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wrote:

The old CCFL inverter board is too FUBAR to repair. So I decided to use
a couple of cheap 12V dual ccfl inverters (like the kind used for
pc-mods, ect) to power the four backlights.

The power supply board inside the monitor provided the 12v for them to
work and everything works great except...THEY NEVER SWITCH OFF!!!! They
stay on even if the monitor is in standy mode! The only time they shut
off; is if I unplug the monitor from the power source, of coarse.

The connection to the original inverter:
1. VCC (constant 12V)
2. GND
3. ON/OFF (5V) switches to 0V when on standby mode or off
4. DIMMING (2-5V)

The inverters are connected to 1 and 2.

Could someone please give me an idea what to do here. TIA

So you need a transistor to switch them off when wanted.
View in nonproportional font.

| invertor 0v line
|
| o
| |
| 3 R1 | C
| o--[__]--+__/
| | \ npn tr
| R2 | E
| |
| | |
| ---------+---+----o 2

The npn tr must be rated for the current the invertor takes.
Collector goes to the invertors 0v line.
'2' goes to psu connector terminal 2
'3 goes to psu connector terminal 3

R1 and 2 depend on power and beta. Lets say CCFL is 12w max, ie 1A, and
beta min is 30, so we need 1A/30 = 33mA base i to power the tr.
5-0.6 = 4.4v, 33mA - 133 ohms so use 100 ohms for R1.
R2 can be 1mA 0.6v - anything from 560 ohms to 1k.

Adding dimming is a bit more work, but quite doable.

NT