The cold cathode backlight driver for my Samsung SyncMaster 2494 monitor ate itself. As they run somewhere around 800v, it carbonized a good section of the board when it went.
The carbonized bit contained a bank of onboard resistors, which were unrecognizable. I *guessed* that they were ballast resistors. Hell, I guessed they were resistors...
I carved out the destroyed bit, experimentally determined the required values for the ballast resistors (330k), and built one out of stuff on-hand. The first version started to heat up, so I added the copper strips to dissipate the heat.
I'm not particularly proud of this, but after a generous application of nail polish, I'm now using it to write this article...
So far so good. I don't think it has ever been powered down since the repair, barring the occasional thunderstorm. So it seems that this did the trick.
The next post will be when it eventually eats itself.
It is a cold cathode back-light after all and has been powered on at least 8-12 hours a day since I bought it 10 years ago. So... see you in 2-4 years?
I really like this monitor actually. One can only hope.
To find the right value, I just randomly tried some in what I thought was the right 'range'. I got pretty lucky and had it on the third try.
At 440k the leads were arcing, and it shut down.
At 220k it dimly powered on, then shut down.
At 330k it powered on and worked. However, the SMD resistor bank I made for it got a bit warm. Warm enough to start to degrade my nail polish. The old resistors were smaller in size, but they could also use the board itself as a heat sink. Mine are naked.
So I took it back apart and soldered the SMD resistors onto some copper strips to act as a heat sink. They needed to be a fair bit apart to work at the required voltage, so getting it to fit in the space available with sufficient clearance to avoid arcing required raising it off the board.
That's about it.
I've already gotten 10 years of use from this monitor. It's 1080p, great contrast, and DVI (which I can run HDMI into) so it still checks all the boxes.
If I get another one or two years out of it this way I'll be happy. The cold cathode tubes will likely die next.
<EDIT>
3 days in, always on, no issues. Took it apart and looked at it. No change. The copper bits are doing a good job of being the heat sink I needed.
Now that's what I call field-expedient! Plenty to be proud of there, IMHO.