Geek pron.

Well, like I mentioned, the MOSFET replacement **** didn’t go over so well. It didn’t do **** to fix the built-in inverter.

So after a bit of figuring, I came up with another solution. The control PCB puts out a signal voltage to switch on the backlight, so it just took a little searching to figure out which pin. Figured that out with a little searching, and found it was 5v on, straight down to 0v off. No need for a pull-down resistor, guess they already planned for that.

I happened to have a MOSFET or two, three, four, laying around, from various failed repair projects. I put one to use switching my case light inverter on and off! You know, that thing that I wired in and switched on/off by crossing wires? Well, I figured the MOSFET could be used.

I wired it right up and it worked right off the bat. The monitor actually switched the backlight on and off like a real monitor, omg!

Well, then came the bad part. The MOSFET was getting a lot hotter than it did during “bench testing” (wired the gate to a pushbumon that was wired to the 12vdc it was switching). It was pretty darn hot. I also found, curiously, that if I tapped on the gate contact with my finger, the screen flickered all the way between off and on (and all brightnesses in between, depending on how light or hard I pushed). Hm.

I found on the datasheet for that MOSFET that the gate voltage being around 4-5v produces pretty much bup**** for current transfer. Well, there’s my ****ing problem. I need to get that 4-5v up to 12v.

So, now, question. I need to get that 5v (4.60v actually) gate voltage up to 12v somehow. I have 4 MOSFETs at my disposal (three significantly more “beefier” than the one I put in – I found those later while looking for one that perhaps wanted a 5v gate level), is it possible, perhaps, to ghetto-rig an intermediate switching level – supply one chip with 12v, gate it with the 5v signal, then signal (gate) the main driver chip with the drain of the “signaling” chip? Come to think of it, that wouldn’t work… far as I understand, those chips work with negatives, and it’s “gated” with a positive voltage. *facepalm*

Perhaps a transistor? I don’t exactly understand the purpose of a transistor, so… *shrug*

edit:

Log in to see images! FalconFour edited this message on 12/10/2008 7:40AM