Pentax ZX-5n Repair

The Pentax ZX-5n is a notable camera primarily due to its unique control scheme. Instead of using a command dial combined with function buttons, as was the standard at the time, it uses a dedicated shutter speed dial similar to older manual focus SLRs. It also has dedicated controls for metering modes, drive modes and exposure compensation. Combining all of these features into a small and lightweight package puts the ZX-5n in a unique position among other AF film SLRs.

The ZX-5n was the successor to the ZX-5. While being essentially the same camera (they share many internal components) it did get a few notable upgrades like exposure lock, depth of field preview, bracketing and the ability to select a single AF point. The MZ-5 and MZ-5n were the model names used in international markets. They were followed by the MZ-3, which added a higher 1/4000 shutter speed at the top end.

Unfortunately, the ZX and MZ line of cameras suffered from significant design flaws, which resulted in many broken cameras. Here is a list of failures listed roughly from most to least common.

1. Mirror Motor Gear: The motor that drives the reflex mirror has a small plastic pinion gear press fit onto the shaft. Over time the plastic gear will crack and lose engagement with the shaft. When this happens, the camera is no longer able to drive the mirror position or charge the shutter. Pressing the shutter button results in a low whine as the motor spins but nothing else. Eventually, Pentax began building some cameras with brass pinion gears but it's hard to tell which cameras received the upgrade without disassembly.
2. Flash Pivot: The pop-up flash has two plastic pivot pins. One of the pivot pins is forked at the end to accommodate a spring. Eventually, the fork splits and the spring can no longer "pop-up" the flash.
3. Mirror Drive Lever: The lever located on the side of the mirror box that directly drives the mirror is also plastic. If this breaks, the mirror will be stuck in the up position but the shutter will still fire.
4. Shutter Button: The contacts within the shutter button can become oxidized making certain functions like autofocus and shutter release intermittent and unreliable. If the camera operates normally with an alternate trigger (like the Remote Cable Switch F) then the shutter button is likely the source of the problem. The switch can be de-soldered and cleaned rather than requiring a replacement.
5. Overlapping Frames: The film advance motor also uses a press fit plastic pinion gear. If the gear starts to slip, the film will not be fully advanced to the next frame. When the next frame is exposed, it will overlap with the previous frame.

See the Pentax ZX-5n Troubleshooting page.

• Pentax MZ-5 Service Manual
• Pentax ZX-5n Operating Manual