Thread: Problems with screen backlight and allen controller setup

Ok, i had another go at it today. The backlight inverter was definately the problem, cause i tried another inverter, and the screen now lights up fine.

However, i`m still stuck on the problem number 2 (see previous post). I`ve tried different video cards, different computers, but the screen, controller or the connections are definately at the heart of the problem. If anyone has had a similar problem, or know of anything else i could try to get this going.... plz let me know.

Mine makes those patterns when it loses it's signal. When I put it in standby, it'll flash that for a sec before it goes to black. I think it's your cable. :/

Oh, and your avatar scares me

Thanx for the info. I'll check my VGA input cable.... (I have wired in seperate grounds in for the red, green and blue signals, but i have no gounds on the hsych and vsych signals... is this right?). The wierd thing is that the white and blue pattern changes when the computers signal changes... as it boots up (the computer is showing the win98 bootscreen), the screen was loads of white, but when the computer has booted, the lcd shows a lot more blue, so the signal is sort of getting there somehow.

Oh, and don`t worry about my avatar, the face isn`t mine. It`s actually Aphex Twin, who does really wierd electronic music. I can change it if you like.

You probably don't have the hsync or vsync right. Maybe you have them switched or something. Also, pins 5 and 10 on the VGA need to go to the same ground the controller is connected to.

Thanx again 4 the help... I just checked every single pin on my vga/power lead, and everything is at it should be (no shorts, etc.)... heres how i've got it wired:

controller plug - vga plug
pin 1 ----------- pin 5,pin 10 and power ground
pin 2 ----------- power 12v
pin 7 ----------- pin 8
pin 8 ----------- pin 3
pin 9 ----------- pin 7
pin 10 ---------- pin 2
pin 11 ---------- pin 6
pin 12 ---------- pin 1
pin 14 ---------- pin 14
pin 16 ---------- pin 13

Yet it still doesn`t work. This is right isn`t it?

That is correct.

Time to painstakingly check every connection on both the vga cable and your hirose cable

After spending ages checking the vga lead, i found the hirose lead was the problem. Virtually all the connection are in the wrong order, so i`ve now got to spend ages resolding, and getting the order correct. I hope this lot still works when i plug it up properly. Well, at least I found the problem. Thanx again 4 all your help... It`s much appreciated.

The saga continues:
Ok, I spent ages resoldering my hirose lead. I checked it twice, and it is definately correct (connected one to one). I was expecting it to work, so I tested the whole setup again about 2 minutes ago: all i got was a blue screen with a few static stripes for the first second the computer was on. All i got then was a black screen. That`s it. I let the computer boot, still nothing. I checked brightness, etc. but still nothing. So... I have absolutley no clue what the problem is. The only possibility i could think of is that i must have damaged/killed something when i used the incorrectly wired hirose lead. Anyone, plz. help!

Ok, the 5v regulator on the allen controller is fine, I tested it today, but I`m now totally stuck as the spare inverter I was using had to be returned (i borrowed it from a laptop). Anyway, the inverter that I got with the screen (a Computer Dynamics Unidim revision A.02 - datasheet here ) isn`t dead. It outputs zero volts to the screens backlight, and here is why:

The inverter consists of a base board, with all of the connectors and circuitry to do with brightness control. The base board also has a daughterboard piggybacked on it, which does the actual inverting. The daughterboard was 2 inputs from the mainboard... v+ and gnd. The problem is that 12v from the power connector goes straight to the v+ connection on the daughterboard. The ground is meant to have a variable voltage to control the screens brightness, but the never reaches the gnd of the daughterboard, so no high AC voltage is produced (open circuit). I did "cheat" though... I wired +5v and GND from a AT psu straight to the daughterboard. This gave an output voltage of 340V AC (rms i think), but this wasn`t enough to power the screens backlight up, however.

So i have three options here:
1) Make my own variable PSU that outputs between 5volts and 12volts (tricky).
2) Replace the components on the mainboard, and hope the mainboard works and gives the correct voltages to the daughterboard.
3) But a new inverter (no money tho).

Any help appreciated.... I feel like everything's stacked against me here.