Achilles

I've been working on my collection of LCD displays. I had one that wasn't working properly and one that didn't work at all. I'm working on the wimpy one, but the dead one is back to life. I'm calling it Achilles for the reason that it was felled by one stupid little capacitor smaller than a pencil eraser.

Using the multimeter my grandpa Floyd gave me in 1994, I checked out the culprit capacitors as noted by this link and found C507 was clocking in at .5 microfarads in-circuit. It took me about half an hour to find anything with a replacement of the proper rating before I cannibalized one from the spare guts of a wireless Logitech controller. Soldering it with my ten year old Tenma station and the original ten year old tip was difficult, but it worked.

Testing the suspect capacitor out of circuit revealed the same .5 microfarad reading. You are the weakest link, goodbye.

Upon finishing installation of the cap and reassembly of the electronics, I plugged the display in to see a quick flash of the status LEDs and then a blank display with an amber power LED. Turning the display off then on yielded the Dell test pattern. It was working as far as the insides, but would it take a signal?

After gathering the hardware (which I had knocked off the top of a computer tower and scattered all over my messy floor) and putting everything back together, it was time to see if the display would... display... anything. With VGA output from the Alienware hot with an SXGA signal, I plugged in and powered up to see the desktop wallpaper and a rather dim display. Whoa. Low brightness setting? Nope, it's maxed in software.

As is the case with many displays that see duty in a college computer lab, this one had seen heavy use. And, being made in 2001, it had seen more than five years of it before I got hold of it for a dollar in broken form. I'm unable to access the factory menu to see an hour counter like the ones on my 1800FP and 2001FP, but I don't need the details to know this beast needs a re-lamping. I'll wait until I find a broken LCD I can't resurrect or get a few tubes for cheap before I do that piece of surgery.

Until then, I'll put this thing to use, yellowish display and all.

For the record, the panel in this is an LTM170E4 model which is an 8-bit per channel part. No dithering is used and all colors are directly addressed. Unlike my HP F1703, this one has a DVI port, too.

The F1703 is a good story to tell:

In 2004, my wife's grandma told me her LCD panel had just died. It would come on for a short moment and then the backlight would shut off, leaving a very dark image. She let me take it to see what I could do with it and I couldn't find anything obvious. She elected to order a new panel, which is still serving her well.

I figured the problem could be solved by purchasing a display of the same model with a cracked display panel off of ebay and transferring parts between the two. I ended up dropping about $90 on a panel with the middle third of the viewing space blacked out across the LCD. I figured I'd put the good LCD in the good case and call it a day, trashing the rest.

Wrong. I took the ebay display apart to find the components were completely different. Where grandma's display had a Chunghwa LCD, the ebay one had a Samsung. The LVDS connector was the same, but the backlight connectors were completely different, the Samsung having four where the Chunghwa had two. It was while putting the ebay panel back together that I noticed the black bar would come back intermittently. I figured I'd have a look inside deeper to see if I could find anything.

It was one of the control ICs driving the horizontal lines. There were three and the middle one was tweaked out of position, facing away from the others. Factory defect or not, I put the LCD module back together with the ribbon facing the correct way and fired the panel up. It worked. I gave it to Allison to replace her rather clunky Dell CRT, but after hooking it up, the bar was back so I gave it a whack and everything was fine. Has been ever since.

So the next LCD is a Gateway model that will run just fine for about half an hour and then go blank until power cycled. I'll post an update when I get to the bottom of that issue.