You can find a lot of strange things inside IC packages. For example, the Dallas DS12885 and DS12887 real time clock “chips” were available in a large package with an internal battery. The problem, of course, is that batteries die. [New Old Computer Show] wanted to restore a machine that used one of these devices and was able to repair the device. You can see two videos below. In the first video, he replaces both the battery and adds an external oscillator which would be necessary for the DS12885. However, he actually had the DS12887, which has an internal oscillator, something the second video explains.
The repair used a PCB he ordered from Tindie. However, the board is only part of the problem. You also need to disconnect the dead battery which requires a Dremel and a steady hand.