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Leitz Trinocular Head FSA (512 738) Teardown

Written By: Reinier Blok (and one other contributor)

Published: June 4, 2026

Comments: 0
Favorites: 0
Views: 140

Leitz Trinocular Head FSA (512 738) Teardown

Written By: Reinier Blok (and one other contributor)

Published: June 4, 2026

Comments: 0
Favorites: 0
Views: 140

Teardown

Introduction

The Leitz Trinocular Head FSA catalogue number 512 738 is a trinocular Jentsch-type microscope head designed for microscopes with a 160mm mechanical tube length and eyepieces having an outer barrel diameter of 23.2mm. It contains a sliding beamsplitter assembly that directs light to the eyepieces and/or the trinocular port. This guide will provide a partial teardown to allow 'safe' access to the internal prism assembly.

What you need

This teardown is not a repair guide. To repair your Leitz Trinocular Head FSA (512 738), use our service manual.

1. Step 1 Leitz Trinocular Head FSA (512 738) Teardown
  Start by adjusting the interpupillary distance to the smallest value. The eyepiece shields should move forward and expose 2 flathead screws.
  
  Remove the eyepieces if present.
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2. Step 2
  Remove the M3x4.5 2.5 mm flat head screw and pull off the prism selector knob by pulling straight up.
  
  As with many of the fasteners on Leitz microscopes, it is made of brass. Take some care not to mangle or strip the fastener's head.
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3. Step 3
  Remove the 3 M3x5.5 Phillips 1 screws from the trinocular tube.
  
  When using an iFixit screwdriver set, using a J1 combined with a smaller bit driver allows for easier access, as the screws are located in an internal recess of the trinocular tube.
  
  Take care not to drop the screws, as the prism assembly is exposed underneath and can be damaged easily.
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4. Step 4
  Remove the 4 flat head screws.
  
  2x M3x8 5mm flat head.
  
  2x M3x6 5mm flat head.
  
  Take care not to drop the screws, as the prism assembly is exposed underneath and can be damaged easily.
  
  The front assembly is loose and can be lifted out of the head.
  
  Take care when lifting out the front assembly, as the prism assembly is exposed and can be damaged easily.
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5. Step 5
  Turn over the main head assembly.
  
  Remove the 4 M3x6 5 mm flat head screws.
  
  Removing the bottom cover undoes the factory-set optical alignment. However, the little side-to-side adjustments have very little to no perceivable effect on the generated image.
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6. Step 6
  Remove the 2 M3x8 Phillips 1 screws.
  
  When using an iFixit screwdriver set, using a J1 combined with a smaller bit driver allows for easier access.
  
  Removing the beamsplitter prism assembly undoes the factory-set optical alignment. However, the little side-to-side adjustments have very little to no perceivable effect on the generated image.
  
  The beamsplitter prism assembly has no stable position without having one prism side touching a surface. Placement on a clean Kimwipe or microfibre cloth is recommended.
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7. Step 7
  Loosen the M3x6 5mm flat head screw on the counter pinion assembly to loosen the tension on the timing belt.
  
  Remove the 2.5 mm grub screw and brass clamp to free the timing belt.
  
  The timing belt is a 4T5/245 (4 mm width, 5 mm T-type pitch, 245 mm circumference, 49 teeth).
  
  This beamsplitter prism assembly is fitted with a black aftermarket timing belt. The original timing belt is coloured yellow to light brown.
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