Here’s a couple of pictures of the HP8112A (thanks Fred!) I recently repaired. Notice the battery and the yellow resistor pack next to it. Two pins on the resistor pack were shorted by battery corrosion/crud, holding the CPU ~RESET low intermittently.
Once the offending battery was removed and the icky crud cleaned up, it works like a champ. I will actually chop out that pack and replace it with a new one for peace of mind, and install a new battery away from the main board to hold settings. These old boat anchors are a pleasure to work on … notice how the CPU and control boards can be placed in “maintenance mode” for easy access to all test points.
