Re: LG 42LE7500 TV Backlighting but no Picture
Thank you @tvtimmy for your response. I have seen where people have heated their mainboards in an oven at 380 for ten minutes. What you are saying is to just heat the cpu? Is that the only part that is losing connection? I can do that with my hot air station. Any recommended temperature? I generally run my station at 225 for most things. Thoughts?
bwilliams60
Senior Member
Last Activity: 02-24-2023, 07:45 PM
Joined: 08-11-2014
Location: London, Ontario
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Re: LG 42LE7500 TV Backlighting but no Picture
Here are my pics. I suspect that 20V circuit may be a problem?...Leave a comment:
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Re: LG 42LE7500 TV Backlighting but no Picture
Okay here are the voltages I got with Power Off and then Power On
ON 0.00 VDC 3.25 VDC 20V 0.00 VDC 21.4 VDC
20V 0.00 VDC 21.40 VDC 20V 0.00 VDC 21.4 VDC
GND 0.00 VDC 0.00 VDC GND 0 0
GND 0.00 VDC 0.00 VDC GND 0 0
3.5V 3.48 VDC 3.40 VDC 3.5V 3.3 3.3
3.5V 3.48 VDC 3.40 VDC 3.5V 3.3 3.3
GND 0.00 VDC 0.00 VDC GND 0 0
GND 0.00...Last edited by bwilliams60; 01-31-2020, 09:00 PM.Leave a comment:
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LG 42LE7500 TV Backlighting but no Picture
Good Evening All. I have a 42" LG TV that was given to me and my background is more automotive electronics so was hoping for some direction on this. I can get around the TV okay, just need pointing in the right direction. This TV starts up okay and backlighting comes on with no problem but there is absolutely no picture. I have ran an infrared monitor over the power supply and most areas that I think should get hot, are, but that is obviously no measure of anything so where should I start with this one?
It has two boards in it. Mainboard and Power Supply I am assuming. I don't have... -
Re: RCA 42" LED TV - No picture - RLDED4215A-E
Unit needs new LED strips. Tested each one at 27 volts and bottom row fails.
All good.Last edited by bwilliams60; 10-15-2018, 07:54 PM.Leave a comment:
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Re: RCA 42" LED TV - No picture - RLDED4215A-E
Okay so I found the LED connector and measured it with my DVOM. On Standby, I was measuring -53.3 VDC with my leads in correct orientation. When I turned the TV on, it climbed to 173 VDC and then down to 68 VDC where it stayed after about 15 seconds. No lights. So one would assume that the lights are in fact burnt out. Any thoughts?Leave a comment:
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Re: RCA 42" LED TV - No picture - RLDED4215A-E
Are they not hooked in series across the screen, but in parallel off of the side boards? I haven't opened up the LED portion yet but I would assume that if the backlight is out, that would mean every LED would have to be out. Is there a way to test the whole LED section or do I need special tools.Last edited by bwilliams60; 10-15-2018, 05:46 PM.Leave a comment:
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Re: RCA 42" LED TV - No picture - RLDED4215A-E
If it was one or more LEDs, would I not see a partial screen?
This was like the whole screen went out all at once.Leave a comment:
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RCA 42" LED TV - No picture - RLDED4215A-E
I have this newer LED TV and there is no picture when I turn it on. The blue light comes on but there is absolutely no backlighting. If I flash a light on the screen, I can see the picture in the background. There are only two boards on this when I take the back cover off. I have attached pictures of the unit and the boards. Nothing looks like it got hot and can't find any bad caps, solder joints etc. Any ideas? Thanks in advance... -
Re: FLUKE 179 problems
Thank you to Redwire and Retiredcaps for your help. It was indeed because of that article that I took a closer look. I also noticed on one of the pics I snapped, that the connection didn't look good but I put it off to lighting at first. When I finally checked the pathway, it all made sense. So I took a pick and easily pulled the inductor off the board. I will try it for the next few days before I am convinced that is all there is. For now, a sigh of relief. Simple fixes are best
Leave a comment:
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Re: FLUKE 179 problems
Well I have some good news. I started tracing the circuit from the beginning and found a bad connection between the inductor and the board. Resoldered and now everything seems to be working. I am going to compare it to a couple of other meters just to see how they compare but we are further ahead today then we were yesterday
How would one identify this inductor or put a value to it?
This is the one located very near the fuses.Leave a comment:
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Re: FLUKE 179 problems
Okay here is what I have so far:
Rotary switch fingers are all good.
JC switching diodes appear to be okay but not sure on exact identification. When the single post was to the left (pin 3) and the tow were to the right (pin 2-top and 1-bot), I got the following readings:
3-1 0.00
3-2 0.618
2-3 OL
1-3 0.00
1-2 0.618
2-1 OL
which would indicate to me that 1-3 are connected and go through a diode to 2?
The S1B tests at 0.601 in forward bias and 1.084 in reverse bias
The DF06S tested as follows:...Leave a comment:
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Re: FLUKE 179 problems
1. No probes = O.L.
2. Probes shorted and meter set to ohms = O.L.
3. Measuring a 1k ohm resistor = O.L.
4. Continuity setting/Diode function = O.L....Leave a comment:
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Re: FLUKE 179 problems
Okay here is what I have.
All three varistors read O.L.
The PTC reads 1.095 k Ohms
The resistor measures 1.05 kOhms
The resistor bank = 1M ohms...Leave a comment:
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Re: FLUKE 179 problems
Thank you all for your comments. With respect to the parallel threads, no harm in using resources. I respect all who answer and those who don't, but I see no harm in asking more than one body.
I will test as suggested and I only mentioned the fuses etc to show the state of the unit. As for the state it was in when I got it, just as I have described. It came to me as a dead unit with exactly what you read going on. Prior to that, it had sat in a toolbox for a while. It is a very clean unit.Leave a comment:
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FLUKE 179 problems
Good Evening, I have a Fluke 179 that won't measure resistance at all and the ammeter always reads negative although the amperage seems to be close to accurate. On DCV, measuring a 9VDC battery, it shows 8.34 VDC when connected with proper polarity and -1.328 VDC when reversed.
I am guessing this was connected to voltage when measuring resistance. Does anyone have a schematic or a good place to look on these units. The traces are hard to follow and they are layered and well masked. Looking for guys who have experience with these meters please.
Both fuses have been tested and are in...Last edited by bwilliams60; 09-20-2017, 06:54 PM. -
Re: Samsung 40" LCD Seeing Double
Is this the same as what I said in my first post? Disconnecting one connector cleaned up the screen and showed 1/2 image. Pulling the second connector resulted in double image and horizontal lines. Perhaps you could elaborate on the cut-off technique?
BudM, I will try that and see what happens. I will let you know. thank you....Leave a comment:
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Re: Samsung 40" LCD Seeing Double
Can you elaborate on the reasoning for failed panel?
The unit had an image, I was able to make it singular and now I can still get images but they fade away....
Tab bonds??? Where the ribbon mounts?
Just looking for plausible answer with explanation. I don't like guessing. Any way to wittle this down?Leave a comment:
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Re: Samsung 40" LCD Seeing Double
Well, I think something just blew. I removed the ribbons and cleaned them all up, turned the set back on and no change.
I gently pressed down on the left ribbon and the right side of the TV now has vertical lines on the far right, top to bottom. If the set stays on for a few minutes, the entire picture slowly fades away to a blank screen.
TCON???Leave a comment:
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Re: Samsung 40" LCD Seeing Double
Flexing the panel did nothing for me so I uncoupled the ribbon and then held it down with my finger and the picture came out as it should. Am I replacing the TCON or the ribbon? I am thinking the ribbon.Leave a comment:
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