Need to convert AC monitor to 12v

Thread Starter

trader007

Joined Feb 27, 2010
249
I am looking to run this monitor off 12v. Its a Dell 1908FP 19" Monitor (ultrasharp model)

It will be installed with a touch panel inside a Kiosk, and I want to run the monitor off the computer power supply instead of running an AC wire up to it (seems redundant to have two inverters in the system anyway, not to mention the inverters that run for the monitors backlight)

Basic questions need not be asked. I am fairly savvy with electronics, I just want to make sure I am not missing something. And for the record- I have done this in the past with a TV, but it was obviously doable the way the board was laid out.

My plan is (when I get home tonight) to find what voltage is coming off the primary transformer. I hope to simply remove the transformer and feed in 12vdc where the transformer otherwise would. I plan on leaving the opti-coupler and everything else in place.
IMAG0503.jpg IMAG0504.jpg

Has anyone done anything like this before? Would love some insight.
 

Thread Starter

trader007

Joined Feb 27, 2010
249
It's a switched mode power supply with possibly multiple taps on the secondary side. I don't see how this can work?
well, at least in the tv i did, the secondary side taps were all 12vdc. Yes, multiple taps, but they were all fused together. Obviously just a board design used in many different applications. from there it broke down to 5v and 3.3v as needed.

I was hoping to find the same logic in this board and do the same thing. I know its a SMPS, but after it rectifies the incoming AC voltage, and then transforms that down to 12v (or whatever pressure it goes to), from there is essentially a DC-DC converter. Only when it hits the backlight inverters does it turn back into AC.....
 

Thread Starter

trader007

Joined Feb 27, 2010
249
Well best I can tell the whole secondary side is run off 5v! I don't see 12v anywhere... surprising.

You're right about the details... I get -5v on the output of the transformer... on all pins. even when the unit is off, all outputs are shorted together.

Thing is, they don't seem to be directly bridged anywhere... as all the pins lead to their own trace routes. And because they are negatively biased, it makes me wonder if parts of the board are designed to turn off for specific reasons.

I'm tempted to just try it anyway and see what happens. I have 20a or so on the 5v rails of the computer, so it should power the monitor fine. wish me luck
 

Thread Starter

trader007

Joined Feb 27, 2010
249
So, an outlet strip inside the kiosk, with the computer and monitor plugged into it. Only one cord out the back then. Or, are there other details we don't know?

Ken
the kiosk was custom designed to fit only the computer case. a power strip won't fit, and we are looking for a more elegant solution.

right now, i take apart the computer power supply and add in a power socket i solder right to the switch inside. this works, but i think it would be a lot better to eliminate the ac cable going up to the screen. Would be very cool to just run 5v up there....
 

dan_n_e

Joined Mar 15, 2017
2
Hey i came across this forum when I was looking on doing the same thing with my monitor. So my question ois if you got it working and if so can you give me some pointers on how I should wire it?
 

WBahn

Joined Mar 31, 2012
29,976
I wouldn't hold my breath for a response from a thread that died well over two years ago from a member that hasn't been seen in well over a year.

Far better to start a thread of your own and refer to this one if you think it might be useful to current members trying to assist you.
 

recklessrog

Joined May 23, 2013
985
Hi, why not buy a cheap inverter like the type used in caravans etc, feed it 12volts, out comes your mains supply ac voltage. they are so cheap and could save you from blowing up the tv or computer or both.
 

dan_n_e

Joined Mar 15, 2017
2
Im planing to put it in my campervan and i want it to run stright out of the batteries without a inverter to lower the current ussage.


Hi, why not buy a cheap inverter like the type used in caravans etc, feed it 12volts, out comes your mains supply ac voltage. they are so cheap and could save you from blowing up the tv or computer or both.
 
You could jury rig it, and splice the cord from the monitor power supply into the one that powers the Kiosk PCU.
I think that that would be the safest (for the monitor). Sadly you can't brag about it:(.
A.H.W.
 
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