I found my old 50-900 zoom microscope while cleaning out my attic, but I don't remember how to turn the light on and yes I put batteries in it.

Email nikoninstruments(at)nikon(dot)net with some pictures of your microscope and I'll see if we can ID it. Make sure the pics are bright enough and in focus and at a wide enough angle to get a good look at it. Nikon Instruments Microscopes and Imaging Systems

contact tasco.
try ebay for a month (search various combinations of keywords). notify by email.
21.january.2015

sorry about that.
we can not see your screen so any answers are wrong or 100x too long.
NO BOOT has over 20 causes.
the top 3 are
1: all batteries in the PC are bad even the coin cell.
2: bad HDD.
3: infected OS. (running virus magnet XP?)
or worse ,

Olympus makes good microscopes so you have done well and stereo microscopes are so much nicer to use than singles. As far as cleaning the lenses goes, buy a good quality camera lens blower brush and also a can of compressed air like the ones used for computers. Blow any loose dust hairs etc off with the can of air and then use the brush for anything remaining. If there are fingerprints or grease on the lenses then clean them using camera lens cleaning fluid and lens tissue but make sure all debris and dust are removed first or you may scratch the lenses. In general try not to use anything more than air and a brush unless absolutely necessary. Another option for removing fingerprints etc is to use a "lens pen" with caution. The ones sold for cameras work well but may be too large. They make some smaller ones for cleaning camera sensors and those might work better for the relatively small microscope lenses or just cut the regular lens pen disk to make it smaller. It is just as important to make sure the lens is dust/debris free when using the lens pens.
Low power stereo microscopes often allow you to put on a single magnifier lens in front of the main objectives to increase magnification. Do a bit of searching to find what are options for your model.

Contact Tasco they may be able to help:

9200 Cody Overland Park, KS 66214

Most of the Tasco microscopes that operated on batteries used AA batteries.

sometimes when a battery causes corrosion inside something, you can clean off the springs or contacts where the battery goes. if i can, when that stuff happens i use sandpaper or something like that to clean the contacts. you cant always get sandpaper where you need it though. just try to find something to like scrape stuff off if its on there

Have an electrician check the circuit. It is probably just a faulty contact, blown fuse or bad lightbulb.

Same problem, tried flipping it every which way with no luck - both the light itself and the arm that hold it. Finally, when trying to change the batteries, I noticed that they battery housing was odd: usually the positive end of the battery is against the node, and the negative end against the spring. This is true for one of the batteries, but for the other one has to turn it backwards, so that the positive end is against the spring. This is the only time I have seen a battery go in that way, and so naturally I had not looked for -/+ labels, but had just put the batteries in the housing in the way one would assume they go. When I changed the one around (and it was labeled that way), it solved the problem and the light came on. I don't know if I just got lucky, but you might as well try and see if it works for you.