Telescope Repairs-B&L 4000

As Secretary of the Astronomy Club on the campus, I recently came into possession of a Bausch & Lomb Criterion 4000. It is a Schmidt-Cassegrain telescope, with a 4" aperture, 1200mm focal length. A cassegrain reflector uses a combination of a primary concave mirror and a secondary convex mirror to form the image, thus giving the telescope its name. A schematic diagram of the telescope is given here.

Hugely popular when it first came, because of its portability, this model hasn't been in production for some time now. A good model for use in homes by amateurs, on terraces and gardens, it doesn't really qualify as too useful in outdoor conditions, with its table top stand and small size. However, because of lack of funds (ours is a new club), we think it is good enough for our use.
 So the first time we take it out on an observation session, we notice that whatever we do, we can't see anymore than just a white blob (yeah, we started with the moon). We figured it was a problem with focussing knob as it seemed too loose. When I googled about it, I found that its focussing knob was a common problem.
That was when we decided to open it.
Ideally, an instrument such as a telescope should be handled by experts, especially on repair jobs. But, then, such is youth!
So we, Co-ordinator of the club and myself, sat down to work with a couple of large pliers, a set of screw-drivers and a cutter, just in case. It does seem like too heavy duty equipment for an object so delicate, but trust me, we had use them all. After detaching the tube from its mount, we first unscrewed the focussing knob. It was mounted on a screw which had apparently disengaged from the mechanism inside it. We dismantled the tube. It was essentially made up of 3 parts, the tube, the primary mirror with the focus mechanism and the eyepiece. The screw of the focussing knob is used to rotate a shaft, which in turn rotates another screw, thus moving the primary concave mirror forward or backward. This adjustment of the mirror distances helps in focussing.
After re-engaging the mechanism, there was a slight problem of aligning all parts as before. A small tip would be to keep taking photographs of he arrangements in the telescope during opening it.
Finally, we tested it out, and got sharp image of the full moon. Only problem is stray reflections from the glass front of the tube, which I suppose is something we will have to live with.
And this way, I have a perfect gift for the club for the General Body Meeting tomorrow!

Astable MV using IC 555

In course of all those things I try to do in electronics, I have successfully constructed an astable multivibrator using the Timer IC 555 countless number of times. But this is one time I am really going to remember for quite some time.
For one, I actually paid attention to the arrangement of the circuit board. Whenever I assemble a circuit on a PCB, I only see the that wires go to right places, not how many times they are looping around the whole circuit. Though its really cumbersome to find a fault in the circuit then, my happily egoistic self never believed I could make a mistake. And luckily , I never did!
Secondly, this time the circuit didn't work...
Strange, but true. My shabbiest circuits work like a dream (Once, I actually hung a ckt assembled on breadboard, on a hook once, using the connecting wires), but the first time I try to make a neat circuit, the circuit doesn't work!
So getting back with the story, in my college,there is an M.Sc.(Tech.) programme, that is a 4-year, Undergraduate programme. Information System is currently the only stream in which this degree is offered. These people have a subject called Electrical & Electronics Theory, in the 2nd year (when we, in Electrical & Electronics Engg. stream haven't had any), where they have to make a project for evaluation. So these two guys in my hostel came up with a brilliant plan to make the buzzer system which can be activated by more than one switches, thus making it useful for quizzes and JAM sessions. Of course, one power source, 3-4 switches, one buzzer, a few resistors, simple enough ckt. But before they could figure this much out, someone suggested to them that it would be really "cool" to make two astable MVs on the same ckt board and use them to power the buzzer. So the two people who had never assembled a ckt on a PCB, ended up on my door-step with all the components and a ckt-diagram I knew by heart!
When I suggested the easier method, they told me that it would be too simple, and this one would look like some work has been put into it. So I agreed to help as I thought it would hardly be a 2-hour job at max, and frankly, I didn't wanna study. So 2 hours and 1 Domino's Pizza later(seriously guys, Domino's rock, and nothing helps you work more than a pizza! Even the pizza box was useful, ending up as my soldering iron holder), one of the circuits was ready, neatly made, with a separate line going for +Vcc and another one for ground and all connections, flat on the board, parallel to each other, ending on these two lines. I tested it, it worked and then I realised I had to make 2 ckts. So some minor changes, changed the position of buzzer, and started on the other one. When I tried to test the second one, it didn't work. More shockingly, even the first one didn't work now!!
So now I had 2 non-working astable MVs. Initially I thought its some problem with  the arrangement of the buzzer, as that was the only thing whose position had been changed. Well, I got to work, and though the neat ckt did make it easier to debug, I also found that I hadn't made some connections I wouldn't have forgotten otherwise. For instance, wiring pin 2 and pin 6 together. Oh, and I forgot to connect the buzzer to the ground too! Presence of a common grounding line on the ckt board meant I forgot connecting components to the line(this was purely carelessness, though).
Now even after finishing all connections, both the ckts didn't work. I tested continuity of every single point wrt to every other, and found nothing amiss, and was virtually at my wit's ends. As the project was started just a couple of days before the submission date, my friends were all for hard-wiring the battery to buzzer through 2 switches in parallel(which is what shoiul have been done in the first place!), but that would remain a mystery unsolved...
That night as I sat fiddling with the circuit, I just checked the continuity between ground terminal of the buzzer,to have something to do, and it showed no continuity! Though I could hardly believe it, I took up a wire, and directly connected the ground terminal of the buzzer to the negative of the battery, and tested the ckt. AND IT WORKED! Like a dream!
So there was the problem and the solution. On closer inspection, I found that because of some impurities on my soldering iron during soldering, the solder wasn't in contact with the ground wire. It just surrounded the wire, with a coat of non-conducting impurities between solder and the wire. When you solder from the top, molten solder clings to the iron, but impurities move down and evaporate. Here they formed the layer before evaporating.
So then, this time I properly connected the ground terminal to line, using a huge length of wire, and tonnes of solder. Just to be sure, I reconnected all the doubtful connections in my trademark style. After all, a shabby, working circuit is better than a non-working, neat circuit! And thankfully, the circuit still worked.
So I finally gift the ckt to my two friends, who unknowingly, taught me another lesson. And the instructor never checked the neatness of the ckt, just the working and was very impressed, from what I heard. Well, that way even the simpler one would have worked :/
However, I noticed one thing. I had used different set of values of resistors and capacitors for both circuits, and the sound produced by both on the same buzzer sounded different. Though I feel that is a result of different output frequencies, I am still searching for answers. Suggestion anyone??

Surgery on Macbook Batteries

Recently, one of my friends had a small problem with his Macbook trackpad. The trackpad button was getting pressed even with slight pressure, while just navigating. He suspected something pressurising the sensors from inside, and traced the problem to his bloated 6 cell Li-Po battery pack!
When we opened the battery, the screws simply popped out after a couple of turns of the screw-driver! We found all 6 cells bloated up. The battery is supposed to be 5 year old!!

Making the Cuts, Courtesy:TLS

We decided to puncture the outer covering of each cell slightly to let out the trapped gases, carefully so as to not damage anything inside it. So using a couple of paper cutters, we did just that, though, thanks to the super adhesive glue used by the manufacturers, we could only do that to 3 cells on one side.
After letting out the gases(which had a sweet, ester like smell to it), we covered the puncture marks with some insulation tape. The cells now dont show any sign of being handled by amateurs, the battery pack closed and got attached relatively easily(no popping screws atleast!!) and now the trackpad is back to normal. Happy Ending :)

Final Product, before screwing back, Courtesy:TLS

Only awaiting results on how long it runs without charging. If that is same as before, then we can say, "Operation Successful!" :P