LED Illuminator for LOMO МБИ-3 i.e. MBI-3 

Vintage LOMO Biological Research Microscope LED Conversion

By Dushan Grujich, on October 6th. 2013

LOMO MBI-3 Biological Microscope

LOMO MBI-32 Microscope was produced during 1950's through 1960's Biological Research Microscope TL 160 mm, equipped with OI-14 aplanatic condenser 1.4 NA, with binocular attachment accompanied with a set of matched eyepieces, with a set of apochromatic objectives (shown in the table below) and a plan/concave mirror. An optional illuminator OI-19 can be used to provide Koehler illumination.

This stand has served as the basis for development of the Biolam 70 series microscopes two decades later.

Magn./NA TL/CS mm Working dist. mm Type Specifics
10/0.30 160/0.17 4.80 apochromatic  -
20/0.65 160/0.17 0.67 apochromatic  -
60/0.70-1.00 160/0.17 0.22 apochromatic  OI - IRIS 
90/1.30 160/0.17 0.12 apochromatic 


90/1.25 160/0.17 0.12 achromatic OI


I was asked by a local vet to do maintenance check, adjustments of the microscope and to do LED conversion of the microscope. One of the repairs needed was a typical failure of OI-14 condenser top lens element, which by now has for me become a routine operation. The LED conversion was done by applying the same principle I have used to convert the LOMO OI-321, except in this case there was need to fabricate the housing as well.



The image above shows the housing and collimating lens mounted on  top

I have managed to solve the problem of the new housing by taking a short piece of aluminium pipe 50 mm OD, with wall thickness of 2 mm. Out of aluminium sheet of 2 mm thickness I have cut cover to press fit the top of the housing. On its top side I have mounted the collimating lens which also serves as a holder for star diode, firmly holding it to the top cover, which also serves to provide additional heat sinking.  
The electronic module, KIS-3R33S, is mounted inside the enclosure soldered to a piece of breadboard, securely fastened to the bottom side of the top cover by use of brass spacers and two screws. Miniature potentiometer, incorporating the on/off switch, is mounted onto the outer side facing away from the observer while the 3.5 mm receptacle for the wall plug-in unit is mounted on the side. as visible on the photo above.


Instead of a collector lens I have used a 30 collimator lens which nicely and fully illuminates condenser, easily checked with phase contrast telescope 



Here we can see the illuminator under power firmly sitting in its position without wobbling or danger of disconnecting



Photo above shows the intensity control pot, 12 V DC receptacle and the arm which serves to securely mount illuminator instead of mirror



Another view of the illuminator and illuminator plug





1 - "A simple, low cost, conversion of incandescent-lamp illuminator to a power LED" by Dushan Grujich, published in November 2012 issue of Micscape magazine
2 - "Описание микроскопа исследовательского биологического МБИ-3", Website of Histology Department of Dnepropetrovsk Medical University 
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