New LEDs for your microscope - tardigrade friendly cold light! (II)
From 230V tardigrade barbecue to clever LED microscope illumination

In the October issue we had discussed a modern LED variant for vintage microscopes. The advantages are a standardized thread, high intensity and little heat. Just have a look at #4 below: it has a 14 mm thread which can be used in many vintage microscope illumination housings and its light projection capabilities are perfectly fine for microscopy.

Fig. 1: The metamorphosis of ancient high voltage bulbs to high performance LED lights
(1)  Classical E14 thread 230 V bulb with a power of 25 W. Be warned: this is a tardigrade (heat) killer! (109)
(2)  An early E14 LED lamp, with the light radiating to all (most wrong) sides (10 ... 20)
(3)  A more modern, matte LED light with a little bit more power (30)
(4)  Our present favorite - a LED lamp with 24 tiny LEDs elements. It is able to direct most of its light into the microscope optics - perfect! (112)
The red numbers in brackets are indicating the approximate light output of the respective products.

Fig. 2 is a close-up view illustrating the inner structure of bulb #4 made up of 24 single LED elements arranged in rows and columns, packed on a rather small surface area.

Fig.2: Close-up view of bulb #4 (under low current condition - with full power the LED elements appear to merge into a single rectangular area).

And as already pointed out this lamp has a standard E14 (14 mm) bulb thread, i.e. the thread of the samller European bulbs. As a consequence the old-fashioned high voltage E14 bulbs can be simply plug&play exchanged against modern E14 LED bulbs - perfectly reversibly! Let's demonstrate this on the basis of a vintage Hertel & Reuss microscope:

Fig. 3: Hertel & Reuss microscope, serial no. 93380, built around 1970. Binocular, with photo tube (okay: let's accept the term "trinocular" as well :-). Low voltage illumination by means of a massive transformer delivering 35 W illumination power, a value which might appear competitive even today, in our miraculous LED era. According to the contemporary  Hertel & Reuss nomenclature this instrument can be labelled as a "CN-hF-BINfo-VK-ZT" (to be deciphered as: series C-new/high stand/binocular with photo tube/rectangular table/condenser height adjustable by rack and pinion). The  list price of a roughly comparable CN-hF-instrument in the year 1974 added up to DM 1658.-- (net price, without taxes) which can be roughly translated to a present price of US $2,000. The instrument shown here was acquired via Ebay in 2015 for a ridiculous price below 100 US $. The seller had no intention to perform rudimentary cleaning and didn't intend to place this jewel into appropriate light. Moreover we have an added bonus of a ready-to-LED switch option.

Fig. 4: Hertel & Reuss microscope, back side view with removed lamp housing. Please note the old fashioned E14 filament lamp.

Now we can simply replace the old-fashioned bulb by the modern E14 LED bulb. That's it. The geometry and lightpath are quite okay. No soldering! Moreover this is fully reversible and you can return to your beloved E14 furnace in case you should want to.

© Text, images and video clips by  Martin Mach  (webmaster@baertierchen.de). The Water Bear web base is a licensed and revised version of the German language monthly magazine  Bärtierchen-Journal . Style and grammar amendments by native speakers are warmly welcomed. Main Page