Sony Bravia KDL‑40EX520 – Black Screen / HDMI Issue Summary

[rebest]

Problem:

- TV was working fine (via Fire TV Stick) until suddenly the **screen went black**.

- Input source still shows as **HDMI 3**, but no image or audio is displayed.

- Occasionally, **green flickering lines** appear before the screen blanks again.

- HDMI signal is intermittently detected, but no stable display.

 

### What Was Tested & Confirmed Working:

- **Fire TV Stick works perfectly** on another TV.

- **HDMI cables and power adapter are fine**.

- Connecting a **laptop via HDMI** results in the same black screen after brief detection.

- Power cycling, input switching, and factory reset attempts didn’t resolve the issue.

- **TV menus are accessible**, and software update menu opens — but no USB update option appears.

- When playing **built-in demo images or music demo**, the TV works **perfectly** — display and sound function as expected.

 

### Additional Observations:

- TV sometimes **switches HDMI inputs automatically** (e.g. to HDMI 1 on its own).

- **Physical buttons on the TV are unresponsive** (possibly broken).

- When inserting a USB stick, the **USB light turns on**, showing it's detected, but:

  - **No firmware update prompt** appears

  - **No update progress bar** shows

  - TV remains on same screen with no reaction

 

### Firmware Info:

- **Current Firmware Version:** `PKG4.027AAA`

- Attempted firmware file: `sony_tvupdate_2011_4027_aaa_auth.zip` from official sources

- `.pkg` file extracted correctly and placed on FAT32 USB (root folder only)

- Multiple USB drives tried with no success

 

### From Service Menu:

- **Model:** Sony Bravia KDL‑40EX520  

- **Main Board Version:** `DM3.235GAA`  

- **Panel:** `LTY400HM08 01`  

- **Remote Model:** RM-GD020  

- **Software Version:** `PKG4.027AAA`  

- **Region:** India

 

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### Just Want:

**To get the TV working again** — not looking to update firmware unless necessary.  

Any suggestions to revive display output, force HDMI handshake, or trigger recovery are appreciated.

[Sawa Takahashi]

I am not familiar with your exact model but to me it looks like the decoder (or input) board experienced some components failure. The power supply, display and backlight seem to be working ok.

The good news is that a repair shop may be able to get the decoder board and the extra labor should be limited to opening and closing the enclosure.

I don't know the cost of the repair, but you should be able to get an accurate estimate if you simply show your post to the repair shop.

Good luck !

[rebest]

39 minutes ago, Sawa Takahashi said:

I am not familiar with your exact model but to me it looks like the decoder (or input) board experienced some components failure. The power supply, display and backlight seem to be working ok.

The good news is that a repair shop may be able to get the decoder board and the extra labor should be limited to opening and closing the enclosure.

I don't know the cost of the repair, but you should be able to get an accurate estimate if you simply show your post to the repair shop.

Good luck !

Good to hear that, thanks really appreciate it!