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Stu jaxon <stankowalski02@gmail.com>: Nov 10 03:52AM -0800 Hi Group, I have a Samsung TV # un50h6201af has backlight no picture no sound. Power supply has all the normal voltages,. I changed the Tcon board and main logic board, still no pic. I have 12v on both sides of fuse on the Tcon board, still no pic, there are three blue led's lit on the Tcon board. i disconnected the ribbons to the panel one side at a time.. nothing. is the panel bad.???

"Peter W." <peterwieck33@gmail.com>: Nov 10 04:29AM -0800 https://www.youtube.com/watch?v=1MGvkDxajK8   https://www.youtube.com/watch?v=fHhx12Ax7Jk   https://www.youtube.com/watch?v=AvH1ph77Sog   Might help.   Peter Wieck Melrose Park, PA

"ohg...@gmail.com" <ohger1s@gmail.com>: Nov 10 05:00AM -0800 On Tuesday, November 10, 2020 at 6:52:56 AM UTC-5, Stu jaxon wrote: > Hi Group, I have a Samsung TV # un50h6201af has backlight no picture no sound. Power supply has all the normal voltages,. I changed the Tcon board and main logic board, still no pic. I have 12v on both sides of fuse on the Tcon board, still no pic, there are three blue led's lit on the Tcon board. i disconnected the ribbons to the panel one side at a time.. nothing. is the panel bad.???   Unless you bought these boards *brand new* directly from Samsung, you don't know what you're dealing with. Every ebay seller says the board came from a broken screen TV, and that may be true, but a lot of screens are broken when the TV craps and someone throws the remote at it, or simply breaks the screen tossing it on the street or in the recycle pile.   All late model Samsungs are experiencing high failure rates of display screens. Depending on configuration, some will run with half the display connected and some wont, so splitting the screen doesn't always work as a troubleshooting method, although it usually does on the older models that don't usually suffer display failures. Oh, the irony. Check the small brown smd capacitors on the display's address board(s) for shorts. If you find one, you may find a bunch more as they're often massively paralleled. If so, removing the shorted cap will usually restore normal operation. If there is a bunch wired in parallel, look under a bright light and eye loop for one that looks a bit darker than the others. Otherwise, you need to disconnect the ribbons and feed a limited voltage and current into the shorted line and see which cap is warmer than the others. A bit of freeze spray frost layer is helpful.   If no shorts are found, the only way to figure this out is with a scope. You need to check LVDS harness from the main for signals going into the TCON and then out to the ribbons at the display. This is the best method but even that's not foolproof. Some Sony's won't output a signal to the TCON if the TCON doesn't answer the main board's ping on boot...

"ctae...@gmail.com" <ctaestudo@gmail.com>: Nov 10 04:11AM -0800 Hello team   I ask to download these bios below who has access. thank you, Cristian   https://vinafix.com/threads/ih61m-4-2.35664/

David Farber <farberbear.unspam@aol.com>: Nov 09 01:48PM -0800 On 10/18/2020 7:32 PM, David Farber wrote:   > -- > David Farber > Los Osos, CA   Note: The tests I performed below were without the control board connected. The control board is responsible for connecting the earth ground to the audio ground. The schematic of the control board is here: https://cdn.shopify.com/s/files/1/0476/5297/files/80-42000revd25feb10.pdf?2161   The schematic of the main board is here: https://cdn.shopify.com/s/files/1/0476/5297/files/80-42000revd25feb10.pdf?2161   I received the correct parts and installed them. I checked the waveform at the primary side of T2. As I powered it up slowly with the Variac, there was no gradual change in the duty cycle. It was either flat line or full on. I checked the signal across Q802 from drain to source and it was a very clean square wave and measured approximately 400 Vpp. At this point I could reassemble everything and see if it actually will perform properly. But before I do that, I would like to figure out the operation of the power supply circuit that is rectified by diodes D805-D808. It's easy to see that when pin 20 of T3 goes positive, D805 conducts and becomes the V+ line. From that point, it feeds the load and then I imagine it ends up going through ground via the terminal marked HI RAIL on T3 and also through the other ground circuit which is in series with the array of capacitors, C811-812, C849-850, and C34, C36, and C51. Apparently there is also a connection to the bridge circuit, D809-D812. Is there some voltage adding going on there with the secondary transformer windings interacting with the two bridge circuits? This is not a configuration that I have come across before. At the very least I'd like to know where ground is for the V+ supply coming from the cathodes of D805 and D806. I am measuring 90 volts individually across capacitors C850 C852.   Thanks for your reply. -- David Farber Los Osos, CA

Phil Allison <pallison49@gmail.com>: Nov 09 08:06PM -0800 David Farber wrote:   ==================   > As I powered it up slowly with the Variac, > there was no gradual change in the duty cycle. It was either flat line > or full on.   ** Very bad.   Check the 22uF on pin 8 of the PWM IC.   This cap enables the Soft Start circuitry.   https://www.ti.com/lit/ds/symlink/uc3525a.pdf?ts=1604980536419&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FUC3525A   Using a Variac slowly may be an issue, but nothing will happen until the +/- 15V rails appear, then it should ramp up the PWM in about 1 second.     .... Phil

whit3rd <whit3rd@gmail.com>: Nov 09 10:14AM -0800 On Sunday, November 8, 2020 at 12:46:33 AM UTC-8, Andy Burns wrote: > brucek wrote:   > > i'd guess because they are non-sinusoidal outputs and one of the meters is not true rms > I'd say neither of them are true RMS.   Good point--measuring DC current average is the appropriate setting, and there's no DC-scale on any of my meters that does RMS measure.   Voltage, averaged or RMS averaged, is going to deliver at-or-near nonsense numbers for the purposes of evaluating an LED illuminator.

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