TimeFracture Lab Notes.
Here are some of my thoughts on home laboratories, and on lab equipment such as test instruments and tools.
While my own laboratory is in a basement, it’s spacious, well lighted, and well ventilated; a comfortable place to work for long periods of time.
I have a vinyl floor in my lab. Unless it’s made of hardwood, the lab floor really needs to be covered. Bare, unsealed concrete produces dust. Carpet is unsatisfactory because it’s hard to clean (you’ll splash solder and solvents on it occasionally) and it can cause severe problems with ESD (electrostatic discharge). Should you choose vinyl or linoleum, though, don’t make the same mistake I did--be sure to select a color or pattern that allows you to see parts after you drop them on the floor. My floor-covering is certainly attractive, but when I drop a lock-washer, I can never seem to find it again!
After years of working on ordinary tables, I built a serious laboratory test bench with an equipment shelf, an under-shelf lamp, and lots of convenience outlets. I am amazed at how this new bench has facilitated my work, and I seriously regret not having built it decades ago! The bench is 72 inches wide and 35 inches deep, with its work-surface 32 inches above the floor. After much thought, I made the equipment shelf 20 inches above the work-surface and 18 inches deep; these dimensions have turned out to be just right for me. There are two 10-outlet Wiremold power strips on the bench; one on the work-surface, and one underneath it for plugging in all of the gear on the equipment shelf.
In my lab, all non-portable test equipment not on the bench equipment shelf is mounted in 19-inch rack cabinets. The old PDP cabinets made by Digital Equipment Corp. (DEC) are particularly convenient, as their side-panels lift right off and allow easy access to the interior.
If you have woodworking or metalworking tools in your lab, or if you have a project that produces noise or which generates powerful electric or magnetic fields, you should isolate them from where you keep your test bench. Perhaps the best solution is to have them in a separate room, as I do.
I have a large metal cabinet in which I store shop chemicals and consumable items. I also store small, fragile, or sensitive items, such as circuit boards under development, in there. This way, I can set projects aside (that is, off of the bench) without having to worry about them being exposed on some table-top and gathering dust, or possibly being accidentally damaged.
You should provide your lab with a door you can close and lock. You’ll often want to have some peace and quiet, or to exclude pets and small children for reasons of safety.
One thing I regret not having in my lab is a sink. Running water is really useful for things like wetting soldering sponges, cooling high-power lasers, and just generally cleaning things up…
Don’t forget the bookshelf and the chalk-board!
In my opinion, there are two indispensable items of test equipment--a portable 3½ -digit digital multimeter, and an oscilloscope.
My DMM is a Fluke model 87. There is a wide variety of accessories available for it; high-voltage probes, current transformers, etc.
If you work with Tesla coils or similar “destructive” projects, you might consider getting a second, cheaper “sacrificial” DMM to use around them! I have seen imported DMMs selling for less than $10.
There are highly precise “bench” DMMs available, such as as Agilent’s 6½ -digit 34401A and Fluke’s 5-digit model 45. These are specialized instruments for the analogue circuit development laboratory, and they are probably overkill for hobbyist use.
An analogue VOM, such as the Simpson 260, is useful for measurements in which you are “peaking,” “nulling,” or looking at trends.
There’s never been a better time to buy an oscilloscope. A suitable new one will cost at least $1000, but good used instruments are available from on-line auctions for pennies on the original dollar! For example, the Tektronix 7834 plug-in storage ‘scope cost over $13,000 in 1986, but I recently bought one on eBay for $250--including a full complement of plug-in timebases and preamps.
Make sure that you buy an instrument-grade 'scope. Eico, Heathkit, and many commercial manufacturers (Hickok, RCA, B&K, etc.) made millions of service-type 'scopes that do not have triggered horizontal sweeps or calibrated vertical amplifiers. These units are inadequate for making serious measurements.
I wouldn’t buy any ‘scope older than around 20 years old or so. While it pains me to say so, you should probably avoid instruments such as the Tektronix 530/540 series and the 560 series unless you are a collector specifically interested in them for their own sake. These are magnificent ‘scopes, brilliantly designed and beautifully built, but let’s face it-- they are now ancient. Many of their components (such as electrolytic capacitors) are so old that they are becoming seriously unreliable, and some of their plastic materials (such as the potentiometer shaft couplings in the plug-in preamps) are literally crumbling to dust.
For general hobby use, I recommend that you get a dual-trace analogue or digital ‘scope of fairly recent vintage, having a bandwidth of 50 MHz or better. I found a Tektronix 2213 portable (analogue dual-trace, 60 MHz) for $120.
My bench ‘scope is a Hewlett-Packard 54602B (digital), which has four input channels and a bandwidth of 150 MHz. I bought it new in the early ‘90’s; spending entirely too much money on it--online auctions like eBay had yet to be established.
You’ll need probes for your ‘scope; one for each channel and another for the external trigger input. The general-purpose passive probe has 10:1 attenuation, a specified frequency response, and a “compensation” adjustment for matching it to the input impedance and capacitance of the ‘scope. Make sure that the probes you buy will match your specific instrument! I recommend also that you buy new probes. Used ones are too often broken, erratic, or missing essential accessories (such as the ground lead). New probes are generally available at reasonable prices, still sealed in their protective bags, from sources such as eBay. Take care of them and they will last a lifetime.
There are many other instruments which are useful but not necessarily essential.
Regulated bench-top power supplies are particularly convenient. They may be used to operate breadboards, and partially-completed projects whose dedicated power sources have not yet been arranged. My “bench” power supplies are mounted in a roll-around rack cabinet that I simply wheel over to wherever I need it; there are two 0-40V, 10A supplies, a 0-500V, 200mA supply, AC tube filament supplies, and a 0-30kV, 20mA supply!
I have several frequency counters. My bench instrument is an HP 5328AF (500 MHz) “universal” counter. Another fine unit is the HP 5245L, an older solid-state 50 MHz counter having a Nixie® tube display and an oven-stabilized crystal oscillator. These are plentiful, and they are sufficiently inexpensive (~$35 to $100, with plug-ins) that dedicated units may be left wherever they are needed, as I have done in my Time and Frequency rack and in my cyclotron support equipment rack.
Signal and pulse generators often prove useful. You’ll want gear that spans your desired frequency range. I have an HP 200AB audio signal generator, an HP 3300A function generator, and a Tektronix 191 high-frequency signal generator; my frequency capability extends from 10 mHz to about 100 MHz (with a big hole from 100 kHz to 350 kHz!).
If you do a lot of digital work, you may want a logic analyzer. This instrument is like an oscilloscope having many dedicated logic-level input channels and a plethora of triggering options. LAs are plentifully available as surplus, at low cost, but watch out--they are often missing their test leads! My HP 1630A logic analyzer arrived with its probe pods but with no leads; replacements were no longer available from HP and I had to kluge up my own.
An instrument which would be quite useful to the hobbyist, if it were only affordable, is the spectrum analyzer. Where the oscilloscope presents a time-domain representation of signals, the SA presents a frequency-domain representation. Unfortunately, its high cost (tens of thousands of dollars for a good instrument) generally places it beyond reach of any but governments and large corporations. As with ‘scopes, surplus units are often available at significantly lower cost, but their awesome complexity and difficulty-of-repair makes them a daunting purchase.
Advanced digital techniques may someday make the spectrum analyzer affordable for general use.
Test instruments from surplus stores or on-line auctions seldom come with manuals. Fortunately, there are many on-line sources for instrument manuals at this time, some of them free of charge (for example, see the BAMA [Boat Anchor Manual Archive] Web-site).
Of course, to get power and signals from where they are to where they must go, you need a selection of test leads, patch cords, jumpers, alligator clips, cables, and connector adapters.
I spend more time holding a soldering iron than any other single tool in my lab.
Choosing a soldering iron turns out not to be a trivial task. It seems that every manufacturer of soldering equipment out there makes an absolutely bewildering variety of irons, stations, and tips; the myriad components are usually poorly specified and are completely non-interchangeable. Do yourself a favor--after you find something you like, write down the part numbers of your preferred tips and accessories so that when it comes time to get new ones, you won’t have to launch a major research program just to identify the proper parts…
Soldering irons are often available with an optional “burn-resistant” power cord; get that, if possible.
For 30 years, my preferred soldering iron was the Ungar model 7500 “Standard Line,” with a 1237S heater (33 watts) and either a PL113 (chisel) or PL114 (micro-spade) thread-on tip. The tips, which have steps in size along their length, were iron-clad and tinnable all over their surfaces--when soldering a small connection I would use the very end of the tip, and when soldering something bigger (a terminal lug, say) I could use a larger-diameter place higher up the “shank.” But after Weller acquired Ungar (sob!), they changed the design of the tips, which are now clad only on their ends. This seriously compromises the effectiveness of the iron.
At present I use a Weller EC1002 temperature-controlled soldering station with an EC1201A (40 watt) iron for small soldering tasks, and a Weller W100P-3 (100 watt) self-contained iron for larger ones. The tips for the 40W iron are series “ET,” and for the big 100W iron series “CT.”
The big Weller guns (100-260 watts!) are occasionally useful for really large tasks, like soldering copper strap, heavy braid, or brass tubing.
My preferred solder is Kester “44,” 63% tin and 37% lead. This is a rosin-core eutectic solder. I remove the flux with acid brushes, and isopropyl alcohol dispensed from a Menda pump-bowl solvent bottle.
Use silver-bearing solder (2-3% silver) for metallized-ceramic surface-mount components.
To remove solder from a joint, I generally use fluxed braid such as Chemtronics “Soder-Wick.” A hand-held solder pump, such as the Edsyn “Soldapullt,” is occasionally useful for removing large amounts of solder or when removing solder from a hole in a plated-through PC board. Be careful when using either of these approaches that you do not overheat the joint or heat it too long--you’ll melt insulation on wires, or lift the pads from your PC board.
Every now and again you’ll encounter a “stubborn” PC board hole; one on which the braids and pumps just don’t seem to work. Richard Ottosen informs me that in such cases a stainless-steel hypodermic needle may be used to push the solder out! The needle will conduct heat from the iron to the solder, but the solder will not stick to the needle.
You will need a small heat gun for doing shrinkable tubing. Mine is a Master “Mite” with a 650° F (475W) nozzle element.
Here is my list of hand tools for the well-equipped laboratory. It’s a long list, but don’t be dismayed; you are not obligated to buy all of them at once!
Miniature flush-cutting diagonal cutters.
Every one of these cutters is an individual, and it’s tough to find a really good one. If possible, check it out before you buy. The pivot joint should have no out-of-plane play or wiggle, and no light should be visible between the cutting edges when the tool is held up to a lamp. The cutter should be able to cleanly sever a 32 AWG solid wire at any point along its edges, even at the tip.
Mine is a Diamond Copaloy® MS-54G that I have been using for over 20 years. I have yet to find a satisfactory replacement, but I am seriously picky (Update: I have it! It’s an Erem 622N; outlandishly expensive, but the best such tool I have ever seen).
*Never* use your miniature “dikes” for cutting anything but soft copper wire! One application to a piece of hardened steel, and the tool will be ruined forever. I have a cheaper “sacrificial” cutter that I keep handy for questionable applications like cable-ties and steel wire.
Miniature long-nose pliers.
These tools are available with serrated and non-serrated jaws; I have one of each. A miniature long-nose having extra-long jaws, such as the Diamond NN-55, is handy for fishing out dropped hardware in tight spaces.
Miniature round-nose pliers.
These are intended for bending component leads and for forming loops in the ends of solid wire. They look like long-nose pliers with conical jaws; hence the name “round-nose.”
Full-sized diagonal cutters and long-nose pliers.
For use with large, heavy wire. You want quality tools; however, their “fit” is not nearly as critical as with the miniature versions, and so you can buy them right off the shelf. Mine are Sears Craftsman.
I am partial to the Ideal “T-stripper,” no. 45-218 for stranded wires 8-16 AWG and no. 45-216 for wires 16-26 AWG.
Screwdrivers, Phillips and flat.
Mine are Sears Craftsman having a “non-slip” textured finish on the bits. I prefer flat-blade screwdrivers with “cabinet” blades (straight shanks, with no “keystone” flare-out at the bit).
Torx fasteners were apparently first introduced by the automotive industry, as a customer-control tactic. They have since been widely adopted by the electronics industry. They are actually superior to slotted, Phillips, and small Allen fasteners (the heads don’t strip out and mutilate nearly as easily), but you can forget about removing one if you don’t have the proper tool!
Adjustable wrenches (Crescent® or equiv.).
Combination wrenches (box/open end).
“Ignition” wrenches (just a set of tiny combination wrenches).
Ball-end hex wrenches.
Arc-joint pliers (Channellock® or equiv.).
Locking pliers (Vise-Grip® or equiv.).
Insulated terminal crimping tool.
Connector pin extractors.
DIP IC inserter.
DIP IC extractor.
PLCC IC extractor.
I use the Donegan “Opti-Visor.” It is amazing; like having an extra set of high-powered cyborg eyes! As with my custom-made bench, I don’t know how I got along without it for so many years. This item is essential if you are working with surface-mount components.
Component lead bending block (Production Devices PD801 or equiv.).
Trimmer potentiometer “tweak” tool.
Hobby knives and blades.
I have a three-knife set made by X-Acto. The X-Acto #1 knife, with a #11 blade in it, is one of my most frequently used tools and I keep several extras in various places around the house.
Ball-peen hammers of various sizes are useful for a variety of tasks. You should also have a “soft-face” hammer for pounding on things that would chip or mar if struck with a ball-peen; Craftsman makes a hammer with soft plastic on one face and rubber on the other.
Telescoping magnetic “pick-up” tool.
Claw-type pick-up tool.
6-inch dial calipers, calibrated in thousandths of an inch, 0.1 inch per revolution.
12-inch precision rule.
The yard-stick is a highly underrated tool, but you won’t generally use it for measurements. When you drop a part at your bench, it will most likely bounce off of your foot, and then roll under the bench and all the way to the wall. Do you want to crawl under there after it, or would you rather fish it out with the yard-stick? I thought so…
Mechanic’s “feeler” gauges.
Felt-tipped permanent markers.
“Automatic” center punch.
Leather hole punch.
Metal nibbling tool.
You will use your files a lot, even if you have a lathe and a milling machine! I have four sizes each of round, half round, and flat double-cut files for general use, plus a big set of needle files and some single-cut files for finishing operations.
Make sure your files have proper, tight-fitting handles. One slip, while pushing on a file with an exposed tang, could result in an utterly horrible injury.
File card (brush).
Fiberglass “scratch” brush.
This item gets occasional use preparing corroded stranded wires and other surfaces for soldering. Be careful with it; it sheds tiny pieces of glass fiber that can irritate and damage the eyes and skin!
Soft paint brush, 1 inch wide.
This is useful for dusting off small things, removing chips and debris from inside the chassis, etc.
C-clamps, assorted sizes.
Electric drill and bits.
Don’t try to economize on twist drills; get decent high-speed steel bits made by an American, German, or Japanese manufacturer. Anything less could be destructive and dangerous. I once bought some cheap bits from a well-known junk-purveyor (which shall remain nameless, but I will tell you that it has pictures of ships in its advertising logo), and had one shatter in my face! It spoiled my work, too.
Dremel “Moto-Tool” and accessories.
Hacksaw and “bi-metal” blades.
“Bi-metal” hole saws.
Saber saw and “Bi-metal” blades.
Miniature vise (Panavise®or equiv., on a heavy portable base).
Heavy-duty bench vise.
Taps and dies.
I have a Craftsman tap-and-die “set,” and most of its contents have gone completely unused. You’ll probably only need taps for the most common threaded hole sizes (#4-40, 6-32, 8-32, 10-32, 10-24, and ¼-20), and perhaps a ¼-20 die. Get several of the appropriate drill bits for each hole size.
Craftsman makes a nice “screwdriver”-style tap wrench.
Chassis punches such as Greenlee’s, survivors from the vacuum-tube era, are a luxury and they are very expensive. But if you are going to make more than just a few holes of a specific size in thin sheet-metal, you should consider making the investment.
Custom-made special tools.
You’ll often encounter situations where none of your existing tools will do the job, and you will have to make your own. For instance, I once needed a special thin-headed wrench for installing an RF connector in a tight space. I just bought an extra Craftsman open-end wrench of the right size, and then ground it down to the appropriate thickness.
I have a detailed discussion of wire-wrap tools and techniques on the D16/M Minicomputer Page.
I have never used a saber saw that didn’t sound like the End of the World, and a drilling or filing operation is often a veritable carnival of frenzied screeching. Meanwhile, sharp metal chips fly all over the place.
Protect your ears and your eyes; they are irreplaceable!
Another essential item. I have two; a dry-chemical fire extinguisher mounted under my mechanical bench for use in dire emergencies, and a wall-hanging CO2 extinguisher for putting out fires in my electronic gear. I recommend Halon or CO2 types because they leave no harmful residue--the dry-chemical type will destroy your electronics as effectively as the fire!
Unfortunately, Halon and CO2 fire extinguishers are very expensive; my 5-pound CO2 unit cost over $100.
Anti-static bench mat with wrist ground strap.
Everything is CMOS these days. It’s a lot more durable than it was in the old metal-gate era, but still...
Convenience items, and consumables
Shop vacuum cleaner.
2-inch masking tape.
Vinyl electrical tape.
Heat-shrinkable tubing, assorted sizes.
“Hot” glue gun and glue sticks
Slow-curing epoxy cement (Devcon 2-Ton® or equiv.)
Epoxy for general laboratory use. I buy it in big squeeze bottles. Avoid the “toothpaste-tube” or syringe-type packages; they’re a mess.
I don't like the "5-minute" epoxy, because it is brittle and it stinks like a wet dog.
Loctite (formerly Dexter) Epoxi-Patch® cement.
This is a heavy-duty epoxy adhesive for tasks that require some real structural strength. There’s a bonus--this epoxy has very low vapor pressure and is suitable for high-vacuum use.
Cyanoacrylate cement (“super glue”).
This is the nastiest mess ever put into a tube or a jar. I can’t seem to keep the stuff off of my clothes. Yuck!
Anhydrous isopropyl alcohol.
A good, environmentally-friendly solder flux solvent. I apply it with the acid brushes or with a cotton swab. The bristles on the acid brush may be cut down, making it stiffer for scrubbing the solder joint clean.