UE40D5700 bootloop overnight

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fl3sk
Posts: 2
Joined: Mon Sep 05, 2016 9:14 pm

UE40D5700 bootloop overnight

Post by fl3sk »

Hi guys,

my TV died overnight, probably due to OTA updates, I'm not sure. Did not touch the service menu, micom update stuff or something like that.
It does immediately power on when AC is connected, does not react to any keys and - unfortunately - I'm not even able to enter the service menu.
One or two years ago, I gained root access using the SamyGo Smart Hub method, but I was not using it lately. Not sure if this is helpful.

I tried an EEPROM reset as described in the wiki https://wiki.samygo.tv/index.php5/UnBri ... PROM_Reset. Shorted SDA and HRESET for some time (see pic), the TV did stay on longer, powered off later. The screen now does not show "HDMI1" (last used source) anymore, just a blank screen after that. So it did something, but the bootloop didn't stop.
d5700-eeprom-small.jpg
I'm now trying to get something useful out of the on-board UART console, which I found on CN801_DB (1=GND, 2=TX, 3=RX, 4=5V, TX/RX 3.3V levels).
d5700-uart-small.jpg
Parameters are 115200 8N1 as usual. Unfortunately, I only get:

Code: Select all

Hello UART
and some garbage. I tried to enter the TDM codes (https://wiki.samygo.tv/index.php5/Top_Debug_Menu:_TDM) here, but no success.
Any ideas on how to get that UART running? I think I can't enable ExLink because I can't enter the service menu. Perhaps it's possible to find the physical UART wires similar to here https://forum.samygo.tv/viewtopic.php?t=4049#p31473?

I'd like to get access to the bootloader or something similar to reflash exe.img. I already downloaded and decrypted it using the SamyGo Firmware Patcher, now I'm looking for a way to flash it. I'm also thinking about desoldering the I?C EEPROM and erasing it using an Raspberry Pi, but I don't know if that will be of any use.

Any advice, guys? I'm currently lost.
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fl3sk
Posts: 2
Joined: Mon Sep 05, 2016 9:14 pm

Re: UE40D5700 bootloop overnight

Post by fl3sk »

Did some more testing of the power supply. Voltages seem correct and stable.
If I disconnect the BLE on/off (Backlight enable) pin, the backlight stays on permanently. However, the board still reboots.

Is there any possibility to re-flash the firmware via usb as some part of a failsafe process? I suspect damage in the internal ROM.
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erdem_ua
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Location: Istanbul, Turkey
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Re: UE40D5700 bootloop overnight

Post by erdem_ua »

It looks like OTA kills the device. Probably new firmware found that devices program is altered/rooted and this leads boot loop.
I don't think if resetting eeprom will fix the issue. Because the firmware decide to reboot.

I believe re-program the NAND will repair the TV but don't know/remember how to do it in this state of the TV.
You better to start searching some used mainboard for your TV.

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