itelite
Senior Member
Last Activity: 02-14-2025, 08:17 PM
Joined: 08-21-2016
Location: PA
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Ive done a few more of these over the years. When the problem matches that as originally posted, the resistor swap seems to work. The suitable resistor value does seem to vary though. Ive found putting a small potentiometer in the place of the resistor is great to make the fine adjustments to resistance required to get the best picture. You can turn the pot and watch the color saturation change until you get too high or too low of a resistance (causing a reboot). You can then either leave it, or measure the resistance and replace it with a SMD resistor of the same or very close value.... -
Do you get anything at all on VGH? How about with no power cord plugged in, resistance to ground on VGH, and/or diode mode measurement from VGH to ground.
Best place to start would be ruling out a sort to ground, or an open circuit.
in all my test a while ago I recall there always being some kind of measurable voltage on that VGH pin/resistor....Leave a comment:
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That very much sounds like this is the same problem then (if indeed we are talking about putting a wire between the VGH resistor pads or equivalent.)
Im sure you thought of this, but if not, keep your wire as is, and use it to test the various resistor values. That way you don't need to solder anything each time. I think it is just going to be a matter of finding the correct value. Start with a high value and note results. Again, as I'm sure you know, resistors in series will add, and in parallel will divide.
Couldn't hurt to verify resistance with a meter as ... -
When you say "works as expected" do you mean successful, or unsuccessful?
If successful with no color or image artifacts, I would call that a win.
Otherwise
I suppose a decent test would be no resistor at all. That would be equivalent to taping over the VGH pin (or an infinite resistor). If that works (if memory serves, you should get the boot up chime, but no image, but I could be wrong on that. then you know the problem must be on the VGH circuit, at that point I would try a very high resistance like 1Mo. then keep cutting that resistance...Last edited by itelite; 12-21-2023, 07:02 PM.Leave a comment:
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Try to find the VGH pin, and work from there. It should be very similar....Leave a comment:
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My feeling is that you must be doing the mod incorrectly. Everything you are describing suggests that you are having the same problem with the same equipment. Post some high quality pictures of your work. See if we can sort out where it's going wrong. Ive done quite a few of these, and this always works with various resistance values.
Something I've found to be helpful is to use a potentiometer in place of the resistor, that way you can adjust the resistance to see where it boots properly and where is doesn't. Note the results, and you have your tolerance window.
...Leave a comment:
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qn55qn85aaf schematic
bn41-02855d Main board
Feels like a long shot, but any one have the schematic for the main board?
It seems to have a panel short that i cannot find. It feels like it is doing the VGH reboot thing that a few other series of samsung do, but i cannot conclusively locate the VHG pin/line.
It will cycle/reboot forever unless i unplug the ribbon between the panel PCBs. If i plug that ribbon back in while running it will shutdown and begin the cycling with in a few seconds.
Checked every passive on the panel for shorts and got nothing... -
Re: samsung un65nu6900f common problem, digging deeper
Since i wont have it to test on the tv i can probably put on variable resistor that you can turn with a small screwdriver to set the appropriate resistance.Last edited by SMDFlea; 07-05-2023, 10:04 AM.Leave a comment:
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Re: samsung un65nu6900f common problem, digging deeper
If you want to mail it to PA, my shop can do it. PM if interested and we will coordinate....Leave a comment:
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Re: Vizio V585-H11 T-con Mod
Post a picture of your work....Leave a comment:
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Re: samsung un65nu6900f common problem, digging deeper
Just want to add, the same model came in the shop today, i performed the same modification successfully.
The only difference, is i used a 30K resistor to replace the R13246 on the main board. I tried a 10K first and it was not successful. I also tried a 2K and it was not successful. I dont think exact resistance is crucial, but too low the tv will power cycle, too high you will see artifacts on the screen. Presumably from the VGH current being too limited.
No need to do the wire run thing if...Leave a comment:
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Re: samsung un65nu6900f common problem, digging deeper
Good to hear it working. As far as i am aware the original TV in thread is still working fine.Leave a comment:
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Re: Samsung QLED QN70Q6DTAF Dead 2 blinks Flashing Backlight
left hand most if you are standing at the bottom of the tv by the panel bonded board.Leave a comment:
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Re: Samsung QLED QN70Q6DTAF Dead 2 blinks Flashing Backlight
Working on the same tv with the same problem presently in my shop.
Ive isolated the issue to the left most panel board. With that disconnected it will boot up, with it connected it will not.
I have check all components on the panel PCB for shorts to ground and so far all looks normal.
Do you know what pins you covered so far? It could be helpful to know what signal you are covering.
If i figure anything else out of this end i will post.Leave a comment:
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Re: Vizio V585-H11 No Image Puzzle
Puzzle has been solved.
[url]https://www.badcaps.net/forum/showthread.php?p=1166288#post1166288[/url]Re: Vizio V585-H11 No Image Puzzle<b...t1166288[/url]Leave a comment:
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Vizio V585-H11 T-con Mod
Had a V585-H11come in with no picture today. Similar problem to the Samsungs i figured out a few months ago
[url]https://www.badcaps.net/forum/showthread.php?t=107445[/url]
Same solution. I replaced a single 0 ohm resistor on the TCON with 10K ohm. It turned on, has picture, no distortions or artifacts. Looks like R78.
I dont know why this works, but it works.https://Had a V585-H11come in with n... <br /> Same... -
Re: UN70NU6900FXZA power cycle, no picture - workaround found
Interesting. That is not consistent with my prior work. There is no harm in trying a 10K in that resistor spot, but it is a SMD so if you are not comfortable working on the board dont bother.
For future reference, you will typically never want to use resistance mode measurements on a live/active/powered circuit. Best case your reading will be inaccurate, worst case you will blow up your meter and/or damage the device under test. That said, it sounds like your resistor is measuring within spec (as it was...Last edited by itelite; 06-24-2022, 09:47 PM.Leave a comment:
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Re: samsung un65nu6900f common problem, digging deeper
Oh totally. I have a decent sized pile of them at my shop with burn marks all over the diffuser, some cracked, some melted through the back white sheet.
What an absolute mess of a tv design.
I was actually rather sure when i saw the model number this was going to be a burnt up backlight as well. After the fix/mod i turned the backlight very low and advised the owner to keep it there. I usually advise "Keep the backlight as low as you can tolerate". If they ask why, i have a NU...Leave a comment:
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Re: UN70NU6900FXZA power cycle, no picture - workaround found
It is an educated speculation at this point. My success involved running a wire and resistor to bypass the ribbon cable, but in theory the same can be accomplished by replacing that resistor (currently a 10ohm) with a 10k.
Any resistor at all will do, it passes close to no current at all. no harm in pulling one off another electronic device/donor board....Leave a comment:
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Re: UN70NU6900FXZA power cycle, no picture - workaround found
interesting. It really should be 25v when the top ribbon cable is unplugged. At least it was for my measurements and fix. With the cable unplugged that resistor should be 25v going into a 10ohm resistor (will remain 25v), then going no where at all (open). Just to be clear, for your measurement you are putting black probe on a ground point, and red probe on either side of the resistor, correct?
Also can you verify that your resistor actually measures at 10ohm? Your measurements seem impossible...Last edited by itelite; 06-22-2022, 09:16 PM.Leave a comment:
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