i got a cute little IBM PS/2 Model 25! it has a built-in b&w monitor and MCGA graphics. but it needed a little work when i got it. 🧵

for teardown and inspection i had to remove the entire plastic case. the monitor inside is shielded entirely with metal held shut with security "flat" screws. no bad caps inside, no RIFA caps, nothing else looked damaged.

the floppy drive needed some work, however. the motor boards in these 720KB 3.5" drives have leaky SMD electrolytic caps. i had to clean the board and replace them.

the hard drive is this weird IBM 30MB model. the interface is a weird primitive form of IDE, but totally proprietary (apparently)

the computer boots with RAM errors. i decoded these the hard way by swapping SIMMS and chips around.

memory is strange in this system. there are two 256KB SIMMS. yes, kilobyte. that still doesn't add up to 640KB, so IBM added 128K using discrete memory chips! looks like one of these chips has gone bad.

this RAM chip has a little attitude! actually it was working just fine. the bad chip was a different one. i replaced it and the machine booted!

even though it has a hard drive, it's not the 286 version of the Model 25 (the only versions to come with a stock hard drive). in fact it has been upgraded with the famous NEC V30! an 8087 has also been installed. someone tricked out this machine.