# Thread: Help, trying to convert AC monitor to use DC.

1. Originally Posted by digitalmayhem
So if I understand correctly, the power is rectified to dc and then converted to two different voltages using the regulators? So I would want to find the voltage after the rectifier and feed it what it wants and let it regulate that current into whatever it needs? Also, if I do F up this board, I can replace it for \$30.
The regulators keep the power from exceeding a certain voltage limit. The transformers are what steps it up/down.

It looks like the transformers are after the rectifier and before the regulators. If true, that means a single DC voltage is supplied and then stepped up/down by the circuitry so you could theoretically feed it a single DC voltage and it would work.

*IF* I am right. Which I may not be.

2. So I do want to check the voltage at where I labeled as "dc out" at the positive and negative terminals?

3. Originally Posted by digitalmayhem
So I do want to check the voltage at where I labeled as "dc out" at the positive and negative terminals?
Start there. If it is 12V you are golden. That is not likely. Chances are it is a fairly high DC voltage so be careful. The clue about that is that the nearby capacitor is only 100uF but at 450V. Be careful not to get your fingers in there, it may bite!

4. It read 165 volts before my dumbass tried to measure the amps and blew the fuse on the board. I'm an idiot.

5. The ammeter creates a short across the leads. It's almost the same as just taking a wire and shorting out two points. Don't do that.
Anyways, here's what I think the different parts are. Everything that I pointed out is an AC component except for the regulator and the rectifier... That I'm thinking that since there are voltage multipliers on the board, that the backlight may run on the AC.

6. See? There you go - I think Arrow may be right. If that's a filter, not a rectifier, then it is AC up to that big capacitor for sure. Looking close at the ~DB50, right near the base of the cap, I think that indicates that you have AC power at that point. Did it read 165 volts AC?

Those big things attached to heat sinks are avalanche diodes, if my googling is correct. They are supposed to protect from over voltages.

With the voltage regulator way up there on the upper right, I think Arrow is right about the backlights being powered some other way - probably AC, which would make running this thing on DC only difficult.

7. D850 is definitely a bridge rectifier. C854 is a filter capacitor. Everything past that uses DC. The backlights need a high voltage and the logic circuits need a low voltage, hence there are at least two regulator circuits. Let's remember the purpose of the OP's question: can the monitor be run on DC if it is put in past the place where it is converted from AC to DC? The answer is yes it can, IF you put 165V in. That is not practical to do in a 12V auto environment.

8. my multimeter was in dc mode. typing from a cell phone.

9. Well, right there you have a problem, then. Since you can't supply 165 volts DC, you're going to have to figure out the various DC voltages you need.

If you need AC to power the inverters, now you're talking about replacing the inverter(s) and CCFL's plus figuring out what voltages you need to operate the monitor.

Going back to your original post, you said you got noise from using an inverter. It may be easier to get that noise out of the system than go with DC power. Was it a cheap inverter? Was it grounded properly? Did you run the power wires near the audio wires? Those are some of the problems that cause noise in the system.

10. It seems your are exactly right, if I want to use this monitor I will have to use an inverter, after replacing the fuse I blew and crossing my fingers that I didn't destroy the board. The inverter I have now is a Xantrex 1000w. It was being powered by a 4 gauge power wire and 4 gauge ground. I believe the ground is good. Anyhow, today I was lucky enough to be given the gift of about 25' of welding wire (I work in a steel fab plant). Pretty sure it's 0 gauge, but it's old and greasy and can't find the size written on the insulation. I am going to test the inverter with two short lengths directly to the battery and see if the buzzing stops. If it does that means my goal is attainable. If it still buzzes on a 12" power and ground, I will have to go to plan B, not sure what that is yet. I know plan B is going to involve \$\$\$. :-)

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