Pentax LX Troubleshooting

The LEDs in the viewfinder don't light up.

Install new batteries in the camera to ensure that low battery voltage is not the issue. Batteries should be inserted with the positive side facing the battery compartment cover.

Check the contacts in the battery compartment. Old leaky batteries are a common problem and the acid can corrode battery contacts. Vinegar can be used to clean the corrosion.

Corrosion can also occur inside the camera. Remove the top cover around the rewind knob and check the voltage at the red wire. It should be around 3.0 V. If it is lower, the connection to the battery compartment may be corroded.

The mirror flips up and down but it is slow. There is a delay in actuation after pushing the shutter button.

The Pentax LX has rubber dampers built into the mirror box mechanism that reduce vibration and noise during an exposure. Over time, the rubber degrades and a sticky oil contaminates the moving parts. The old dampers need to be removed and the mirror mechanism cleaned.

The rubber pad on the mirror rest degrades and becomes sticky over time. This can cause a delay in the release of the mirror but it should move quickly once free. The mirror rest needs to be removed and replaced. The mirror angle and viewfinder focus should be checked and calibrated.

The reflex mirror in the body of the camera is stuck in the up position blocking the viewfinder. The shutter won't fire and the advance lever is locked.

If the rubber dampers in the mirror box become significantly degraded, the mirror can get stuck and fail to return at all. The degraded rubber needs to be removed and the mirror mechanism cleaned.

The Pentax LX has a low battery warning mode to prevent the user from shooting in electronic modes with dead batteries. The mirror will flip up but the shutter will not fire and the mirror will not return. If the user removes the lens and looks inside the camera, the checkered pattern on the opening curtain should be visible. The warning mode is only active in 'Auto' mode and with the slower electronic shutter speeds. Turning the shutter speed dial to one of the mechanical speeds (X - 2000) will allow the camera to complete the exposure cycle and return it to its ready state.

If the camera operates normally in 'Auto' mode but triggers the warning mode when set to slower electronic shutter speeds, the variable resistor in the shutter speed dial is failing. Actuating the dial repeatedly can remove light oxidation and restore normal operation. Otherwise, the shutter dial assembly can be disassembled and cleaned or replaced.

If both 'Auto' mode and electronic speeds trigger the warning mode, the variable resistor in the ISO dial may be the issue. It can be removed and cleaned.

The warning mode can also trigger if the electromagnet is bad. The electromagnet is located underneath the bottom plate.

Viewfinder LEDs never turn off. Battery drains quickly.