Praktica BX20 repair & common faults
Excellent coverageThe Praktica BX20 is an East German Pentacon-built SLR from the mid-1980s, part of the Praktica B-mount family that replaced the older M42 screw-thread cameras. It runs aperture-priority auto exposure through an electronically timed shutter, with a mechanical 1/125 and B kept in reserve for when the battery gives out, so most faults trace back to either that electronics chain or age in the mirror box and door seals.
Aperture-priority auto exposure with mechanical 1/125 and B backup · electronically timed vertical metal-blade shutter · centre-weighted CdS metering · 2 × LR44 (1.5 V) · Praktica B bayonet mount
Common Praktica BX20 faults
Praktica BX20 won't fire at all
A completely dead release usually means power isn't reaching the shutter's electronics rather than a jammed mechanism, since most speeds on this body are electronically timed. A fresh, clean set of button cells is the one thing worth trying first. If the battery check still shows nothing with new cells fitted, the fault has moved into the switch contacts or wiring and needs the camera opened to trace.
Praktica BX20 meter needle or LEDs dead or erratic
A meter that won't move, jumps about, or gives inconsistent readings for the same scene points to the metering circuit rather than the shutter, and is common on cameras of this age as contacts oxidise and cells degrade. Checking for corrosion and swapping in fresh batteries is worth doing first. If it stays dim or unresponsive with good power, the CdS cell itself has likely failed.
Praktica BX20 slow shutter speeds sticking or dragging
Fast speeds firing cleanly while anything below around 1/30 hangs or drags is a classic sign of old lubricant gumming up the shutter's timing mechanism, sometimes compounded by drift in the electronic timing itself. It isn't something a battery change will cure. The mechanical 1/125 and B speeds bypass this and stay usable in the meantime, everything else needs the shutter attended to.
Praktica BX20 mirror slow to return or bouncing in the viewfinder
A finder that blacks out and takes a beat to come back, or a mirror that visibly bounces before settling, points to the foam damper in the mirror box perishing with age, which is extremely common on cameras this old. It won't fix itself and left long enough can cause the mirror to hang up or clip the shutter on its travel. There's nothing to check without opening the body.
Praktica BX20 light leaks or fogged edges on film
Fogging along one or two edges, or fogging that worsens the longer a film sits loaded, almost always comes from the perished foam seals around the film door rather than the shutter. That foam turns sticky then crumbly and stops sealing properly with age. Running a finger along the door channel for tackiness is the one useful check, beyond that it's a straightforward foam job.
Stuck on your Praktica BX20?
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Try it now ›Scatto is a reference tool for people who service film cameras. It explains mechanisms and quotes service data, but it cannot see your camera at the bench, so verify anything load-bearing before you act on it.