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Repair guides for displays (or monitors) for computers or other devices with video output.

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Monitor doesn't display but lights up.


  • Monitor: Millenium MD34
  • Panel: Samsung LSM340YP05
  • Control board: MST9835RN-EDP
  • TCON board: CCPD-TC-340-001

I'm trying to repair broken display, the display turns on the backlight and act logical (turn on backlight to display manufacturer logo, turn off to sleep///turn on backlight when plugging signal(HDMI/DisplayPort) and don't sleep) - it doesn't display anything on the screen, it just stays blank. Power board all good. Cleaned flex tapes.

Board controller main IC heats up to ~70-75 celsius w/o heatpad, TCONs heat up to ~50 celsius. No other elements heat - confirmed using Flir thermal camera.

Is the display panel broken in your opinion? I can buy TCON board, Control board or whole monitor with broken display panel - as whole monitor is more expensive I want to ask - TCON, Control board or display?

Should i measure something? DMM, Oscilloscope available.

Best regards,

Update (03/24/23)

Coming with data - I've replaced TCON board and everything acts as it was - I've got another controller as well but it behaves exactly the same. Replaced PSU even the voltages were stable - nothing changed. I'm starting to belive that the matrix itself is broken but have no ideas how to troubleshoot it.


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I didn't attached matrix board thermal photos as nothing lights up. I've checked the voltages tho - there are WINBOND W25Q16JV flash IC's - they work on 3.3 V - on both matrix boards the voltage is present, stable and correct. Checked voltages on chokes - voltages seemed correct. +12V is stable. I tried to measure both matrix boards in form of comparison - results were mirrored so it seems there's nothing wrong on those boards.

Do you have any thoughts or hints what to measure or check? Maybe there is some way to debug/troubleshoot the matrix itself? There's an I2C on controller and MURA on TCON board but I think those are dead ends.


Update (03/27/23)

If the situation is the same your matrix is most likely [99% as all components work] broken.

Mine was.

Answer this question I have this problem too

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@kundro post some pictures of your boards with your Question. That way we can see what you see. Adding images to an existing question


@oldturkey03 I'll provide 4K pictures + thermal pictures tomorrow. Stupid I didn't think of that when I was in my workshop.


@kundro nah, not stupid. It happens and no worries :-)


@oldturkey03 provided photos, br


@kundro so you've replaced the power supply, the main board, the t-con board and still no luck. the only board that you have now left should be the LCD controller board. Give us some good clean close-up on that. I am looking for voltage TP so the closer and clearer the better. Also, give us any number that might be a part number. That way we might find more info.

If you haven't replaced the power supply, do the same thing. Nice clean close up will help. Where did you measure your "stable 12V" voltages?


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Hi @kundro,

You said "...and act logical (turn on backlight to display manufacturer logo,..". Do you mean that the manufacturer's logo is being displayed on startup?

If so then there's nothing wrong with the screen.

If there's no video being displayed regardless of the input type but the logo is being displayed then there's a problem with the digital signal processing circuit on the mainboard.

The logo signal emanates from the software stored on the mainboard eeprom but then it uses the same circuitry to get to the screen via the tcon board as the video signal does after it has been processed by the DSP.

It could be faulty firmware but I can't find any online. You may have better luck

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No. It acts logical because it turn on the backlight when turning on - every monitor displays manufacturer logo on the start - in that moment my backlight act like it should because it turns on for 2-3 seconds and turn off - in that moment status LED starts to blink which indicates sleep mode. In that way I'm sure that basic logic of the board works.



I'm still not sure if the logo is being seen or not as to me your comment is not clear (the backlight is not the logo) but assuming that the "No" at the beginning of your comment above means that the logo is not being displayed, then it could be any one of the 3 components in the video path - mainboard, tcon board and screen.

As @oldturkey03 suggests providing pictures may be the next best step. Perhaps there are voltage references shown somewhere on the board


@jayeff As this was your only question your assumption is correct. I didn't had access to monitor today so I haven't made photos - I've ordered monitor with the same parts inside - the same parts was used by AOC, VIOTEK, Xiaomi, Gigabyte and Millenium - my monitor act exactly like in : - I'll try to replace the TCON board(as monitor works the same with/wo the TCON board) and get back with data.


Added photos as you asked. Jayeff - I think you saw this before in this thread:

Monitor shows blank screen. Backlight works..


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