| Peabody <waybackNO584SPAM44@yahoo.com>: Jul 22 01:06PM -0500 Ok, this is the first hands-on update. The TV arrived this morning. I hooked it up to my computer via HDMI (it was, of course, the last HDMI connector I tried) and I get audio. Running the flashlight test, I can see the icons on my desktop and any video I play on the computer. The screen is dark, but as I understand it, passing the flashlight test means the video is working, and it's the backlight that's out. However, the owner brought his paperwork with him, and I found the invoice for the repair done in 2017. He says the symptoms were the same then as now. The invoice says they replaced the main board, #BN94-08076A. They charged $135 for the part. I doubt I could repair the main board, but I think it's still worth taking a look. After all, I don't know that the invoice reflects what they actually did to fix it. And even if it was the main board last time, it could be something else this time. Perhaps it will be obvious when I take the cover off, but it seems to me that one test would be to disconnnect the main board from the power board, and see if the LEDs light up. If they do, then it is the main board that's keeping the LEDs off. If they don't then it's either the power board or the LEDs. But is it possible to test what the voltage should be on the lines driving the LEDs? If the LEDs are in series, then it has to be high enough to drive all of them, so maybe 150V or more. Is that right? What I'm looking for is a way to test whether the power board is working or not. Well maybe the voltages will be printed on the board. In the videos it looks like they might be. I'm just not clear how the LEDs are driven. Are they like the old Christmas tree lights - all in series, so if one burns out they all go dark? Or are they in parallel, or what? Still no success finding a schematic or service manual. |
| "ohg...@gmail.com" <ohger1s@gmail.com>: Jul 22 11:56AM -0700 On Friday, July 22, 2022 at 2:06:13 PM UTC-4, Peabody wrote: > I'm just not clear how the LEDs are driven. Are they like the old > Christmas tree lights - all in series, so if one burns out they all go > dark? Or are they in parallel, or what? In *this* model, they're all in series and it's a one channel LED system - one LED or if one interconnect opens, no light. > Still no success finding a schematic or service manual. Samsung doesn't publish schematics anymore. Just block diagrams and wiring diagrams at best. An easy test on this model is to unplug the harness between the main board and the power supply and plug in the AC. With the main disconnected, the on/off line pull-up resistor will put the power supply into free-run, including the LED drive. If the back light comes on, the main *or* the power supply board is bad. If the LEDs come on, post that and I'll walk you through isolating the main or the power supply. If the LEDs don't come on with the main disconnected and the AC applied which is what I'm confident you'll find, measure between BD9101 (either side) and J858 on the top side of the board near the LED harness. Should be more than 150V-300V (depending on whether this uses 3V or 6V LEDs) there between those jumpers. If it's there or higher, the problem is inside the display - either a bad LED or open interconnect between the LED strips. No voltage or low voltage between those points? Bad power supply. |
| Peabody <waybackNO584SPAM44@yahoo.com>: Jul 22 04:32PM -0500 ohg...@gmail.com says... > comes on, the main *or* the power supply board is bad. > If the LEDs come on, post that and I'll walk you through > isolating the main or the power supply. Ok, so the main board controls the brightness of the LEDs through some kind of PWM signal to the power board. If so, then it seems to me if the LEDs fire up when the main board is disconnected, then the main board is the problem - something is grounding that signal line. It seems the power board has proved it's ok. But it does occur to me that if nothing else on the main board is bad, then you could replace the PWM signal with something coming out of an Arduino. :-) > LED or open interconnect between the LED strips. > No voltage or low voltage between those points? Bad > power supply. Yes, that makes sense. I don't have a lab power supply, but if I could borrow one, it seems another test would be to disconnect the LED strips and reconnect them to a power supply. You could ramp up the voltage to see if the LEDs light up at some point. If they do, then they aren't the problem. If they don't, something is open. |
| legg <legg@nospam.magma.ca>: Jul 22 08:48PM -0400 On Fri, 22 Jul 2022 16:32:10 -0500, Peabody >supply. You could ramp up the voltage to see if the LEDs >light up at some point. If they do, then they aren't the >problem. If they don't, something is open. Just use a voltmeter. DC's good enough for this lamp issue. RL |
| legg <legg@nospam.magma.ca>: Jul 22 11:00AM -0400 On Thu, 21 Jul 2022 15:04:24 -0700, Jeff Liebermann <jeffl@cruzio.com> wrote: >>bending something. It will also offer test points for >>measurement. >>RL You're right. It looks like only Panasonoc, Sanyo and Sony sets have a side-button power-on reset. For Samsung audio/no image symptoms, the 'troubleshooting tree' branches out as -check LVDS connector -change tcon -change main board Not very helpful. Unlikely it's a power supply issue, but bulging caps are common, even so, on sets of this era. Some TVs are too smart for their own good. Haven't had one for personal use since 1978. Bloody waste of time. RL |
| Peabody <waybackNO584SPAM44@yahoo.com>: Jul 23 08:26AM -0500 ohg...@gmail.com says... > In *this* model, they're all in series and it's a one > channel LED system - one LED or if one interconnect > opens, no light. On the ShopJimmy page for this model, it shows the LED package as seven strips of eight LEDs, plus seven strips of five LEDs. That's 91 LEDs. If they're all in series, then 3V LEDs would need 273V. So perhaps the strips are wired in some parallel configuration? I'm starting on the diagnostics this morning with a neighbor who I discovered used to work for TI back in the day. One of the ShopJimmy videos say flatly that if you pass the flashlight test, with audio, then a dark screen is either the power board or the LEDs. I guess that's not absolutely always true, but seems logical to me. I'm hoping for the power supply to be the problem. I'm not sure I would be willing to tackle the LEDs. I've watched those videos, and it's a major undertaking, with lots of opportunities to break things. |
| Adrian Caspersz <email@here.invalid>: Jul 23 02:36PM +0100 On 22/07/2022 03:31, Charles Lucas wrote: > https://www.samsung.com/ca/support/model/UN55HU6840FXZC/ > Click on the Manuals and downloads link on the menu selection you can choose > from. Unlikely :( -- Adrian C |
| Peabody <waybackNO584SPAM44@yahoo.com>: Jul 23 11:33AM -0500 Well, I had a major setback trying to diagnose the repair. Last night I set it on the dining room table, face down, and this morning I did the flashlight and audio test again before even taking the back cover off, just to confirm the video and audio were still working. But after about 30 minutes, the TV started working again. All the backlights came on, and the picture is perfect. This is the behavior the owner reported - it might get backlight at any time, or it might not. I measured 267V between BD9101 and J858, so that's the benchmark in case it dies again. So I don't know how you diagnose anything when it's working properly. We tried tapping on every part and connector on the power board, but not even a flicker in the lights. Both sides of the power board look perfect - not a hint of a bad solder, no domed capacitors, no brown marks. The connector to the LEDs (CLN802) has 7 black wires and one blue wire, and a legend that doesn't seem to match the connector. In any case, I will let it cool down, and see how it powers up. I guess I could remove and test all the electrolytics, but there are a lot of them. Same for the diodes. But it seems it could be anything. Major bummer that it's working. :-) |
| Hubert Aubin <hubertaubin5678@gmail.com>: Jul 23 04:08AM -0700 Hello all..my American audio MCD 510 will not read Cds Will not read Cds therefore not play...on both CD player..the CDs turn ...also when remote is connected the eject buttons on base will not work but it does when the remote is not connected. Could it be a faulty remote cable? |
| "Peter W." <peterwieck33@gmail.com>: Jul 23 07:20AM -0700 > Hello all..my American audio MCD 510 will not read Cds > Will not read Cds therefore not play...on both CD player..the CDs turn ...also when remote is connected the eject buttons on base will not work but it does when the remote is not connected. Could it be a faulty remote cable? Are both decks not working? Did this happen all at once? |
| Adrian Caspersz <email@here.invalid>: Jul 22 07:55PM +0100 On 22/07/2022 03:50, Charles Lucas wrote: > A frequent responder here asked me about my motives for coming on here and posting my remarks on a use net post. So, I thought I would answer that question. Charles, You are new to this. Can you find a proper Usenet client and service? Some are free, respond back if you need pointers. Necroposting is a waste of peoples time, and is likely to get you killfiled, flammed or ignored. Many block google-groups for that display of inaneness you've shown answering dead posts. It's bad netiquette. If you must use google groups (and it is a poor display of tech ability if you can't even work that out) then please check the posting date of what you are (probably wasting our) time replying to. -- Adrian C |
| Trevor Wilson <trevor@rageaudio.com.au>: Jul 23 05:56AM +1000 On 22/07/2022 12:50 pm, Charles Lucas wrote: > God Bless and have a great day. > sincerely, > Charles Lucas **There is no "God". Such a mythical creature violates several of the fundamental laws that govern our universe. Any person claiming some kind of technical/scientific credentials who clings to such a delusion is suspect. I suggest you do one of two things: * Seek help for your obviously delusional problems. * Keep very quiet about your delusions. -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
| legg <legg@nospam.magma.ca>: Jul 22 05:08PM -0400 On Thu, 21 Jul 2022 19:50:26 -0700 (PDT), Charles Lucas >God Bless and have a great day. >sincerely, >Charles Lucas No harm, no foul. Ignore anything that's irrelevent. Effective text communication is harder than people think, but with good reading and comprehension skills, it can be the most accurate, in technical subjects (where a phone call can be a waste of time). Though it's harder to bullshit in text coms, it's still possible - anything without references should be taken with a grain of salt. RL |
| Jeff Liebermann <jeffl@cruzio.com>: Jul 22 05:35PM -0700 On Thu, 21 Jul 2022 19:50:26 -0700 (PDT), Charles Lucas >A frequent responder here asked me about my motives for coming on here and posting my remarks on a use net post. (...) >The intent of these responses is to help others, enjoy these posts, and have the people have working, safe equipment. The intent is to do good and no intent to cause harm. I do this on my own time. I'm more selfish. I used to like reading mystery and detective novels. It was fun trying to organize the clues and determine a likely culprit. Same with troubleshooting electronics. Usually, people who ask questions omit important information, like the model number, paraphrase error messages, inject their own pet theories, and generally make it difficult to analyze. When that happens, I suggest that they reorganize their question into a few simple questions: 1. What problem are you trying to solve? One sentence is sufficient. 2. What do you have to work with? (Maker, model, version number, options, documentation, and general condition). 3. What have you done so far and what happened? (Error messages, fire, smoke, explosion, etc). 4. What is your technical ability level and what test equipment is available? The difficult part is getting accurate information and error messages. For reasons unknown, entering a model number from the back of a TV, or errors from a display, into a computer keyboard without errors is difficult. I frequently resort to interrogating people to get answers to simple questions. Some people will waltz around the obvious culprit, ignore the obvious and confuse descriptions by adding irrelevant drivel. It sometimes seems like I'm trying to fix the owner instead of the device. Prying information out of owners can be frustrating at times, but the results are usually worth the effort. Hint: If you know HOW things work, you can fix anything. -- Jeff Liebermann jeffl@cruzio.com PO Box 272 http://www.LearnByDestroying.com Ben Lomond CA 95005-0272 Skype: JeffLiebermann AE6KS 831-336-2558 |
| Stephen Wolstenholme <steve@easynn.com>: Jul 23 02:23PM +0100 On Sat, 23 Jul 2022 05:56:13 +1000, Trevor Wilson >**There is no "God". Such a mythical creature violates several of the >fundamental laws that govern our universe. Who made the universe? Did it need making or has it always existed? I think we have a problem with dimensions. We only exist in four dimensions so we need a "God" to explain creation which is beyond our limitations. To get back to "electronics", maybe the universe is just a simulation. -- Neural Network Software for Windows http://www.npsnn.com |
| "ohg...@gmail.com" <ohger1s@gmail.com>: Jul 22 10:03AM -0700 On Tuesday, July 19, 2022 at 3:58:55 PM UTC-4, Chris K-Man wrote: > Only problem with this place is that the main electrical drop to the building is right outside my bathroom wall, interfering with FM/AM reception. > Is there anything I can do to alleviate this - putting a noise filter on the radio power cord, etc?? > Right at the frequency of an AM I've been listening to for years, is a loud combination buzz/screeching sound. Most AM noise I've found is worse between 700KHZ - 1MHZ. At my house, the AM is almost unlistenable, and I'm in the middle of a 5 acre lot. What I found by shutting off all breakers and turning them on one by one was several items contributing to the din. I found my outdoor motion sensing light fixtures were causing noise (took them apart and hard wired them then added Honeywell wall dusk to dawn switches), my alarm system (added low value capacitors across all keyboard lines at the panel), but the biggest offender was my wifi router. I took it apart and found the PFC cap bulged and changed it. It cut the noise down but it still generates a racket. |
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