[PollitowuzHere]

After several weeks with a meter that would work intermittently, the MX's meter finally died today. I checked the batteries, the on/off switch, the film advance stand off, basically everything, and yet the meter doesn't work when the shutter is half-pressed. The camera had a CLA to fix a broken part almost 6 months ago by Eric, so I doubt that it's the replacement part. Maybe the loose baseplate?

[asaru]

Um, what do you mean by on-off switch? On the MX, the on-off switch, so to speak, is the film rewind lever, but even if it is not half-out a normal meter works while the shutter is half-depressed.

Anyway, it could be as simple as the wire to the LEDs breaking or being jarred loose.

There's a service manual for the MX available at Pentax Manuals. It has diagrams of where the various components of the meter circuits go, so you can play at a (very superficially "potential") diagnosis even without necessarily disassembling the camera, just by correlating things to the external appearance of your camera...

[PollitowuzHere]

By on-off switch I meant the ring surrounding the shutter release, shutter lock I think is a more accurate term for it.
Oddly, after slapping the camera softly, the meter started working again.

[GerryL]

By on-off switch I meant the ring surrounding the shutter release, shutter lock I think is a more accurate term for it.
Oddly, after slapping the camera softly, the meter started working again.

Maybe it woke up from being slapped?

[asaru]

By on-off switch I meant the ring surrounding the shutter release, shutter lock I think is a more accurate term for it.
Oddly, after slapping the camera softly, the meter started working again.

Without pretending to any knowledge I don't have, the words "loose contact" come to mind.

[Nesster]

That switch is important to use: I didn't lock my shutter, and something pressed on the button... result: dead batteries.