Can I use a Step-Down Transformer to lower the output voltage of an AC adapter?

Here is the deal... I have an IBM LCD monitor that I got on the cheap from Ebay, the issue was that it didn't have a base or a power supply. Big deal, I thought because the plan was to wall-mount it and I had 6-7 old ac adapters lying around that would have roughly the same voltage and amperage. So,... show more Here is the deal...

I have an IBM LCD monitor that I got on the cheap from Ebay, the issue was that it didn't have a base or a power supply.

Big deal, I thought because the plan was to wall-mount it and I had 6-7 old ac adapters lying around that would have roughly the same voltage and amperage.

So, now that I got it in the mail, I find that it requires a 12v 3.0 amp adapter. Unfortunately, all the adapters I have that provide enough amperage are all 19V or higher.

Back to the question, couldn't I just add a transformer inline with the output cable to step down the voltage to a level that will not fry the monitor?

Where could I find a step-down transformer that small?
Update: The adapters I am looking to use are all old notebook adapters. I imagine these are too well regulated to work considering what you are all telling me. The main point of this was to figure out a way to do it and avoid having to buy the adapter outright. There is a good level of satisfaction knowing that you... show more The adapters I am looking to use are all old notebook adapters. I imagine these are too well regulated to work considering what you are all telling me.

The main point of this was to figure out a way to do it and avoid having to buy the adapter outright. There is a good level of satisfaction knowing that you were able to avoid spending money by doing things yourself.
Update 2: I found a 15v 4A adapter, but again it is a notebook adapter. Looks like I will have to suck it up and buy a new one, unless anyone has any other ideas...
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