FABRICATION OF A REPLACEMENT SUBSTAGE LIGHT SOURCE FOR THE BH2/BHS MICROSCOPE

Figure 1. Olympus OEM illuminator housing, bulb, magnifier, diffuser, mounting tube and electrical connector. Not included in image are the transformer, electrical components and controller which are in the base of the microscope
The purpose of this posting is to satisfy the needs of amateur microscopists using Olympus model BH2/BHS with a failing illuminator. It is designed to be low cost, easy to fabricate, install.and maintain.
The BH2/BHS microscope has a substage incandescent light source that is standard with the instrument. The light source required a 120 V power source which is modified by a transformer and microcircuitry built into the base. There are two controllers for this lamp including a on/off power switch and a sliding potentiometer for intensity control.
PROBLEM STATEMENT:
The sliding potentiometer is no longer in production and all online inventory resources for a single replacement this part are out of stock. My Olympus BH2/BHS potentiometer was out of function. Attempts to clean it without disassembly of this substructure were unsuccessful. The other option was to replace the entire light source system with a new low voltage LED bulb.
The housing for the new light source was fabricated from easily available PVC plastic plumbing materials. Other materials listed below were easily purchased from online suppliers.
LIST OF PARTS OF THE ASSEMBLY:
1 !/2 X 2-inch PVC coupling
2″ PVC Pipe Vent Screen, 2.375″ OD, 1/2″ mesh
5/8-inch length of 1-inch PVC plastic pipe
Low voltage DC power cable, 5.5mm X 2.1 male connector ~ 10 inches of ~20 ga twin wire
Round Heat sink, 1 inch outside diameter, 2-inch length with internal space for placing screws
2 machine screws to fit the apertures in the heat sink (your choice)
2-inch disc of sheet ~1mm aluminum, (Secured from scrap packaging)
Aluminum tube 47mm OD X 78mm length
LED star with light frequency of your choice. (I used 460mm for the royal blue).
Thermo-adhesive for attaching LED star to the heatsink
Metallic duct tape to apply to the ID of the microscope substage rear illuminator port
Plastic 0.5mm clear plastic shim stock, (1cm X 15cm strips cut from scrap packaging)
TOOLS NEEDED:
Saw, to cut PVC and aluminum tubing (hand saw or power miter saw)
Scissors, to cut sheet aluminum and plastic
Soldering tool, for micro circuitry with rosin core solder
Thread tap, with sized drill bit for attaching the heat sink to the sheet aluminum mounting plate
Power drill motor
POWER SOURCE:
Variable Power supply available and purchased from the Empire of Dirt Workshop (empireofdirtworkshop.com) or contact Carl (carlh6902@gmail.com)
Disclaimer: I did not collaborate with Carl regarding the use of his power source. He makes his own design exclusively for Olympus BH2 microscopes. This illuminator is my design for BH2/BHS Olympus microscopes.
RESULT:
The new Olympus BH2/BHS microscope illuminator together with the power source provides perfect lighting for Olympus SPlan 5X, 20X, and 40X lenses. The heat generated from the illuminator assembly is minimal. Heat generated from the power source is also well dispersed from the heat sink of the power source.
I constructed three light sources using this method; white light, royal blue and royal blue with a fiberoptic cable for direct illumination. The royal blue light provides illumination to reacts with the green fluorescent protein in the marine organism subjects.
The internal electronics in the base of the microscope are not used but remain to maintain the mass of the instrument thus reducing photographic image blur from extraneous vibrations.
COST:
Not including the transformer and power source, the total cost of parts and materials was less than $50. Including the initial cost of the first unit the cost of three illuminators was less than $75 and I still have excess remaining materials.
Note Not shown here is the fiberoptic illuminator. That deserves its’ own presentation.
ILLUSTRATIONS:
























I made two illuminators for specific purposes. The white is for general transillumination. The royal blue is for study of coral polyps with green fluorescent protein bioluminescence. I hope that this keeps all of the Olympus BH2/BHS microscopes working for more years to come.
Just wait until you see the fiberoptic direct illuminator.
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