While trying to install MS-DOS 6.22 and Windows for Workgroups 3.11, the Mega PC suddenly appeared to develop a power short. I tried another power supply, switched it on and was rewarded with plumes of smoke rising from the machine.

After pulling everything apart, I found that a tantalum capacitor on the Seagate 107 MB hard drive had failed dramatically. The failed capacitor was the obvious source of the smoke and short-like behaviour, although I still need to inspect the surrounding circuit before assuming nothing else was damaged.

The original part is 15 uF, 25 V in a case-size D package. I’ve ordered a replacement. Capacitance, polarity and physical fit obviously matter. A replacement voltage rating can be equal to or higher than the original where the package and capacitor technology remain appropriate.

In the meantime I installed a 517 MB hard drive and got MS-DOS 6.22 and Windows for Workgroups 3.11 running again. The video above includes some Windows MIDI playback using the Mega PC’s AdLib-compatible FM hardware.

I also managed to get the network card talking far enough to ping RetroJunkie.net over Ethernet.

That can become another project for another day. ;)

Sources