Wednesday, October 20, 2010

Repairing the "Unrepairable" Microscope

The school I teach at has a small number of microscopes used by our science classes. I also use them once a year for a lesson where I bring in a bunch of microcircuits made visible to let my students see what's on a chip directly. I also bring in a wafer and some dice (the microcircuit variety, not the Yahtzee variety) for the kids to see and handle.

The exhibits themselves range from a 1959 transistor with the top of the can cut off to reveal the chip and a 1965 dual op-amp similarly prepared to a 1st generation microprocessor to late 80's memory circuits. All together I have about six to eight things I can put under the microscopes that would be interesting to look at.

Since I've been with the school, one of the microscopes has had a label on it reading "Broken, Save for Parts" on it. Since there are only six microscopes, including this one, it means I have to spend time in class changing over each scope from one object to another. Fortunately I've gotten good at talking while focusing a scope and shifting the light and indicator around to the best position. But it would be awfully nice to have at least one more scope. Recently another of the scopes got damaged, reducing us to only four scopes. This is really too few, especially for our science classes.

I Can Fix That

Our science teacher found out I work on optics (I build telescopes as a hobby, in addition to my work with sensor systems professionally.) She asked if I'd be willing to take a look at our newly broken scope. I agreed, and suggested that I might take a look at the "parts only" scope as well, since neither of us knew what was wrong with it.

The office staff let us know that the other scope had been declared "unrepairable" by a scientific instrument repair service that had looked at it several years ago.

When I took a look at the "unrepairable" scope, the optics appeared to be in perfectly good condition. The adjustments and controls were likewise all in good condition. All I found was that the light built into the base did not turn on. I had a light handy, for my own scopes I prefer a light that isn't built into the base, that way I can just grab another light if one of the bulbs burns out when I'm in the middle of a job. More than half the time I'm looking at something opaque anyway, and when I do look at translucent samples I use a mirror as often as I use a lamp for a backlight.

I opened the base to the "unrepairable" scope, wondering what would prevent the light from being fixed. Perhaps a small fire from a prior fixture?

Since When Is A Bulb Replacement "Unrepairable"?

When I got inside there was nothing worse than an empty light socket. The previous light had burned out, been removed, and not been replaced. I could see why, in part. It was an odd sort of bulb. The base style is the same as that for an automotive type "1004" bulb. It's a bayonet mount with two contacts at the tip of the base rather than the usual one. The designation is BA15D. It's an unusual type of bulb, especially for 120V. They run from about $5 to $35 depending on how specialized your supplier is. But they're not unavailable, by any means.

Still, they're hard to come by for people used to picking up light bulbs at hardware and grocery stores, so I decided to replace the base with a more common screw base. A standard medium size screw base, as used on most incandescent lamps around the home, would be too large to fit in the microscope's base. A small "candelabra" base would fit handily, but I wanted to make sure it'd be easy to get lamps in the right range of brightness. Candelabra base bulbs of up to about 15W are easy to come by in a size that would fit. But above that they tend to be the larger "flame" shaped bulbs in the 25 to 40W range, which wouldn't fit properly.

So it came down to an "intermediate" size screw base. Bulbs for these are common at hardware stores and such, as "high intensity" lamp bulbs (in 40W), and as lamps for vacuum cleaners, appliances, and such. 20W to 40W are common.

You Can Get the Bulb, But Not Its Base

Now the problem was finding such a base. I checked several hardware stores and lighting stores, with no luck. They all sold bulbs to fit an intermediate base, but no actual lamp bases in that size. I checked Radio Shack, just on the off chance, and my prejudices about their current parts stocking were confirmed. I even considered using the halogen lamps with the loop and straight leads on them. While the lamps are readily available, once again the bases are not.

I went to several stores and looked at cheap lamps, looking for one I could cannibalize without paying too much for the privilege. No luck, the LED lamp rules there, and none were suitable for a microscope. Neither the light pattern nor the size would work.

Finally I tried yet another hardware store while I was in another nearby town. I was ready to give up on intermediate size and go with candelabra, and hope to find a 20 or 25W bulb to fit. They had a single bulb wired fixture with a candelabra screw base. It looked perfect. The fellow minding the shop floor mentioned a lighting store nearby that I hadn't been to, as well. So I bought the candelabra fixture, a 15W bulb that would fit it, and headed over to the other store.

There they had lamp components in parts drawers, a very promising sign! I found several different types of base, but all in candelabra or medium size. One of the workers there helped me look, but we didn't turn up an intermediate base. We did turn up an adapter to go from a candelabra base to an intermediate base, though. I got that and a 25W bulb to fit, then went home with the lot.

Once home, I test fit the new fixture in the base with duct tape. I pulled out a selection of slides, and selected one with a nice thick feather sample on it to test the light level. I started with the 15W bulb and a thick section of the feather. The 15W bulb illuminated it, but not as well as I would like for students. Student's eyes aren't trained to pick out details yet. They need things well illuminated to help them see what they're supposed to see.

Putting It Together

I put in the adapter and the 25W bulb. That worked perfectly. Bright enough, without being too bright, even with a bacterial sample on a slide. In fact, the bulb aligned with the reflector in the base better with the intermediate base adapter. So I removed the old fixture from its bracket. Prepped the bracket and plastic welded the new base's fixture into place. I cut out the old fixture's wires, desoldered one end from the light switch, soldered and spliced the new fixture in. When it was all done, it looked like it was supposed to be that way. I tested everything to check for operation and safety afterward.

Then I added some labels to describe how to change the bulb to the outside of the case, and what bulb to use.

Now the "unrepairable" microscope not only works great, but can be maintained by an ordinary person without calling the "scientific instrument repair" service.

Monday, October 4, 2010

Back on World of Warcraft

While the rest of the world is playing Starcraft II and free MMORPGs, I've just returned to World of Warcraft. Not only my own account, but three others for my family. After a two year hiatus, why am I back?


For some time now I've not had a good activity for when I'm too fried for anything serious. We don't get broadcast TV here, and satellite isn't worth the price. 300+ channels and nothing really worth watching. Normal broadcast channels cost extra. Thanks to my Congress passing bills to "protect" me, I can't get national network feeds over satellite any more, as I did about 10 years ago. Then I could watch shows I wanted to watch on my schedule, rather than being beholden to the "local" stations (the satellite companies consider Sacramento local to me, even though I'm about midway between there and Reno.)

Radio Static

Listening to radio is something I usually do while working on something else, so it's not an activity that's engaging enough when I just want mindless entertainment.

DVD and VHS Overfamiliarity

If I hadn't already watched my favorite "watch them anytime" disks and tapes to death, I suppose I could do that. There's a lot of material in Connections I/II/III, Day the Universe Changed, The Learning Company's Astronomy course, and several others. But when I get to where I can lip sync with them, it's time to find something else to do.


WoW is more fun with a group. Pick up groups aren't fun, for me. So I looked at WoW's charges with an eye toward "how does this compare to satellite TV?" I came to the conclusion that it's reasonable to spring for four accounts for the family to get my own built-in group.

My Account

I got an account about the time WoW was generally released to the public. I had some "real life" friends to play with, as well as friends who'd moved over from Everquest for the Mac. My kids played on my account when I didn't. They'd hot-seat, or I'd give play time as a reward or inducement to do homework or chores or whatever.

The Kid's Accounts

Then, as the kids got older (teens), they wanted their own accounts. I gave the green light, provided they saved enough money for their own retail box and six months of service. They both did so, and they could keep playing so long as they paid for it. After some time, they both decided they'd rather spend the money on other things. We suspended their accounts, and they went back to playing on my account.

Leaving Azeroth

Meanwhile, my various friends either left WoW or I lost track of them in real life as well as in-game. I ended up on a new server in a small casual guild. But I was mostly playing solo, I was losing interest, and the guild was dissolving. The community on that server just never really gelled. I considered moving to another server, but various other things were keeping me from playing much, so I deactivated the account about 18 months ago.

Return to Azeroth

Now I'm back. I reactivated my account, and had my daughters reactivate theirs. This time it's on my dime, so long as they keep up with homework and housework. Plus I got a fourth account. It's for my wife, who never played before.


My wife was once a non-gamer. But over the last few years she's enjoyed joining games--due in large part to our daughters. She's played tabletop RPGs like Traveller and Pathfinder and enjoyed them. We also play a lot of board games like Cosmic Encounter, Quirks, and Settlers of Cataan. It's a big change. I couldn't get her to play games before the kids came along.

Now we've got her on WoW with us. We played for about 3 hours this last weekend and had a good time. It was challenging for my wife, she's not familiar with computer RPGs, but everyone was patient. We had her roll up a hunter since they're pretty easy to play and a forgiving class. She managed to learn the basic controls, get around most of the newbie zone without getting too terribly lost, and made level 8 in her first session. She professes to have had a really good time.

Time Filler

Meanwhile, I've got a fried-brain spare time activity. This afternoon my youngest got through her homework quickly and did several chores--unasked!--so that she could play and get a character to one of the special little seasonal activities in WoW before it goes away for another year. I'll still have time for my hobbies--WoW doesn't replace actual things like electronics and telescope making for me. But when I'm not up for those, I won't be casting around aimlessly as much.

We won't be able to coordinate family schedules well enough to play more than perhaps once a week all together, but that will be enough. We have other family activities we do as well, like reading, that take some of that time. Right now we're working our way through Watership Down. Only I have read it before. We read for about 45 minutes this weekend before we jumped on to WoW. If we manage as much as a couple of hours a week together on WoW, that' good enough for me to justify the accounts.