Backlights work perfectly. They never go out. "Mouse" function works on screen before the screen goes blank. Thinking maybe its Tcon but I haven't fixed a TV in a few years outside of board swaps.
[URL]https://youtu.be/keY2528ysn4[/URL]https://Backlights work perfectly.Th...2528ysn4[/URL]
bscottjohnston
Senior Member
Last Activity: 08-02-2024, 07:43 AM
Joined: 08-05-2023
Location: Denver, CO
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2020 LG 75UM8070PUA 4K problem
Opinion time - anyone ever fix one of these? I just fluxed and reflowed the BGA along with some thermal epoxy on the heatsink for the logic/motherboard and the issue is still the same (refer to video attached). Anyone think this is worth the gamble buying the complete board kit from SJ? $125 gets me a PSU, Tcon and Main/Logic. "Mouse" control works on screen until the crash. Would you gamble?
[url]https://www.shopjimmy.com/lg-75um8070pua-busylor-complete-led-tv-repair-parts-kit/[/url]https://Opinion time - anyone ever f...BGA along with... -
I think its possible you only probed the top set of pins. There are 16 total. The top 8 are easy to get to via the pins going into the board. That said the 29V measurements should probably be 12V since that's what's marked...Also - pin 6 is the standby Voltage and while I am no expert I believe it should be higher than zero.Leave a comment:
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Interesting - I assume that the main board is a problem. Do you have any documentation on why this happens? Is the eMMC storage simply corrupted? Is there a way to repair using software over Ethernet or USB?Leave a comment:
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Didn't see any text in the reply. So as stated the TV now shuts down after 15-20 seconds. All of my Voltages are present at the backlights and the input to the main/logic board. However, I don't "see" them unless the TV is "on". Red power LED stays lit on the shell of the TV. Very odd indeed. Works "fine" up until it shuts down. Don't feel any excessively hot components on the main board. This TV might be a junker unless I can get this main/logic board workingLeave a comment:
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I think that is true too. But I cannot source the relay so I sent the entire board out for repairLeave a comment:
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It was indeed easy to remove and was fairly easy to diagnose to a degree. However, I cannot find the relay here in the US and didn't want to mess with it. I don't want to recycle this one as its huge, looks great and is extremely heavy.Leave a comment:
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These TVs are like whackamole. Inverter fixed the no video problem. Now the TV shuts down after about 10 seconds of use. But will come back on when power is pushed. Thermistor somewhere?Leave a comment:
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What Voltages do you have on this connector while the TV is plugged in but off?
[ATTACH=JSON]{"data-align":"none","data-size":"full","data-attachmentid":3220158}[/ATTACH]...Leave a comment:
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This TV is too huge and too expensive. I have decided to go with a repair service on eBay while I continue to teach myself SMPS circuits. Thanks for all the opinions here. I did indeed learn something even though its been 30 years since I left Navy electronics school.Leave a comment:
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Vizio M55-E0 won't power on - fuse intact
Vizio PSLL241206M inside an M55-E0.
Here's an odd one. Why in the world do I have 76 VAC on the fuse when I have measured 115 VAC on the input power cord? Does this point to something known or simply another SMPS problem I need to run down?... -
This YouTube is pretty good. I'm learning a ton tonight. One thing I am noticing, since I have a shorted MOV near the positive lead of both of my bridge rectifiers, they appear to be wasted. You might have to desolder them to test them correctly outside the circuit.
[url]https://www.youtube.com/watch?v=K-oNaQvMQco[/url]https://This YouTube is pretty good....e the circuit.Leave a comment:
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This MOV reads .86 MegaOhms in circuit. I have other PS boards that work with MOVs that are wide open this close to the fuse. Is close to 1 MegaOhm a defect? I have to think it is without any Voltage applied.
[ATTACH=JSON]{"data-align":"none","data-size":"full","data-attachmentid":3219752}[/ATTACH]...Leave a comment:
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I am working a similar problem on an 80" Sharp set. The fine folks here recommended I build a dim bulb tester to avoid blowing fuses. The schematic might be on the back of the power supply believe it or not.Leave a comment:
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Holy Cow - this dim bulb tester is brilliant. What a great way to work on power supplies without roaching them. Heading to my Home Despot today to grab parts and build. Thanks all.Leave a comment:
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Okay so here's a question for the experts. RL7001 on the back of the board (HF12FF marked on the relay package) is showing 300 Ohms or so on the relay coil but short across the switch contact. The datasheet for HF12FF doesn't show if its normally open or normally closed. The icon on the backside of the board shows open. It just so happens its adjacent to NTC7001 that gave off a small flash when I did my "fuse testing". Anyone have specific knowledge or experience with this part? [ATTACH=JSON]{"alt":"Click image for larger version Name:\tHF12FF.png Views:\t0 Size:\t1.15...
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It would appear as though some sort of schematic is on the back of the board. Is it safe to assume that these boards are single layer? Sorry for the DQs - I did avionics in the Navy but never at a board level. [ATTACH=JSON]{"data-align":"none","data-size":"full","data-attachmentid":3218652}[/ATTACH]...
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I am afraid I don't understand what you mean. I perceive you mean "check the AC_DET test point and see if its lo or hi" but I am not sure where to do that......Leave a comment:
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Sharp LC-80UQ17U Power Supply Board problem
I just picked up a Sharp LC-80UQ17U here in Denver on Craig's. The previous owner said he was watching it and "pop" it stopped. Opened it up to find a blown fuse on the high Voltage side of the PS. I bypassed it with a 7.5 Ampere automotive fuse and saw a flash in component NTC7001 (as the fuse popped). I am not going to try to apply any more power to the board until I can locate a schematic. Does anyone have the schematics to RUNTKB217WJQZ?
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As you mention, pulling the power harness to the main logic board does make the backlights come on.
Putting it all back together and then pulling the input ribbon to the TCON does the same thing. Ordered a TCON on eBay last night.
Do you still want photos? Happy to provide if someone wants them for reference....Leave a comment:
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