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Deep dive into Viewsonic VP230mb monitor, needing help

jeff d

Oct 17, 2015
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Oct 17, 2015
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4
Long story short, got one of these monitors which when powers on the logo is displayed (possibly less bright than ideal) after a second or two the backlight goes out. I've chekcked the i2c controlled ADC which is responsible for the bightness signal to the inverter board. The inverter board appears to be working but I really don't know what values the 6 outputs should be.

Power is good, I've recapped the supply which has one output (12V) which is stable, all other power levels are stable and at expected voltages. The video board (the main board) has also had the radial electrolytics replaced, as have a couple smd electrolytics which had questionable ESR values.

The monitor does track the power saving (sleep) of the connected computer, so when computer sleeps monitor goes to power save mode, when computer wakes monitor transitions out of power save mode. I've confirmed signals like hsync and vsync are as expected but without the backlight I can't see an image and I've tried a bright light on the screen.

I have monitored the i2c traffic which controls the AD converter which is responsible for the 0-3V BRICON signal which is what the inverter uses for driving the backlight. I see the message to set ADC the brightness control channel output to 0xF8 (backlight turns on) and then to 0x0A (backlight turns off). I'm just not clear why the backlight is being commanded off.

The LCD panel is a Viewsonic FLC59UXC8V-03 but the only service manual I found is for the 02 version of the LCD panel. The inverter is a HUI-520A HPC-1411A and I don't have any documents on this part.

I don't understand LCD monitor designs so I think I need some help from those who know how this works. I have read the serial EPROM IC and it had data, but I'm not sure if it's good data. I'd like to try a backup if one exists, but I haven't found one on the web. I also don't know if the firmware on the flash IC is working correctly. I could clip that and read if needed but I didn't see any firmware updates. I've also monitored the UART but that was pretty basic info, I don't think I could make changes over serial, but if possible and I had command descriptions I could try. I am not sure if the display is just configured (via settings) for very low brightness but expect it could not be set so low to make the screen unviewable. The only way to reset is via the menu so that's not an option.
 

Bluejets

Oct 5, 2014
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Oct 5, 2014
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7,050
Shine a torch across the black screen and see if conventional images can be seen.
If so, look at backlight itself, whether LED or fluro type for bad connections to the tubes or dodgy driver board.
 

jeff d

Oct 17, 2015
4
Joined
Oct 17, 2015
Messages
4
Shine a torch across the black screen and see if conventional images can be seen.
If so, look at backlight itself, whether LED or fluro type for bad connections to the tubes or dodgy driver board.
Thanks, I know what you're describing and I've tried but because it's disassembled and face down I haven't been able to get a view of anything.

I know nothing about how the inverter works so that's a big black hole. but I did see voltages in the several hundred to >1kV range but they're only on for 2 seconds. These are fluorescent tubes but given they're drive with high AC voltages I don't really have an easy way to test 'em.
 

Bluejets

Oct 5, 2014
7,050
Joined
Oct 5, 2014
Messages
7,050
Check a few youtube videos on the subject, they can be much more helpful than we can describe in a few words here.
 
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