AO Starlite external Illuminator led retrofit.

[apochronaut]

The AO Starlite illuminator series is a ubiquitous stereo microscope illuminator series in North America. After 1985, they were branded Reichert, subsequent to the decision by AO's parent company , Cambridge Instruments , to carry the company into the future under that brand. It was also marketed elsewhere under the Reichert label by C. Reichert of Vienna. The main difference between them was that the European version was 220 v. There were various models but the differences were due to only the type of power supply and the method by which the actual illuminator unit was mounted or used.
I mentioned in this thread, viewtopic.php?f=24&t=8286 , the desire to retrofit one of these to led, in order to boost it's marginal 17.8 watt output. I do have the capacity to gang these and filter them, so I am not unhappy with it's performance as a tungsten illuminator but having the extra oomph of a brighter light is always useful in microscopy. The harshness of the led can always be modulated by blending with tungsten illumination.
The Starlite uses a GE 1460 17.8 watt tungsten lamp. The lamp has a similar base to a standard Ba15d double contact base, or that of a car taillight/brakelight composite type bulb but instead of having a pair of locking earpins, it has a flange soldered to the base with 3 teardrop shaped slots that lock when the bulb is turned . This is a P30D base. Also, instead of the two contacts carrying separate signals as in a car; one for the tailight and one for the brakelight, with a grounded base, the two pins on the 1460 are hot and return with an ungrounded base. The Starlite is powered by a 6v. power supply.
So I ordered a pair of cheap led 6v. motorbike head lamps. I would have preferred a bulb with a single pin but the output of all of those available easily, is pretty low. I was hoping a headlamp would be better. They are advertising 35 watt equivalent or thereabouts.
1) Shows the starlite illuminator lamp housing. The two chrome plated slot screws are removed to separate it's halves.
2) The bulb section after separation.
3) Closeup of the bulb mounted in it's socket
4) Bulb removal tool installed on the bulb. This tool is sometimes necessary to remove stubborn bulbs. It helps avoid separating the glass envelope from it's base. It will be useless for installing the new led bulb. There is a small indent on the side of the locking flange, allowing for installation with the blade of a screwdriver.
5) Bulb removed.

[apochronaut]

6) The two bulbs side by side. Clearly the headlamp base is much larger but the width and length of the the led section looks to be close to perfect.
7) The two bulbs separated. The glass envelope separated easily from the base of the 1460 bulb leaving the two wires intact. The led bulb 's method of attachment was unknown. Some are threaded together, some are glued. This one turned out to be glued and only a very small amount of prying, separated it. The solder joints to the circuit board must have been terrible because the wires came off with no effort.
The led headlamp uses a very primitive low beam technology. Low beams are usually lower in wattage but also incorporate a lower beam angle, accomplished by the relative position of the emitter to the facets in the lens. This one simply uses a secondary signal running through a resistor, visible in the picture, which dims the lamp.
8) The two desired parts of the intended bulb. The P30d base and the led headlamp emitter. The ground for the led unit is wrapped over the plastic rim of the led section and tucked under the metal surround of the base, making a crude physical ground. Straightening it made a good connection point for one of the wires coming through the P30d base. The other goes to the solder point that the two hot wires of the high and low beams were connected to.
9) More vertical view of same.
10) The two parts mated together. The O.D. of the base is just smaller than the I.D. of the emitter unit allowing the base to just nicely be epoxied into the the emitter unit.

[apochronaut]

11) The original bulb has a registration. The locking pins are situated at the apexes of an isosceles triangle, so that the two contacts are turned into the correct alignment with the contacts in the base. Removing the entire base, not just the flange, maintains the registration and the position of the emitter section is irrelevant.
12) The wires attached to the P30d base are soldered through two tiny copper washers, which serve as the contacts. The wires are shown desoldered here.
13) The two copper contacts will have solder clinging to their central holes after desoldering. Gripping them in small vice grips at their lip, heating the solder and then giving them a quick shake or two, frees the solder from the central holes , restoring them to washer status. The two wires from the P30d base are shown soldered to the hot and ground sites on the led circuit board. The board has a small + marked on it but the site was evident by the solder connections visible anyway.
14) The assembled and epoxied bulb with the wires sticking through the base. The desoldered contacts are to the left along with the small drops of solder that were shaken off of them.
15) Contacts have been soldered back onto the wires through the base, filed smooth and the bulb installed in the socket. The bulb is shown with the setting on the transformer at 4.5 v. Turning it up to 6.5 produced a predictable increase in illumination.
The plastic surround or lip of the led section was large enough to impede the entry of the locking pins upon installation. This required about 5 minutes of filing on the plastic collar to make 3 flattened reliefs for the pins , prior to installation of the bulb.
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[MichaelG.]

Nicely documented, thanks.

I’m interested, and a little surprised, to see you converting to LED
... If my memory serves; you have previously been rather anti

Hopefully, the newer/warmer versions are to your taste.

MichaelG.

[apochronaut]

You are kind of right in that. Leds for microscopy stink in my opinion. Sure , one can trot out examples to the contrary; $10,000 microscopes that offer a more expensive led option, one or two diy set ups that might work o.k. or the possibilities with products from companies like Nichia. The thing is though; if your illumination requirements are high, as is the case for a lot of what I do, where I use 60-125X objectives a fair amount, phase and DF , inexpensive led retrofits are a miserable failure. Collimating them is a nightmare and since I can buy a 100 watt halogen bulb for 3.00, why even waste my time on leds? I'm not really anti-led, I'm more anti the human preoccupation with pop culture, grabbing onto anything new before it has been proven to be valuable. I spent most of my working life in the sun. The sun is a fire, it produces almost all of the visible spectrum. Tungsten filaments are a fire. I'm a cave man.

In this particular instance, I crawled out of my cave one night and found that my Starlite was too dim. Must be failing eyesight from staring at the sun. I thought I could utilize led for it's two beneficial qualities; potentially high illumination without high temperature and to get rid of that annoying blue light, I can always blend. There is a 35 watt tungsten bulb that I might be able to retrofit into that lamp housing but I don't think the housing could take the heat. 18 watts is just to low, once one zooms up or dials up 40X .

Anyway. The lamp is putting out light but it is clearly all over the place. My next task is to build a reflector to capture the side radiating light or change over to use a single high lumens cree chip.

[geo_man]

Very interesting description and photos, thanks! It would be great if you came up with an easy/effective adaptation. Martin Microscopes sells a "NichoLED" illuminator for $295. Don't know how well it works. Cheers!

[MicroBob]

Hi Phil,
interesting project and welcome in front of the cave! For high power illumination I like Cree XHP 50 and 70 LEDS. They have 4 small emitters very close to each other and offer 18 or 32 Watts.
I too have a stereo microscope illuminator to improve, for a nive and versatile Meopta stereo with objective sets up to 10x. The illuminator is not much more than pencil thickness and uses a better bicycle bulb! Since it is nicely made I will try to put a 10W LED into it.
The last LED illuminator was for my Zeiss Phomi 1 for the epi fluorescence set. I had a gap to just 24mm to squeeze the light in from the side. This works well with a warm white XHP 50. A cold white version would be better for the blue excitation I have used so far.

What I think about is to combine a warm white LED with a blue-green one to acheive a continuous spectrum with comparatively little heat emission.

Bob

[MichaelG.]

Having found a nice copy of a catalogue to peruse:
https://mightyohm.com/wiki/_media/resou ... atalog.pdf
... I am a little concerned about your choice of LED lamp

Although I am not familiar with the Starlite illuminator, it seems clear that it uses fixed pre-focused bulb and condenser elements. ... So: Whilst your motorcycle bulb might produce a lot of light, most of it will be in the wrong place.

46B1720A-2FF5-4EFF-ADEC-3D87469640DC.jpeg (154.71 KiB) Viewed 4948 times

Your installation does look very neat and powerful, but I would respectfully suggest that you should get much better results from a compact LED source placed in the same location as the original filament.
... and I think you already know that

Anyway. The lamp is putting out light but it is clearly all over the place. My next task is to build a reflector to capture the side radiating light or change over to use a single high lumens cree chip.

MichaelG.
.

P.S. sorry about the mysterious filename for the attached image ... there seems to be some strange incompatibility between iPad OS and the forum software.