My trusty Pentax MX went south on vacation--I set the timer to take a picture of myself and when it got to the end of the timer cycle, the shutter didn't release. The indicator still shows orange, and the winder won't wind, but when I press the shutter release button nothing happens.
The timer still 'clicks' at the end of it's cycle and draws the shutter release down about 1/2 way, but the shutter won't move.
I don't have an immediate solution for you - but it is easy to reach the MX self timer mechanism: peel back the leatherette at both sides of the lens mount and remove 4 screws and the ST lever to pull the front panel off (i THINK you can do this without removing the top cover but i'm not positive). Remove the mirror trip lever from the front of the shutter release shaft, and then you can remove the self timer from the camera.
There's a good chance that you won't have to actually disassemble it this far to find the problem.
