I'm sure I could just replace that regulator with any 5v low dropout, low quiescent current regulator, but I'm curious what the original "701" is. Looking into what's driving the contrast line on the LCD next.
Removing the chip completely and applying 5V to the 5V rail, the board draws less than 10mA, and the display appears to initialize (starts with one line of dark squares, like an uninitialized character LCD usually does, goes blank, then comes back with 2 lines of dark squares), so I think the CPU is actually running, but the contrast on the display is way too dark, so I just get 2 lines of black squares. Feeding +5 directly to the 5V rail, the chip sinks 300mA and gets hot. Applying 9V from a bench supply, the chip gets smoking hot, and draws about 500mA. This is from a Nikon NE-20S digital theodolite. Maybe that helps identify a different regulator that was originally meant to go there. It looks like pin 7 originally connected to +5 as well as pin 8, but the pin 7 trace to +5 rail has been cut on the PCB, and pin 3 connected to pin 7 with the bodge wire.
The pinout is 1: +9V in (from 6 AA batteries in series) 2: GND 3: to pin 7 4: N/C 5: N/C 6: N/C 7: to pin 3 8: +5 out On the PCB, pin 3 connects to pin 4 with a trace under the chip, but pin 4 has been cut off the IC, so it's N/C now. Can anyone identify the "701 B43" chip in this picture? I'm pretty sure it's a 5v regulator, but I can't find any datasheet that would match the pinout, or any datasheet for a "701" that's a voltage regulator.
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