A few days ago, I fixed my brothers Thinkpad, after breaking it while trying to fix it.
When he gave it to me, it definitely acted weird, as it was showing me a black screen only, while working fine with an external monitor.
I tried to diagnose whether the backlight was faulty, and interestingly, it didn't seem to be. When I shone a light on it, I couldn't see anthing. Strangely enough, the display was seemingly turning on and off while booting or going to standby mode, but never showed anything. An hour of research on the interwebz didn't turn out to be a good use of my time. My brother told me, that when the screen went dark, it had been flickering before. So I wanted to make sure it wasn't simply a connection issue.
When I took the panel out of its frame, I immediately noticed that the 40 pin LVDS-connector wasn't fully inserted. I fixed that problem, reinserted the power plug, pressed the power button and, to my delight, was greeted with a Lenovo Bios Screen.
But as turned out, I was celebrating victory too early, because after I screwed in two screws, I thought to myself, well, before continuing to assemble the frame, I should make sure it still works. So I reinserted the power plug, pressed the button and was pretty disappointed to only see a black screen. And now, this must have been the point where things went south. While unscrewing the panel to re-check the connection, I left the power plugged in. As I learned later, this is something you really, really shouldn't do. Even if the laptop is turned off, you still have your 19 volts going to the display. So after wiggling the LVDS connector back into position, I could see that the backlight of the LCD wasn't working anymore.
I absolutely knew that I had broken something, so I spent the rest of the evening actually learning a bit about that Thinkpad.
The next day, according to some youtube video, I measured the voltage of the 4 19 volt pins on the connector. My multimeter showed only 15 volts. I didn't know what this was supposed to mean, as I either expected about 19v or something way off. But 15v it was. So I thought of giving a check on the backlight fuse a shot.
Following some reddit post and an absolutely unrelated youtube video, I disassembled the Thinkpad to get to the lower side of the main board. As easy as replacing the components of a Thinkpad usually is, as annoying was getting to that part without having done it before. With laptops, I always have that feeling that disassembling them for the first time takes about 10 times as long as it does for the second time.
Anyways, after removing basically everything and a few more screws (this thing really is built like a tank), I could remove the back plate and lift up the black sticker on the back side of the LVDS connector on the main board.
With the thinkpad body upside down, but with the LVDS connector away from you(and on the other side of the board), you will find to the right of it a fuse. On the Thinkpad T430 it's labeled "F7". As fas as I know, this differs for other Main Boards.
I measured that fuse with a multimeter, which showed that it didn't have continuity. So I was having a bit of hope that I might be able to fix it. The fuse only had the letter "P" on it. I don't know much about SMD fuses, but it appeared to have a 3A rating. It was a 0402 part though, which I never used before.
So I didn't have a replacement part and buying one would have been relatively expensive and have taken a long time, but I didn't want to just short it. So I settled for some middle ground and took a 0603 fuse from an early 2000s PC mainboard.
It had no writing on it, so I simply ran 3 Amps through it (I don't have a stronger power supply), which didn't blow the fuse, so I deemed it fine for my purposes. It's better than a solder blob, at least. Cramming a 0603 part there where a 0402 part should be was as horrible as it sounds, but the end result turned out fine. For desoldering the broken part, I used a 30€ hot air station and some cheap chinese flux. Soldering in the new part with the default tip for the TS-100 (which afaik isn't suited well for this task) also worked.
After measuring for continuity again, I concluded that I had to try to attach the screen and luckily, it worked. So I reassembled the laptop and gave it back to my brother (actually as a late birthday present) and was quite happy with the result.
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