Epistar microscopes

[jorymil]

Hi everyone,

After doing some basic reflected-light stuff with my AO 20 microscope, I decided to buy a used epi scope to get some better illumination at higher magnifications. I ended up with a used AO 1860 Epistar scope (reflected only) for a fairly reasonable price, plus an old AO 120 that I might use as a parts donor or to replace my 20.

The first hurdle: the scope came with an odd, four-prong power plug, square in cross section. Anyone seen one of these before?

https://i.ebayimg.com/images/g/cNUAAOSw ... l1600.webp

John

[Scarodactyl]

Yeah, that's an odd standard meant for a particular power supply (presumably ao you din't accidentally plug it into the wrong one).

[jorymil]

Presumably I need a step-down transformer of some sort; just haven't seen the correct model floating around in any of the manuals. Internally, the cabling seems to be 2-conductor, for what that's worth. I plan on examining the wiring as soon as I can find my 7/64 hex key (I count 8 different sizes of hex keys used so far!).

[Scarodactyl]

Oddly I think Nikon (?) used a similar cable plus which is what I was thinking of.

[jorymil]

Ok, figured it out. The bulb in question is a GE 1974, AO part number 1858. 6V, 20W, so a transformer is needed. The mechanical connections on these things are... less than stellar. Loose crimps, exposed leads, no fuse that I could see. I have a transformer on the way, and looks like I need a new bulb.

Snapshots for the curious: https://drive.google.com/drive/folders/ ... tW3iDeSs7d

[jorymil]

Anyone do an LED swap of these? Halogen bulbs aren't cheap, and the build quality of the connectors was poor.

[wabutter]

That is not the original plug assembly that was used on the 1860. The original power supply was built into the base and controlled by the knob on the front of the base. Does yours have a large stage for wafer inspection or a smaller stage suitable for looking at metallurgical samples? FYI, I have a set of 5x 10x 20x, 40x BF/DF objectives from the 2560 Epistar. PM me if you have any questions.
Wayne

[Scarodactyl]

Halogen bulbs should still be cheap if sourced right but LED replacements are doable. I use a CREE x-pl led in my epi illuminator and it's worked great for me. But it will take some careful DIYing, there aren't great drop in replacements.

[PeteM]

. . . Anyone seen one of these before? . . .

John

John, They're "Cinch-Jones" or "Jones" connectors. You could do a search for compatible parts.

That said, I'd be inclined to swap out the Jones connector and use a double banana plug. It will be cheaper, entirely adequate voltage and amp-wise, and compatible with many power supplies. Given a mystery lamp or mystery power supply, I'll often retrofit a double banana jack or plug.

Or, as noted above, do a LED conversion.

[jorymil]

Hi all -

I'm just ignoring the cinch-jones connector for now and focusing (sorry) on the bulb. My scope did not come with the base switch, nor the full stage, but I'm actually OK with that: the scope was cheap, and came with 10x, 20x, and 40x epi objectives, which are pricey on their own. Also have a 6.5x on the way.

Turns out the original bulb uses a G4 pin base, so I bought some 3W LED bulbs, wirewound resistors, and bulb sockets off Amazon. I can at least check for bulb fit before the holidays; hoping to whip up a quick POC 12V circuit by New Year's.

[jorymil]

That said, I'd be inclined to swap out the Jones connector and use a double banana plug. It will be cheaper, entirely adequate voltage and amp-wise, and compatible with many power supplies. Given a mystery lamp or mystery power supply, I'll often retrofit a double banana jack or plug.

Funny you should mention that. I picked up some banana jacks last night for another project, and I have spares! For this, will probably just use a barrel jack, though: I have a lot of them laying around from various wall warts I've collected over the years. Network switches and wireless routers are cheap 12V parts sources.

[jorymil]

No dice on my first LED replacement, unfortunately. The diameter of the replacement bulb was too large by a few mm. The mounting/retaining mechanism is just a plastic ring with two indentations for the bayonet portion of the original bulb. While it might be possible to remove or replace the mounting fixture, best to stay as close to stock as I can before breaking out the 3d printer (CAD skills are fairly weak).

Original bulb dimensions (see gdrive link in previous post for photos):
Base diameter (non-bayonet): 12.6 mm
Base diameter (at bayonet): 15.0 mm
Bulb diameter (at tip): 9.7 mm
Bulb diameter (at base): 10.8 mm
Bulb height: 13.8 mm
Base height: 6.4 mm

This doesn't seem too outrageous to fit; have one more set of bulbs coming tomorrow that _should_ work; we'll see if I can test before the holiday break.

[Scarodactyl]

If you want best performance these aren't the best approach. You'll need to use a single die emitter on a heat sink positioned about where the halogen filament was. It is a lot more involved though.

[jorymil]

For sure. The collimating lenses were probably designed around having a point source of light where the filament would go, so the single-die LED makes sense. If you have some CAD/STL files for a retrofit, that'd help immensely. I'd very much like to travel that road, but for now, time constraints mean I just need to use off-the-shelf components.

What surprised me was that the original design didn't have a reflector built in, so probably 75% of the light would have been wasted anyhow. It looks like newer Epistar models (2560) had a slightly revised design that probably accounted for this, and also allowed for fiber-optic illumination, for example:

https://spwindustrial.com/reichert-epis ... KBEALw_wcB

[jorymil]

Got the new LED in last night: https://www.amazon.com/gp/aw/d/B08YMHQB ... asin_title

It is _just_ narrow enough to fit through the original bulb socket. It's a little long for ideal light placement; a little of the bulb still protrudes through the bottom. As there's no reflector built into the original scope, a significant amount of light is emitted out the rear of the chassis.

I'm not sure a series resistor is actually needed, as there's an SMT resistor on the package. Will have to measure voltages and currents after the holidays. Given the limitations of the original chassis design (no reflector to direct light source), a full redesign with a directed light source will be needed if I want to improve performance significantly. I'll post those results in the DIY section as time permits.