I went on a 286 repair binge. Specifically, the machine would work fine except the onboard speaker header didn't work. No beeps, not from the POST, nor from Duke Nukem.
Originally, I tried tracing the connections all over the board to see if there were any broken traces. There were some rough traces but I eventually abandoned that endeavor and looked elsewhere. I learned that tapping the OUT 2 from the chipset works but not really; you'll get sound but after the first sound effect plays it'll leave a constant hum. Well, that's no good. So I traced further and found the AND gate that properly controls the speaker output. Tapped that and sound worked! And then the machine would lock every time. Turns out you need an open-collector gate to properly handle the signal. Maybe that's why the traces on the board go cold on the AND gate's output point, next to a ground pin and another pin that... ends at another dead end with three solder points? And one of those solder points connects to P17 on the P8242 chip on the board? And the other pin connects to a series of traces that dead-end at a point where a capacitor is marked but not soldered, which if bridged or replaced would complete a circuit to the speaker output pin, even though that same speaker output pin also traces back to where I saw a series of damaged traces..
Oh hell. I got the thing to output some speaker audio well enough and it even routes through the Blasterboard fine. I tried making a filter capacitor circuit but everything went silent with the capacitor in place. I'll take any recommendations at this point. I feel like I've learned something about hardware and troubleshooting that I never meant to. It feels good but it sure was a pain in the ass.
I spend my days fighting with clunky software so I can afford to spend my evenings fighting with clunky hardware.
