I took a closer look with better lighting after removing some components. Y'all were right on about this being the issue. I found some of these "Chhsi" branded caps that were part of the known bad caps from that era. I am a bad solderer, but will try to get these replaced, and report back.

Horun wrote on 2022-05-10, 23:57: Did you clean the DIMM's edge connector ? Use paper towel with ISO alc....and do not be afraid to scrub hard ;p I did actually. Thanks for your suggestions though.

You could try cleaning the RAM sockets with some isopropyl or ketonatus alcohol and a soft tooth brush. Also check for any damaged pins in the RAM sockets, although I don't expect this to be the issue, since the system sometimes does work. Since it doesn't work on the first attempt, but it does …

I should note that even after being on for a long period of time, it doesn't boot reliably or anything. I wish I could tell if there was a bad cap somewhere, but visual inspection of the board is clean. I don't know where I'd start. I also noticed that it has a way higher chance of not booting when …

Just in case anyone has ever experienced this, I wanted to reach out and check here. I bought a 1999 IBM Personal Computer 300GL (Type 6275-90U). It's a Slot 1 Pentium III, Intel 440BX chipset, with a riser board for adding PCI and ISA cards and 3 PC100 DIMM memory sockets. About 50% of the time, …