youtu.be/gloikp9t2dAAttached FilesComment
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Re: TCL 75R615 has sound, no backlight
I am still struggling in testing out these two mosfets, Im unable to re-create the testing results using 3 different multimeters I have with diode mode......Im not sure if Im doing something wrong or if there's something specific about these components that would prevent me from using a standard inexpensive multimeter in diode mode to test......any help is much appreciated......
Thanks in advance!!!Comment
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Re: TCL 75R615 has sound, no backlight
I have one of these testers as i do find testing certain parts at times hard
https://www.ebay.co.uk/itm/143173138...YAAOSwPF9ci9rwComment
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Re: TCL 75R615 has sound, no backlight
I maybe wrong here but I think your problem is that your gate to source is 10v to turn on mosfet. Your meter may not be able to do that.Last edited by dskall; 12-08-2021, 10:42 AM.I assume no responsibility for any stupid suggestions I might post.Comment
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Re: TCL 75R615 has sound, no backlight
I kind of thought about that, even though I was not sure.....is it because my meter is powered with a 9v battery it doesnt have enough voltage to trigger the mosfet to turn on/off? I know that description is pretty crude/simple, just trying to understand the concepts.....If that's the case Im guessing i'd need a more powerful DMM or a bench type meter that plugs into the wall? Regardless, Im purchasing one of those cheap LCR tester meters on amazon to try and sort things out.....Comment
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Re: TCL 75R615 has sound, no backlight
I replaced the cap as well as resoldering the heatsink and mosfets. I was too impatient to wait for the LCR meter to arrive. TV seems to power up normally!!! Great news. Thanks to all for the help and advice.Attached FilesComment
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Re: TCL 75R615 has sound, no backlight
Thanks for feedback.I assume no responsibility for any stupid suggestions I might post.Comment
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Re: TCL 75R615 has sound, no backlight
thetonywarren do you happen to have any high resolution photos of the back of the power supply board? My TV recently stopped working and I was able to find some components that were blown related to the 24V main supply. I was able to replace QW401 and R404, but there is a small resistor on the back side (R402) that is part of the gate drive circuit that has a hole blown right through the part marking. Hoping I can find the resistor size in a high resolution image.
Any help you can provide would be appreciated, thanks in advance!Comment
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Re: TCL 75R615 has sound, no backlight
The only pictures I have are the ones from post #3. Other than that, the TV has been working since the repair, use it every day pretty much.Comment
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this tv is throwing me for a loop. do samsung tvs no longer have the backlight self test feature built into the power supply?
i tested the backlight with my LED tester and it lights up both strips. one of them reads 100v and the other reads 63.7v.
unplugged mainboard from power supply but left backlight plugged in, and then plugged psu wall power in. expected to see backlights light up but see nothing.
according to how ive diagnosed in the past, this would almost always be a bad power supply. replacement power supply was cheap like 20$ from ebay. but still i get not even... -
Hello everyone,
Ive got a UE60KU6079 on the workbench that is giving me some headaches trying to troubleshoot.
The previous owner stated that there had been white dots on the screen which from the description sounded like some lenses fell of the backlight LEDs.
He had opened the TV from the back, trying to get to the backlight, supposedly gave up, reassebled everything and gave the TV to me.
I expected the worst like ripped COF cables or a cracked panel but could not find anything like that yet.
Anyway I still fully expect that there has been something seriously damaged... -
TCL 75S421
PSU BOARD: 40-L402H8-PWD1CG
it shows not even a flash of backlight when powering up.
but the tv appeas to turn on and i can hear the sound of the menus moving and clicking. i can power down the tv with the button.
testing the backlights with my tester all 4 strings lit up and showed similar voltage drops. around 110 or so.
unplug mb and leave only psu plugged into backlights (PSU + BL SELF TEST MODE?) does not light the backlights.
i do see 24v but 0v on PSON and BLON (i didnt write this down tho so cant be sure)
with mb connected, PSON... -
Hello all! New to TV repair and trying to bring a TCL 75R615 back from the dead. I've tried to do my basic research/reading but am at a loss so thought I'd see if anyone had some suggestions.
The TV powers up and I can see the backlight on. I can hear sounds by navigating the remote.
I tried disconnecting each side of the LVDS cables one at a time, powering off for a while between, and it didn't change anything. So my first guess was the TCON board so I order a replacement and swap that in. Didn't change anything.
Next I thought I'd try swapping the... -
Hello.
I have an issue with HP 8470p - rather strange one.
I have a noise and sound distortions on both internal speakers and external speakers, when I plug such into the 3.5mm audio jack.
Seems like the noise is present especially when I play audio, where there are parts/sections where the volume of the actual recorded sound is low.
Interestingly, when I play the windows sound test, everything seems to be almost okay. The sound/distortions are similar to when you have interference from some other piece of equipment nearby or when you have an audio receiver with bad amplifier...12-31-2021, 10:25 AM
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