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ビデオ出力付きのPC用ディスプレイ(もしくはモニター)の修理ガイド

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Philips BDM4065UC turns on for a moment, then goes dark

My Philips BDM4065UC suddenly stopped working recently. The issue seems to be only the backlight - the USB hub works, the standby light works, the menu joystick correctly resumes from power off, and with a bright flashlight I can see the expected picture on the screen.

When first powering on, the backlight comes on at full strength to show the blue Philips logo, very quickly dims to about half brightness, then shuts off completely. The center row appears to dim more than the edge rows.

Power Board:

Block Image

I’ve disassembled the monitor to attempt a diagnosis. The connection to the mainboard seems fine - the 19V pins all supply ~20.2V, the 5V pins are at ~5.5V, and the ON/OFF and DIM pins have 3.3v on them during operation.

Mainboard pins:

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The LED output pins seem questionable. The pins are labeled LED +V and LED-V, without saying what those voltages should be. There are 4 pins (leading to 4 rows of LEDs), each of which show 11.5V in operation - both during the initial period of backlight ON, and after it shuts off. The return lines are combined, and show some variation - during initial backlight ON period, they show up to 45V (approximately the outgoing voltage for all four LED strips). After the backlight stops working, they show ~30V.

LED pins:

Block Image

Is this a power board issue? Or should I be looking downstream at the LED strips? There was no brightness problems before the sudden onset of this problem, but there is a bit of variation in how the strips behave currently.

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So I have the exact same issue with my BDM4065UC as well! Did you ever find the cause?

I initially thought it was the main board, since the blue Philips logo shows during startup. Thereafter I can sometimes get a stable picture, but then it cuts out. I haven't found any schematics.

I have changed the back light LED strips on my unit, since they where breaking as well. So maybe this is related to this.

Will look at the power supply board, so see if I can find anything strange there..

さんによる

Also having this issue, so what was the problem for you, LED or PSU?

@vespaman

さんによる

The main issue was the LED's alright. Ordered new from ALI express, and got a better monitor than before (higher brightness and lower power consumption). But the picture cut out was related to the DP cable/input, so I changed to the mini/micro(?) DP input with a quality cable. Since then no problem with the monitor at all.

I read somewhere that the DP input on these monitors are not great.

さんによる

I replaced the power board with an AliExpress match, and this did not resolve the issue. I have LED strips waiting for my next try - EXCELLENT to know that your LED replacement worked! Thanks for the update!

さんによる

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Hi @flowmage ,
I don’t know but a quick way to test the backlights without disassembling the screen, is to use a TV backlight tester (supplier example only) to test each backlight strip individually.

Disconnect the LED power cable from the power board and hook up the tester to the cable. It supplies the necessary power for each strip (one at a time) i.e. no power required to be connected to the monitor, so that you can see if there is a problem or not.

If all the strips are OK then you know that the problem is elsewhere.

If the strips are the problem then here’s a link regarding the LED strips for your model that may be of interest

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I can (belatedly) confirm that this behavior was an LED backlight issue. Replacing the backlight strips got my monitor back up and running!

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flowmage さん、ありがとうございました!
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