Pentax K100D Shutter Button
November 10, 2024
Just a short one today on some issues I was having when testing out a Pentax K100D digital SLR camera. All of the functions on the camera were working well except the shutter release was difficult to trigger. As is the case with most camera buttons it is a two stage activation with the first mid-press initiating a focus operation and then the shutter is triggered when the button is pressed to it's full actuation. On this particular camera the focus position seemed reliable, but the shutter trigger often required quite a hard press to activate.
Although this was not likely the be the culprit, one of the easiest things to do first is to ensure that the lens and the camera are making good contact, so removing the lens and ensuring the contacts on both it, and the lens mount are clean is worth a few seconds. I cleaned both sides with IPA and reattached the lens, but as expected there was no change in the shutter release.
Getting to the shutter release button does require some disassembly, and a service manual is helpful for this. I was able to find one for the K100D here which walked through the breakdown of the camera. The first step was to remove the bottom cover, then the side cover. Next it was important to safely discharge the flash unit, desolder the wires and then the top cover can be removed exposing the shutter button.
The shutter button is similar to a standard tactile switch but the top is a soft membrane rather than a full plunger assembly. Although you might be able to find a replacement switch I wasn't able to source one, so attempting to clean the existing one was the only way forward. Before starting I just made sure that the solder joints for the switch looked good as it would be a shame to pull apart the switch and risk damage when the issue could have been fixed from the outside.
Top of the switch removed
Membrane removed
Actuator spring removed
You can see in the pictures above how the dual-action actuation works, with the outer contacts pressing first to initiate a focus operation, then if the button is pressed further, the center will make contact to release the shutter.
Some IPA was used to very carefully clean the contacts within the switch and also the spring itself. You need to be very careful not to deform the spring which would lead to further issues.
Once everything was clean, the camera was reassembled, the firmware updated and it was tested out. The cleaned shutter release was much more reliable, now triggering with a normal press rather than Hulk-like mashing.
