Buying defective monitors when you don't know how to repair is a risky investment unless you got them for next to nothing. I just repaired one of these but it 's problem was different.

The "B" model is must more information available on repair.

You could swap parts to see if you could make one good monitor. Do you have electronics knowledge? There are some componets inside which could cause quite a shock. 

I have a E173FPC LCD and it stopped working after several years, with the following symptoms: 1) black screen 2) On button stays green when on 3) Monitor test does not show the Red/Green/Blue bars floating on the screen. Check out the Dell monitor page before going further with this, to be sure you have eliminated all possibilities.

http://support.dell.com/support/topics/global.aspx/support/dsn/document?c=us&l=en&s=gen&docid=290543

Once you have concluded that the issue is as I have described, you need to disassemble the screen. There's a description on YouTube, part 1 and 2:

http://www.youtube.com/watch?v=5WLzdjYnbDE

http://www.youtube.com/watch?v=ziyE0dq6OrA

The model is slightly different, but the process is the same.

I used a large flat-head screwdriver to pry off the front. I don't own a pry tool.

Inspect the backlight inverter / power board (the large one) for blown capacitors. There are descriptions on how to replace them on YouTube, if you find one or some. You need a soldering iron. I thought I had found a couple and replaced them, but that turned out not to be the problem. The capacitors were OK. I wasted time and money, but it was a learning experience.

It turns out some other part on the board was bad, so I bought one online from LCD Repair. It may be easier to just buy a new one and be done with it.

http://www.lcdrepair.us/

Cost was $29.99, plus $10 shipping. It arrived as promised within a week. I removed the old board and popped in the new one. That fixed my problem once and for all.