I have just been following some traces around inside an old digital multimeter (AVO DA116). I was poking around at the LCD driver chips (MC14543CP) when I noticed that the power supply was short circuit. (There was about 1 ohm between the VDD and VSS pins).
The main power switch is a rotary switch with many contacts arranged on the PCB. The power switch is also a mode switch. It has four positions, three are on (three different modes) and one is off.
After more poking around and referring to the schematic, I found that the power switch will short circuit the power supply for this chip when it is in the off position.
When I turn the power switch to any of the three on positions, the short circuit disappears (yes I am testing without batteries installed). The schematic agrees that this switch is directly short circuiting this supply when it is in the off position.
I was wondering why this might be and the only theory I have is that it is useful for lining up the switch mechanism with the knob. The knob is part of the case and is the section with the endstops that limit the switch rotation. The switch contact assembly on the PCB can be inserted in several different orientations and so perhaps in the factory, the switch assembly was turned until the power supply was short and then the knob was turned to the off position before the two were joined to ensure the correct orientation was selected.
Is there another possibility? Is this some design practice I don't know about? Is it a bad idea or a good idea?
-- edit --
Here is the schematic, the red arrows point to the contacts on the switch, I highlighted the traces that go to the power supply in blue. The power supply is on a different board and connects via the connector at the bottom of the schematic (SK4, 15 pin header) the image is a little blurry but I added in the voltages that were annotated near the bottom.
Bigger picture here: http://i.stack.imgur.com/at75d.jpg
High res scan here: http://bitofahack.com/images/other/AVO_Schematic.jpg