Pentax LX Repair

• Degraded rubber dampers: The Pentax LX included several rubber dampers in the mechanisms of the camera to reduce noise and vibration. Unfortunately, the material has not aged well, softening and leaking sticky oils into neighboring mechanisms. There are two dampers in particular that can cause problems with operation. The mirror rest damper is visible on the left side of the mirror box when the mirror is flipped up. As the rubber ages it softens causing the mirror angle to lower. Consequently, the viewfinder will no longer be able to focus on objects at infinity. The mirror rest can also get sticky, causing the mirror to hesitate before flipping up. The second damper is located on the side of the mirror box and requires significant disassembly to access. Due to its location, it can greatly impact the movement of the mirror, causing slowness throughout the entire length of travel. Eventually, the contamination will completely seize the mirror and the camera will be inoperable. Replacement dampers can be 3D printed using the model file on this page. Choose a soft thermoplastic such as TPU or TPE to get a rubber-like elasticity.
  • Pentax LX Mirror Box Mechanism Disassembly
• Oxidized variable resistors: The LX uses three variable resistors to communicate exposure settings to the electronics of the camera. The resistors consist of a PCB with a resistive strip along with feeler contacts that travel along the strip. It's common for the shutter speed resistor and the ISO resistor to develop oxidation on the contacting surfaces, resulting in intermittent electronic failures. The most common failure is the mirror locking in the up position with the opening shutter curtain (with the checkerboard pattern) still visible through the lens mount. Moving the shutter speed indicator to one of the mechanical speeds should return the camera to its normal unwound state. Cleaning the resistors may return functionality, otherwise, replacement parts are required.
  • Pentax LX Shutter Speed Resistor Cleaning
  • Pentax LX ISO Resistor Cleaning
• Various electrical issues:

If you are already performing significant disassembly of the camera for a repair, consider doing a more complete overhaul of the camera to reduce the chance of future issues. The following service will address the most common failure points of the Pentax LX.

• Mirror box mechanism: Remove old degraded rubber bumpers and clean all affected components.
• Viewfinder: Clean and replace old foam light/dust seals.
• Light seals: Remove and replace old foam light/dust seals.

• Open cell foam, self-adhesive, 1.5 mm thick: For light seals and mirror bumpers
• Isopropyl alcohol: General cleaning
• Cotton buds: General cleaning
• Contact cement: Adhesive for attaching leatherette
• Molybdenum grease: A thick grease for lubricating and reducing wear at mechanical latching points
• NyOil: A low viscosity oil used to lubricate the high speed mechanisms in the shutter
• Contact cleaner: A spray cleaner for removing oxidation from electrical contacts. Deoxit D5 is an example.

See the Pentax LX Troubleshooting page.