flatron lcd 575lm monitor blinking white screen

[jean luc ferre]

Hello,
for this monitor flatron 575lm when i switch on i have a white screen...
When i connect the vga cable, i have an oscillating white screen, white 2 seconds and then nothing...it doesn't work.
I measured all the voltages on the main board and apparently all was ok...the processor is warming a little...
i have only a multimeter as measuring tools; but no scope. if it needs to program the eeprom i have a ch341a mini programmer.
Is there somebody who could indicate me the manipulations that i could operate to try to solve this problem?
Thank you in advance for your answers.
jean luc ferré

[tom66]

Most common cause of this is a problem with the T-con board, possibly missing voltages or blown fuses

Please post clear pictures of the circuit boards inside the monitor so we can see how they are laid out and what board is doing what function. One picture of the whole back of the monitor showing all the boards, and one of each board, clear and detailed

[jean luc ferre]

Hello,
Thank you for your answer.
i don't see fuse on the device...
Here are the pictures of the elements :
-1: general view of the back
-2: main board
-3: inverter
-4: control panel
i measured the voltages on the main board vga cord connected and it seems me that the 3,3vd was oscillating at the same rythm that the screen was lighted on and off (in white).
when i stopped my pc, the screen lights off...
when i removed the vga cord the screen lights in white...
Waiting for new answer and informations, thank you for all.
Jean Luc Ferré

[tom66]

Clear close up picture of this connector please.

Also, please trace where it goes and show a picture of that board, it is likely the T-CON board.

[jean luc ferre]

Hello,
Thank you for your answer...
Here are the two pictures...
There is not t-con board...the cable goes toward the back of the screen (cf one of the pictures).
i will reconnect all the cables and continue to follow the different signals and voltages...
Thank you for all.
Jean Luc Ferré

[tom66]

Ok, check the voltage across C301 near that connector I highlighted, also, please take the shield off that board and show a photo, need to see if there are any fuses etc.

[jean luc ferre]

Hello,
thank you for your answer.
switching on the monitor and measuring the voltages on the c301 i observed:
- when the vga cable is not plugged i had 3,3v.
- when the vga cable is plugged the 3,3v is oscillating between 3,3 and 0 at the same rythm that the screen ligths on and off in white.
i have allready noted that the signal 3vad (only this one) is oscillating when the vga cord is plugged and that when i stopped the pc (vga cord plugged) the screen lights off...
i have to follow the different signals in order to undestand why the screen is blinking.
i never notices the OSD windows; it seems that the buttons of the control panel are not working.
Thank you for your contribution; waiting for new informations.
Below i inserted the last picture the shield being removed.
Jean Luc Ferré

[jean luc ferre]

hello,
in the few lines below i copied the text that i found on the notice :
DC/ DC Converter
This circuit supplies DC power for each device needing DC voltage of 3.3VD, 3.3V_AD, 3.3V_PL, Module Power 3.3V
and 5VS.
L4973D5.1(U13) , the DC/DC controller IC converts input 12Vdc into 5VS and 3.3Vdc with peripheral circuit
composed of Inductor (L11), condensing components (ZD5, C72), and Regulators(U2, U7, U24,U30).
MODPWR(3.3V) for LCD module power is switched by U12, switching FET, controlled by Microprocessor.
3.3VD, 3.3V_AD, and 3.3V_PL for GMZAN1 (U3) and 3.3V for LVDS (U9) are switched by U5, switching FET,
controlled by Microprocessor for Power saving.
measuring voltages i found that the u12 fet is driven by a signal which came from the microprocesor...and that mong the input signals of this one there is the output of the eeprom .(this last one is not stable) .
i had to examine which signal is acting when i connect the vga cord, because this is responsible of the blinking od the screen.
perhps also, my be a power saving procedure.
waiting for your advices.
jean luc Ferré.

[tom66]

I think you should test all regulators on the main board, you may find a defective one.

[jean luc ferre]

Hello,
thank you for your suggestions...
apart the u30 allthe regulators are ok with correct voltages...
The u30 chip drives the signal modpwr3,3v which is blinking (oscillating) and is connected with the c301 that you recommend me to examine previously.
The u30 chip is driven by the u12 chip where the output signal is oscillating also because the input signal modon is itself corrupted...
this modon signal is coming from the microprocessor.
Below you will find two pictures of image captures relatives to the schématics of these previous signals.
Waiting for more suggestions.
Jean Luc Ferré

[tom66]

Can you link to the full schematic so I can get a better understanding of what is going on.

[jean luc ferre]

hello,
here is the link for the entire document to download :https://elektrotanya.com/lg_flatron_.../download.html
i hope this will help you...presently i am examining the signals coming from and to the microprocessor...but i have not a very clear answer.
Waiting for more ideas...
Jean Luc Ferré

[tom66]

Try disconnecting the cable with MODPWR3V3 on it, and see if the voltages are steady. The screen will still be white but we will be able to determine if a regulator is overloaded.

[jean luc ferre]

Hello,
thank you for your answer and suggestion.
i disconnected the J5 cable and that's allways the same thing...when the vga cable is plugged the screen is blinking and the modpwr3v3 voltage is not steady. what happens is not resulting from this j5 connector; the only thing that stays powering the screen are the connectors of tne inverter...
sometimes i noticed that the screen was coming to saving energy mode (amber color of the power indicator)...with a bip signal of disconnecting on my pc.
waiting for your suggestions and thank you for all.
jean luc ferré

[tom66]

Is the VIN voltage on pin 4 of the U12 also changing or is it steady, I think should be 5V?

[jean luc ferre]

hello,
that's allways the same thing that i had previously; on u12 pin4 is effectively at 5v, but all the other pins particularly pin5 are oscillating...
i will do the same thing but this time trying to disconnect the inverter j4 connector...
waiting for new manipulation.
jean luc ferré

[jean luc ferre]

hello,
i have just removed the j4 connector (inverter) but apart that the screen doesn't light i have allways the same thing on the previous signals...
now i think that the screen sometimes is entering in power saving mode...
jean luc ferre

[tom66]

Well, I think the problem originates from the MICOM.

Either the MICOM is detecting something wrong and resetting the system, or the MICOM has bad/corrupted firmware.

There are a couple of communication signals between MICOM and scaler chip (GMZAN1), it is possible that scaler has a problem and MICOM detects this.

I don't have any more suggestions at this time. The problem is likely on the main board (with GMZAN1 and MICOM) but could be difficult to repair without sourcing a new board. For such an old monitor, it would only be worth it for sentimental reasons.

[jean luc ferre]

Hello,
thank you for your answer...
the price of a new board is very expensive.
Searching on the net for the lcd ht15x13-200 i found informations relatives to controler kits (i put below the links). Can i replace the main board nd so on by such controler?
https://www.google.com/search?q=ht15...client=gws-wiz
here is also a capture picture of this page.

[tom66]

Might be possible but that LVDS connector is rare due to the age of the monitor so you'd have to find a kit that supported it.