An ugly fix for on ODIN OEC12C887A RTC

The Odin OEC12C887A chip contains a battery backed real time clock and a small amount of battery backed RAM. The battery and the crystal needed for this are part of the chip. Many old motherboards use these chips, and have them soldered onto the board. Of course, batteries don't last forever, and when they fail, motherboards lose the time, date and settings. Unfortunately it seems settings cannot be retained even while the PC is on. After applying settings, the BIOS reboots and then reports they're invalid. Some motherboards can function this way, with problems related to few settings, like floppy drive type. Others may not allow you to boot.

Then the proper fix is to unsolder the chip, solder a socket, and put a new chip into the socket. Though it's also possible to drill into the chip and connect a new 3V lithium non-rechargeable battery, such as a CR2302. I don't have a Dremel or equivalent, so I used a soldering iron. The result is ugly but it works. Here is a photo of the chip with exposed connections:

You can see 5 metal pieces among the melted plastic. Going clockwise you see a pin from the chip, a tiny bit of metal which it was pried away from (which connects to the bottom of the battery), the top of the battery, a bit of metal connecting to the top of the battery, and another pin from from the chip which was pried away from that.

To understand this better, imagine a normal dual in-line package (DIP) chip. The pins come out the side and bend downwards, in order to go through holes in the circuit board and connect to the rest of the circuit. In this case, some of the pins instead bend upwards, and connect to the battery and crystal. If you look underneath the board you'll see that some pins are missing, and some or all of those are bent upwards. Probably these devices start off as a typical DIP package, which is then encased in a second layer of plastic after those components are added.

The pinout can be found at https://www.betaarchive.com/forum/viewtopic.php?t=22000, in particular in this image. Pin 16 is negative, and pin 20 is positive. Pin 16 has continuity with motherboard ground. Pin 20 has continuity with the larger surface of the coin cell, which is generally positive. Probably the crystal is connected to pins 2 and 3.

It doesn't smell too bad, and controlling the temperature so it's mostly melting and not burning plastic helps. I'm not going to recommend it because plastic fumes might be unhealthy, and I certainly wouldn't want to do this on a regular basis. But the repair was a success. The PCI slot is fine too, with only very minor cosmetic damage to the outer surface.