Unstable PC hardware – sudden hangups

One day my keymaster server stopped responding. I connected a monitor to it and tried to poke it over the console, but to no avail. Out of other options I rebooted it. Only to discover that during boot – just before login prompt appeared it hanged. Tried ctrl+c, remote login, even ping – no response. I powered it down, checked the temperature of the CPU radiator and other things, but it was OK. I pushed in all the plugs and cards, and booted it one more time. It hanged again, but while starting some other service than the last time. My friend who was around at the time asked me what’s wrong, and trying to come up with some smart answer, I said, “Oh, it’s probably the capacitors, either in the power supply, or by the CPU. By drying they fail to support the CPU with a stable voltage, and then it hangs.”. My friend had a closer look at the motherboard, which was very conveniently wide open at that time, and asked: “Like these one here?”. Sure enough, the big caps right by the CPU vented and had some stale electrolyte around the top.

At first I thought that it’s day has come. It’s a P4 motherboard that I bought at the De Anza flea market for $30. I liked its small factor (Mini-ITX). But over the years I put so much effort into making it work, that I felt that it would not be right to throw it out without even trying to revive it. I moved the disks and services to my other server (taurus), and had a look if I could found some fresh capacitors nearby, as I knew this was pretty common cause of a motherboard failure. I found some on a local auctioning site, and before too long got to repairing. First I de-soldered the deceased ones:

Vented Caps

I also located one more suspiciously looking cap apart from the row by the CPU and removed it as well. De-soldering required a lot of heat, since it’s a multilayer board, with a lot of copper nearby. Here is a side-by-side comparison of the old-versus-new caps:

Old and new capacitors

Old and new capacitors' tops

I put the new ones into place:Caps replaced

I booted the old fella, and to my content, steady he goes.

Later on I even found a Wikipedia site about related failures, called Capacitor plague.