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Author Topic: HELP - power and control board for CRT monitor  (Read 985 times)

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--james--

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HELP - power and control board for CRT monitor
« on: November 18, 2016, 11:08:05 pm »
Hi,

I've found myself in a bind after losing the control circuit board for my monitor.  I de-cased the monitor to fit it into a cocktail cabinet.  Now that I am done with all the woodworking, I can't find the board anywhere.  I am hoping that some monitor pros can help me find a way to circumvent this part.

I have some high-res pictures of it, and I can see that the board is quite simple.  It has no ICs, and it just holds the buttons for powering on the monitor and bringing up the onscreen menus for CRT adjustment (geometry, etc).  It communicates with the monitor through a 6 wire plug.  2 are for the dual color LED (standby/orange and power/green).  Two connect to ground, one is 5VDC, and the final one is some sort of serial line marked KBD1.  The circuit traces are huge and all of the components are pretty clearly labeled.  I almost think that I can re-create this circuit board if I really need to.  The monitor is a 19" CRT made by LG model M46QCG903X02.  It has only a 15-pin VGA connector for external connection.  Sorry for rambling about the background, but I'll get to the point with my 4 questions.

*1:  Is anyone familiar with this serial protocol that this mini-board uses to talk to the monitor?
It supports 5 buttons - up, down, 1, 2, and power.  The power button only turned it on and off.  The up and down buttons were used to navigate the onscreen menu, and the 1 and 2 buttons were context sensitive, but generally OK and Cancel.  I assume it is some sort of pulse length serial encoding.

*2: Is it possible to control the monitor through other  means?  I am reading about Display Data Channel (DDC) tech that allows a computer to control the monitor through the VGA connection.  I am just going to put it back together and see if I can even get the monitor to power on with no power switch.

*3: Does anyone know of any tools for hooking up a computer serial port to the monitor control.  I am sure it is possible in theory, but I am by no means capable of hacking together a driver to bit bang some unknown protocol.  I am a mechanical engineer, not a circuits guy and I don't even have an oscilloscope.  I am hoping this is some sort of industry standard with some tools existing.  I can certainly do the wiring to hook a serial cable into the monitor control plug, but that's about it.

*4: If I do have to re-create this board, can anyone help me identify the components.  I see there are two transistors.  The have their B (base?) and E (emitter?) pins marked, but I can't intelligently guess their type or polarity.  I see two inductors, but I can't guess the values.  I see 8 resistors with color coding, so I can probably figure these out, but help would still be appreciated.  Finally there are two tiny axial capacitors with markings of some sort, and a slightly larger canister style (electrolytic?) capacitor.  The polarity is marked for the canister capacitor.

Any tips are reference articles would be greatly appreciated.

Best Regards,
James :dunno

--james--

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Re: HELP - power and control board for CRT monitor
« Reply #1 on: November 21, 2016, 04:09:44 pm »
I just had a bit of a breakthrough.

The actual model of the monitor is ViewSonic E790-VSC4D4D.

All of the insides are branded LG, but I guess it was manufactured my LG for ViewSonic.  I am hoping to find a schematic if anyone can help me out.

Cheers,
James

ed12

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Re: HELP - power and control board for CRT monitor
« Reply #2 on: November 21, 2016, 04:18:40 pm »
type this >lg schematics < into google

ed
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--james--

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Re: HELP - power and control board for CRT monitor
« Reply #3 on: November 21, 2016, 04:39:00 pm »
I promise, I tried google before I went to the trouble of posting in this forum.