Pentax Spotmatic Troubleshooting

The needle in the viewfinder doesn't respond when the meter switch is activated.

Install a new battery in the camera. The Pentax Spotmatic was designed to be used with 1.35 V Mallory PX-400 batteries. The best modern replacement is a 1.55 V 387s silver oxide battery. A 394 battery can also be used but the plastic carrier from the old battery needs to be transferred to the new battery. The difference in battery voltage will not affect the accuracy of the light meter.

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. Isopropyl alcohol or a contact cleaner can be used to clean oxidation.

Corrosion can also occur inside the camera. Start by removing the bottom cover and checking the contact between the battery compartment and the internal wiring.

Next remove the top cover and inspect the wiring at the light meter circuit. When the meter switch is on, you should be able to measure battery voltage at the black wire.

If the battery compartment is working but voltage is not getting to the light meter circuit, the problem may be with the light meter switch. See the guide on cleaning the meter switch to resolve issue in that mechanism.

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

When the shutter completes the exposure the closing curtain trips a latch, which releases the mirror and lets it return to the viewing position. If the mirror return latch is dirty, it may not be releasing properly. Disassemble and clean the mirror return latch.

It's also possible that the closing curtain is not traveling fast enough or with enough force to trip the mirror return latch. Getting the curtain back to a proper operating speed requires a more thorough shutter service.

If the mirror flips up but doesn't trigger the shutter, it could be blocked by the meter switch. There is a small lever on on the upper right wall of the mirror box, near the focusing screen. When the mirror flips up, it pushes that lever, which turns off the meter switch. If the meter switch is dirty and not moving smoothly, it can prevent the mirror from completing its full travel and triggering the start of the shutter. Disassemble and clean the meter switch (most of the meter switch mechanism can be accessed by simply removing the front lens board).

The shutter won't fire and the advance lever is stuck. It won't do anything.

The most common cause is that the mirror charge lever has slipped off its latch, returning it to the released state. But this causes the shutter and the mirror to be out of sync (one is charged, the other is released) and the camera cannot resync itself. Remove the bottom plate of the camera and inspect this area. If the charge lever is at the bottom of the slot, near the gear, it has slipped off the latch. Push it up until the return latch catches and holds the lever. Test the camera.

The mirror charge lever is the most common cause, but there are many other points in the release sequence where a malfunction could lead to a jammed camera. The best way to hunt down unspecified problems is to remove the mirror box from the camera and inspect the mechanisms individually. See the guides on mirror box and shutter disassembly for details.