From wardshrake@aol.com Sat Oct 29 01:56:50 PDT 1994 Article: 5162 of rec.games.video.arcade.collecting From: wardshrake@aol.com (WardShrake) Newsgroups: rec.games.video.arcade.collecting Subject: TECH TIPS: more of 'em! ------------------------------------- ON CLEANING PARTS BEFORE SOLDERING ------------------------------------- Part of a successful, electrically sound solder joint is getting the two seperate parts clean before trying to solder them together. This is similar to "glueing" almost anything together; it works best when both parts have clean surfaces to join. But how do you clean them? It depends on what the part is. Edge connector surfaces, and big, fat, bare-metal traces on PC boards are relatively easy to clean. A pencil eraser takes off most crud, no problem, with minimal damage to the part. The plastic versions of Scotchbrite house cleaning parts work too, but may be too rough; try the eraser first. (Watch the thin gold plating on edge connectors, when cleaning. It is really, really thin in nearly all cases; rub easily and carefully, even with a pencil eraser!) Also, erasers on the actual end of a pencil need extra care; you may scratch the part, if the eraser head is worn down to the metal ring. I prefer the large, flat seperate erasers.) Bigger parts can be cleaned with the plastic-type Brillo pads, as mentioned, if you are careful enough. (Other part cleaning suggestions welcome, of course, if you have a better/favorite way.) ------------------------ ON BENT IC PINS (LEGS) ------------------------ More trips to Radio Shack, coming up; do they know you by your first name? Not yet? This time, ask for something called an "IC pin straightener," or something close to that. I can't find the blankety-blank RS part number at the moment. For now, make them prove their "We have answers" slogan. (Does that include "I don't know?" Technically, thats an answer, right? Hee, hee! Couldn't resist.) Anyway, the part is in there, somewhere, or I'm going senile earlier than expected. Basically, it is just a simple black, plastic square, with only two moving parts. It has a long, thin center section, with two spring-loaded outer pieces attached to it. You insert an IC flat into it, with the legs on each side fitting into the gap between the center piece and the outer sections. When you squeeze the device (in your hand, not a vise or anything!), the legs are forced inward, straightening them. By the way, there are two sides, with different leg spacings, (0.3 and 0.6 inch) to accomodate the two common DIP chip package widths; use the correct side. This may all sound pointless, probably, to those who haven't played with IC's much yet. What you may not be aware of is that IC's come from the factory with their little legs pushed slightly outward, like an awkward calf. Good luck, if you don't know this, and you try to fit the IC into a board or a socket as is! Until you straighten the legs (really simple to do, no problems) you'll likely be frustrated no end and may end up with a real need to know how to straighten badly bent IC legs! For seriously bent legs, you will have to (carefully now!) bend each leg almost straight with a pair of small pliers or tweezers, one at a time, to get each of them into the ballpark. Then use the official straightening tool to get them all lined up nice and neat. They can take a few bends back and forth, but eventually metal fatigue sets in and the little buggers break off. Don't be overly paranoid about it, but do be careful. One advanced tip: once you are confident in this skill, you can place a chip on its side with one row of legs down flat, on a flat surface. By gently rolling the chip inward, you can get all the legs in a fairly neat, straight row. Just be careful, and roll it slowly, without using too much pressure. However, the official straightening tool is still recommended. The tool does have one mysterious screw set into its body, for no apparent reason. See the anti-static section, for why. (It grounds the tool, somewhat like a miniature lightning rod, to protect static-sensitive IC's.) -------------------------------------------------------- ON GROUNDING PRECAUTIONS, FOR ANTI-STATIC PROTECTION -------------------------------------------------------- Bought any Radio Shack stock yet? Maybe you should .... I'm about to tell you to go down there and buy more stuff! (They are accessible to almost everyone; this is why I keep picking on them instead of other companies, which may also have fine parts.) This time, get yourself a "Static-draining wrist strap," part number #276-2397. (Is anyone checking these numbers, to keep me honest? I hope so!) What this part does is makes sure your body is at electrical ground potential, so that any potential static charges that might have built up on you, go somewhere safe (like earth ground) instead of going through your chips or board as you work. Think of it as a lightning rod, I guess; that is sort of accurate. One end of it wraps around your wrist, and the other end connects to the EARTH GROUND of your house's electrical system. (The center, round pin on U.S. wall plugs, NOT one of the two flat, AC pins. This is very important: whatever you do, don't accidentally plug yourself into a 120 volt wall outlet! Better an electrocuted PC board, than you, right?! Skip it altogether, for your own safety, if you are unsure of where your "earth ground" is!) For your info, some IC's are more tolerant than others. CMOS chips are especially fragile this way, due to their makeup and the fact that they operate on teeny, tiny amounts of current. They really, really don't like even mini "lightning bolts" cruising through their delicate circuitry! This is a good device to have around, and recommended. But if you don't have one of these, there are alternatives. At the very least, be sure to ground yourself once in awhile before and/or while working around IC's, by touching a (safe, please!) metal chassis ground surface for a few seconds, to drain static through the chassis ground, to the earth ground. This is mostly for us lazy types, those willing to take unneeded chances. Even then, only for some quick, easy fixes like gently pushing on an IC body to reseat it, with power turned completely off. (Never, ever work on any circuit, for any reason, with it plugged in, for safety!) If you don't like being strapped to a worktable, you may find an anti-static pad at a computer store. These do basically the same thing as a strap, but are more aesthetically pleasing and less restrictive. They just sit on your table, not chain you to it. They are supposed to keep you from killing your computer keyboard via static, which I think is a solution to a non-problem, but whatever. (Can you imagine all the jokes, if some boss type tried to "chain" workers to their desks, using the cruder-but-more-effective anti-static wrist straps? "What a slave-driver, etc, etc. For that reason, I can see why the more politically correct versions exist!) -------------------------------- MORE COOL TOOLS I FORGOT ABOUT -------------------------------- I finally found the number for the "Double-hand holder," which holds small parts while you work on them; #64-2093 ($9.99). I use mine constantly. Wire-stripping is something you'll end up doing tons of. (It probably deserves a section of its own. In the final version, maybe I'll do that.) For now, I'll try to save you endless wires-accidentally-snipped-off-too-short frustrations, by suggesting Radio Shack's best (in my opinion) wire stripping tools. Best for general use (8 to 22 gauge) is part number 64-1919, at $11.99 each. (It used to be my favorite.) Best for any one wire gauge at a time is the very inexpensive, user-adjustable part number 64-2129, at $2.99 each; wonderful for small wires, which others have problems with. On stripping / tinning wires: I always strip a bit farther back than I really need (more bare wire exposed). When I tin the wire end, any excess solder blobs can be slid all the way down, and cut off when I trim the bare wire to its real length. Till next time, have fun, be safe, and thanks for putting up with me! Ward Shrake wardshrake@aol.com w.shrake@genie.geis.com