LC III ADB port not working

[VoraciousGorak]

So this is basically a copy of the issue posed here, but instead of resurrecting a 2-year-old thread I figured I'd post a new one. I just recapped my LC III, and though it was my first recap ever and might be a little sloppy, the machine has gone from "nothing on screen, screaming speaker, no hard drive power" to "boots to System 7, but ADB port doesn't work."

I've checked the solder jobs as best I know how, resoldered a couple of them to be sure, checked the ADB voltage (4.87V on the 5V pin), and checked multiple ADB keyboards and mice that I know to work on my 637CD. So far, nothing. I've cleaned the board a few times with alcohol, contact cleaner, and one run through the dishwasher. What should I check next? My tools are very basic, just a multimeter and a soldering iron currently.

 

[AwkwardPotato]

Pictures of the top and bottom of the board might help in spotting bad traces. If you've redone the solder joints on the ADB connector, take a closer look at IC U7 (between the FPU socket and ADB port). Try following the traces back from the ADB port through until you reach U7 and make sure none of them are broken. Clean the area around U7 and its pins very well. If that fails, reflow all of the pins on U7 by drag soldering (lots of tutorials on YouTube, it's pretty easy to get the hang of).

U7 is also referred to as the EGRET chip and is involved with ADB, among other things. It behaves erratically when exposed even to trace amounts of cap goo and can cause all sorts of problems.

 

[VoraciousGorak]

Ooh, good to know, thanks! My workspace is occupied by another project currently, I'll try the reflow and check conductivity along the traces and if that doesn't work I'll try to get some high-res pics.