Viewsonic VG2230wm backlight flashes when no signal - even if powered off

[emailjunk2me]

I acquired three VG2230wm monitors which were malfunctioning or not working. I have repaired two by replacing bad caps.

The third works when it is fed an input signal. When the PC is shut down or goes to sleep the backlight flashed rapidly. It flashes even if turned off via the power button.

The power board is a Delta DAC-19M009AF if that helps. Any ideas on what the problem might be?

Thanks,

Vince:

[stj]

Re: Viewsonic VG2230wm backlight flashes when no signal - even if powered off

i saw something like this once.
does it use a seperate invertor, or is it on the psu?

the prblem i saw was a transistor controlling the BL-ON signal was leaky and turning itself on.
the result was the backlights never turned off.

[emailjunk2me]

Re: Viewsonic VG2230wm backlight flashes when no signal - even if powered off

The inverter and power board are integrated.

I was kind of thinking it might be something other than a capacitor....

I have attached a pic of the board, if that helps...

Vince

[stj]

Re: Viewsonic VG2230wm backlight flashes when no signal - even if powered off

any chance of a better pic of the lower right so i can read the writing next to the vertical board.
also - the other side probably has the controller on it.

[emailjunk2me]

Re: Viewsonic VG2230wm backlight flashes when no signal - even if powered off

Picture of the lower right attached.

Also, I found the schematic, but it has been many years since I read one, so it looks almost foreign to me...

What do you mean by controller?

Thanks for your assistance.

[budm]

Re: Viewsonic VG2230wm backlight flashes when no signal - even if powered off

"What do you mean by controller?' The board which it has the VGA/DVI connector, that board is also plugged into the power supply board.

[bammbammfran]

Re: Viewsonic VG2230wm backlight flashes when no signal - even if powered off

The backlight controller chip that I believe STJ wanted to see is the 20 pin chip under the power board

connect the two boards and plug them in and then see what the voltage is on the pins that connect the two boards together.
the two you want to check are the two that are closest to the center of that side of the board.
one is the dim pin and the other is the on/off pin
the on-off pin might be the one that is pulsing and trying to light the bulbs

[budm]

Re: Viewsonic VG2230wm backlight flashes when no signal - even if powered off

Per your SCH page 35, CN5 pin 15 is the Inverter enable pin (there are labels on the connector) you need to monitor the DC Voltage. <1V = backlights off, >2vdc = backlights on. See if the voltage is bouncing around when you turn off the monitor.
http://s807.photobucket.com/user/bud...?sort=3&page=1
BTW, there are more than one version of this model.

[stj]

Re: Viewsonic VG2230wm backlight flashes when no signal - even if powered off

suspect parts to check:
zd200
q200
q202
q207