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Pentax LX ISO Resistor Cleaning

Pentax LX ISO Resistor Cleaning

Sam Gustafson

Sam Gustafson en een andere bijdrager

Voor het laatst geüpdatet op February 28, 2025

30 minuten
Eenvoudig
Door de gemeenschap gemaakte handleiding

The ISO resistor is a common point of failure in the Pentax LX. The component consists of a pair of feeler contacts sliding along a carbon filament. The resistance value created by this assembly communicates the ISO and exposure compensation settings to the camera. Over time the contacts can become oxidized and/or dirty resulting in erratic meter readings in the viewfinder. Cleaning the resistor can restore the camera to normal functionality.

Any disassembly of the LX body will compromise the weather sealing. New seals must be reapplied during final reassembly to restore weather proofing.

Wat je nodig hebt

Gereedschap

  1. Pentax LX ISO Resistor Cleaning, Remove rewind knob: stap 1, afbeelding 1 van 2 Pentax LX ISO Resistor Cleaning, Remove rewind knob: stap 1, afbeelding 2 van 2
    • Place a thin tool in the rewind fork and unscrew the topside knob.

    • Remove the washer under the rewind knob.

  2. Pentax LX ISO Resistor Cleaning, Remove exposure compensation dial: stap 2, afbeelding 1 van 3 Pentax LX ISO Resistor Cleaning, Remove exposure compensation dial: stap 2, afbeelding 2 van 3 Pentax LX ISO Resistor Cleaning, Remove exposure compensation dial: stap 2, afbeelding 3 van 3
    • Remove three #000 5.5 mm screws.

    • Remove exposure compensation dial assembly.

    • Remove washer.

    • Remove rubber seal.

  3. Pentax LX ISO Resistor Cleaning, Remove rewind side top cover: stap 3, afbeelding 1 van 2 Pentax LX ISO Resistor Cleaning, Remove rewind side top cover: stap 3, afbeelding 2 van 2
    • Remove one #00 X mm screw.

    • Remove one #00 2.5 mm screw.

  4. Pentax LX ISO Resistor Cleaning, Clean ISO resistor: stap 4, afbeelding 1 van 2 Pentax LX ISO Resistor Cleaning, Clean ISO resistor: stap 4, afbeelding 2 van 2
    • The resistor assembly is crimped or pressed together and further disassembly is not possible.

    • Use a cotton bud and isopropyl alcohol to clean the surface of the resistive element.

    • Spray a plastic safe contact cleaner in the area of the feeler contacts.

    • Rotate the dial back and forth several times.

    • Check the resistance between the purple wire and ground. It should range from 7.5 kΩ to 200 kΩ with no dead spots.

  5. Pentax LX ISO Resistor Cleaning, Replace ISO resistor: stap 5, afbeelding 1 van 1
    • If the resistor still doesn't function properly after cleaning, remove it a replace it with a new part.

    • Unsolder one purple wire.

    • Unsolder one green wire.

    • Unsolder two brown wires.

    • Remove three #00 screws.

Conclusie

To reassemble your device, follow these instructions in reverse order.

Sam Gustafson

Lid sinds: 09/01/22

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