Researched a bit into floating gate (Both NOR and NAND flash memory cell use floating gate mechanism to storage bits) Found this video that provides a simple explanation of floating gate. Its basically through trapped electrons.
Sounds like floating gate will loose charge over time (and at high temperature) so some people suggest to "recharge" them every couple of years ( link ) Perhaps thats the failure mode of these TCON's NOR flash.
Based on this understanding, I imagine just re-flashing the NOR flash will "recharge" each gate to close to their...
howardc64
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Last Activity: Today, 11:11 PM
Joined: 06-03-2017
Location: Seattle WA
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These ~2015 Vizios has main board BGA solder ball cracking problems (same as early to mid 201x 15” MacBook pros and GPUs) Proper fix is remove BGA and reflow with leaded balls. Most people don’t have equipment so just bake in oven / hot air gun (neither will last long) Regardless. Need to know how to handle temperature properly (like not put board on cold garage floor and hot air gun causing board warp and crack)
if hair dryer on main heat sink (for awhile to get it nice and taasty) can revive tv then this is the problem.Last edited by howardc64; Yesterday, 06:19 PM.Leave a comment:
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Insignia NS-43D420NA20 backlight on no display - LCD panel burn failure
Eventually discovered a burn mark near lower corner of LCD. Here is a summary
- Backlight on, no image
- Disconnect right buffer board (view from front), left side display comes on
- Masked off pin 7+8 (both ~12,5v on both left and right buffer board) from t-con to right buffer board (view from front) display works but have some lines
- Buffer board is pretty simple
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Probably need to investigate deeper on which signals pins are masked to gain further insight of the failure. Check service manual repository link (type "Samsung QN" into search box) if your main to t-con flex is similar to the QN55Q6DRAF service manual (pg 5-7 5-8 along with main board similaries on T-Con flex)...Leave a comment:
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I've not seen this model but since its low end brand (TCL) and Google TV, maybe likely it suffered the eMMC failure so common for Google TVs?
Here is a HiSense Google TV I debugged with this problem ( link )
Nick's TV has a ton of videos on SONY's Google TV with eMMC failure ( link )
Low end brand like HiSense also puts HDCP, Netflix and streaming app keys in the dead eMMC so even if new eMMC is firmware installed. Still lost all keys so streaming and HDMI won't work. SONY was smart enough to put the security keys in separate memory.
If replacement...Last edited by howardc64; 07-09-2025, 09:14 PM.Leave a comment:
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Did a bit more testing. Seems like this older slower Tizen just require a bit of patience.- First turn on the TV, apps menu pop up on bottom. But in reality, app system is just setting up and network getting connected. Need to wait until this menu disappears before popping it up again to launch apps. If earlier (like when it first pops up which invites user to launch the app) will get either wait for system to setup msg or the network not connected msg.
- Sometimes apps hang and unfortunately older Tizen has no "quit" app mechanism. Go back to home screen, switch to a none steaming
Last edited by howardc64; 07-09-2025, 07:43 PM.Leave a comment:
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Samsung UN55JU650DF network/streaming problem
Fixed a 9 year old UN55JU650 by replacing backlight. Original backlight LED was still working after 27k! hours but terrible picture of course. Few LEDs were out, 5-6 lens fell off (bright white spots) and another few popped off with slightest force. Surviving LEDs were all slightly blue so picture has a blue tint.
This TV runs older Tizen OS (updated to latest version, see pic) and have problems with network (wifi or ethernet) connection. The Tizen UI frequently switch to coax input source while changing content sources. . If no good signal (coax not connected, no prior antenna/cable...Last edited by howardc64; 07-09-2025, 02:10 PM. -
google 303HK500048 shows all russian sites and alibaba high volume sales. post #2 aliexpress listings are all 303HK500040. Don't know if same replacement or similar.
Next search step probably involves cross referencing. One Russian site said this is for Haier H50K6UG. Unfortunately Google H50K6UG LED strip didn't find anything. Any look through the Russian sites and see if can find other model #s to search....Leave a comment:
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Samsung UN65NU6950 edge lit TV LED bar after 10k usage hours
Edge lit LED TV has 1/4 section backlight out. Replaced the LED bars and sharing the findings on the original 10k hour LED bar.
These are 6V LEDS (reads ~5.4+ on my LED tester) New bars read about 147V per 1/2 of each bar. Clearly original LED bar has some problems- One section is 153v with a dead LED so clearly built up resistance
- One section flickers but magically fixed itself after driving individual LEDs. All done with an LED tester so don't know if would work driven by PSU backlight circuit and how long it would last
- Connector pin to test pad resistance is nearly 0 ohms.
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very good summary. Another variable is any high heat solder connections thermal cycle weakening over time. I fixed about 20 apple 27 thunderbolt displays by reflowing ithe edge lit LED bar connector. Original lead free solder weakened and resistance increase push PSU beyond its limits. On this TV I haven’t disassembled to know what the led system looks like.
I guess Samsung firmware updates (default auto update) made it much worse by disabling dimming or even any ability to adjust backlight to lower brightness....Leave a comment:
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Probed all pins between PSU and LED driver board
pin 4 = Vdrv On = 3.067v
pin 7,8,15,16,20,21,22 = GND = -0.011v
pin 9,10,11,12,13,14 = Vdrv = 69v
pin 17 = B13V = 12.83v
pin 19 = FB = 2.139v
FB signal looks like goes through side B of the LV358G op amp (IC 280), then to the main board connector (CN 250) and the Samsung chip nearest that connector (IC 2100)Leave a comment:
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Yes, I always avoid max brightness on LED TVs. 6V LEDs (typical TCLs) seems more easy to fail.
On this TV, I wonder why have 69v instead of ~64v printed on the PSU. Maybe printed # is wrong. Maybe LED driver baord is requesting higher current which should show higher voltage if resistance path doesn't change?
But PSU LED + - isn't final individual mini LED current on this zoned mini LED TV design. So I wonder why driver board needs to request more current from the PSU? Anyway, still trying to understand the design.
LED driver board does have a feedback signal...Last edited by howardc64; 07-05-2025, 03:39 PM.Leave a comment:
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Looks like many Samsung mini LED backlight TV owners are struggling with local dimming not working. Some owners (gamers?) dislike local dimming so I wonder if Samsung may have turn it off as default in a way that no one can easily turn back on in recent firmware updates.
Tried lowering PWM_INI_2D and PWM_MOVIE_INI (both 100 default with latest firmware) to 20, no difference with youtube dimming/black screen test videos. Did find someone posting their SubSetting menu (in service menu) and a couple of differences from mine- Mine has no PWM_MIN
- My 2D_DimPosi1 is 2x bigger. Didn't
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yes of course. Just did this to test until replacement part arrive.
I don’t know this diode would cause 69v instead of ~64v spec printed on the PSU. Don’t fully understand the circuit. The 4 diode’s anode are on the PSU <-> driver board ground plane. Also I’ve seen wrong voltages printed on PSUs before although this board prints 1/10 volt resolution.
Will go through service menu in detail. Other Samsung’s have settings for lower backlight level....Leave a comment:
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UPDATE : Got the backlight to turn on...
Studied the circuit of the shorted barrier diode rectifier array. There are 2 arrays (2x 150V 20A diode in each array) with total of 4x 150V 20A diode working in parallel. Since only 1 diode failed, I guessed 3x parallel is reasonable design margin to test the TV. Cut the shorted diode leg and TV backlight turns on.
Now I notice likely the original problem. LED driver voltage is 69V while the board has printed ~64V with up arrow. I also notice its 69V constant regardless of content brightness. Ran black video and...Last edited by howardc64; 07-05-2025, 02:04 AM.Leave a comment:
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Yes, as noted in post #1, this TV had prior repair attempt by Samsung. What they did is unclear but I guess they likely changed the PSU and failed again after working 1 hour. So have suspicion downstream hardware (LED driver board, mini LED array) has fault that is causing PSU to fail quickly.
Anyway, so far LED driver board have no evidence of clear fault so I will probably just repair PSU shorted diode soon to start testing....Last edited by howardc64; 07-04-2025, 08:54 PM.Leave a comment:
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The shorted diode is labled #2 in post #1 underside PSU picture (#4 pic) Its a 2x barrier rectifier diode array rated at 150V 40A. I've extracted the component and confirmed 1 shorted diode. Will order replacement soon.
The mini LED array wiring circuit is mysterious to me. I have seen older larger LED zoned backlight flex on SONY 65" XBR TV, it seems to use matrixed addressing method (line to send row and column data) to reduce wire/trace count. So multiple LED brightness controls are multiplexed over a single wire to reduce wire numbers. On this TV, this is surely...Last edited by howardc64; 07-04-2025, 02:32 PM.Leave a comment:
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I'm not expert but looks like 4 layer board? Tracing 1 ground path on the mini LED connector cap disppears on both side of the board so surely > 2 layers.
...Leave a comment:
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Someone send me following info why a cap might be connected to ground on both ends. Largely to reduce high frequency noise on one ground plane from contaminating another.
So if the LEDs brightness are adjusted by PWM the ground, this would have some frequency component. Maybe conecting a cap to a very low frequency ground is helpful? My background is not an EE or even board design engineer ( software and digital computer architecture )
So maybe those mini LED connector ground cap is properly designed...
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⚡ Reasons to Connect a Capacitor...Leave a comment:
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Yes fuse Y has continuity on the 13V rail.
Also checked the power rails into the LED driver board from PSU. 64V LED power rails goes directly (0.5 ohms which is just probe resistance) to all the mini LED connector (pin 4-6, 46-48 on 51 pin connector) after 8R2 2213 inductor. I guess the 5x Samsung chips probably modulate LED current (and therefore brightness) via PWM ground or variable resistance.
Ground pins (7,8,15,16,20,21,22) from PSU are the only pins with continuity to board ground.
Board seems good other than the shorted cap (remained shorted when...Last edited by howardc64; 07-04-2025, 10:47 AM.Leave a comment:
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