AMAZON multi-meters discounts AMAZON oscilloscope discounts
<< cont. from part 1
Hand Tools
The range of available hand tools seems practically infinite. Most likely, you'll build up a significant collection of them as the years go by. My own assortment fills several drawers. While nobody needs six pairs of needlenose pliers, there is a core set of tools necessary for disassembling and reassembling the items to be repaired.
Screwdrivers
Today's gadgetry uses a wide range of types and sizes of screws. Some of the screws are incredibly tiny. A set of jeweler's screwdrivers is a necessity. Both Phillips and flatblade screws are used, though Phillips types dominate. More and more, hex and Torx heads are showing up too (see Fgr. 6). The latter shapes started out as a way to prevent consumers from opening their gadgets, but the drivers have gradually become available, defeating that objective. In response, newer types have come along.
One of the most recent is the Trigram, which looks like a center point with three lines radiating out toward the perimeter of the screw head. In time, those drivers will be easier to find as well.
Fgr. 6 Hex and Torx driver tips
Get a good selection of small drivers in all these form factors. At the very least, get Phillips, flat blade and Torx screwdrivers. Pick up a few medium-sized Phillips and flathead drivers too. You'll use the smaller ones much more often than the larger ones, but it pays to have as many sizes as you can find. Really big ones are rarely needed, though.
Cutters
Diagonal cutters, or dikes, are used to clip the excess lead lengths from newly installed components. Most techs also use them to strip insulation off wire. Again, smaller beats bigger. Get a couple of pairs of these things, because they tend to get bad nicks in their cutting edges and gradually become useless. A pair of dikes shouldn't cost more than about $7. Oh, and be sure the handles are insulated. They usually are.
Needlenose Pliers
A pair of needlenose pliers is essential for grabbing things, reaching into cramped spots, and holding parts steady while you solder them. A length of 2 or 3 inches from the fulcrum to the tips is about right. Any shorter and they may not reach where you need them. Any longer and they'll probably be a bit too flexible, reducing their usefulness when twisting is required. Unlike cutters, needlenose pliers rarely wear out or need replacement. Still, get two pairs so you can hold one in each hand and use them at the same time. You'll need to do that now and then.
Hemostats
They're not just for surgeons anymore! Hemostats are much like needlenose pliers, except that they lock, providing a firm grip without your having to keep squeezing the handle. Some have corrugated gripping ends, while others are smooth. Get one pair of each style. These things are indispensable for pulling a component lead from a board while heating the solder joint on the other side. They're great for installing new parts, too. You can find hemostats at most electronics and medical supply houses.
Magnifier
With the size of today's electronics, human eyes have hit their resolution limit for comfortable close-up work. It's essential that you have some magnification. Even if your spot lamp has a magnifying lens, you'll still need a head-worn magnifier, because the lamp will get in your way when it's placed between your face and a small gadget.
Glass is better than plastic, which gets scratched and can even melt when situated very near a soldering iron. Be sure the magnifier you choose can be flipped up out of the way, because sometimes you need to step back a bit from the work and take in a longer view. If you wear glasses, you may need to get a magnifier with adjustable focus to keep it compatible with your eyewear.
Clip Leads
Frequently, testing involves making temporary connections. For that, nothing beats a batch of clip leads, which are wires about a foot long with alligator clips at both ends.
Get at least ten, making sure that the clips are small and have rubber insulating covers.
You can buy the clips and make them yourself, but assembled ones are readily available and inexpensive. Just be aware that the premade ones are usually not soldered; the wires are merely crimped to the clips. After some use, they break inside the insulation, which leads to some head scratching when a connection doesn't produce the expected results. You can never completely trust the integrity of a clip lead. The quick test is to pull the lead taut while holding on to the clips. If broken, one end will fall apart, after which you can solder it on. In time, you'll wind up soldering all of them.
Swabs
Cotton swabs are very useful in the shop. Get the kind with paper sticks, not plastic ones. The paper type can be bent into shapes that will let you poke them into odd corners. If you can find them, also get some chamois swabs. Unlike the cotton type, chamois swabs don't leave little fibers behind. For some uses, especially cleaning video heads on VCRs and camcorders, the fibers can be problematic, and it's even possible to break a video head if the fibers get snagged on it while you clean.
Contact Cleaner Spray
There are many brands of spray, each claiming superiority, but they all do pretty much the same thing: remove oxidation and dirt from electrical contacts. One of the more popular brands is DeoxIT. RadioShack's spray is called TV-Tuner/Control Cleaner & Lubricant. Get a can or two. It's handy stuff and you'll be using it, especially if you work on older gear.
Alcohol
Alcohol can be very useful in cleaning tape paths and heads. Use isopropyl alcohol, and look for the highest percentage you can find. The 70-percent solution sold in drugstores is 30 percent water, which is bad for electronics. Some stores sell 91-percent, which is much better, and I've run across 99-percent on occasion. Don't use ethyl or any other type of alcohol. Be aware that all alcohols can damage some types of plastic rather badly. When working with alcohol, keep it away from plastic casings, LCD screens and control panels.
Naphtha
Sold in little yellow bottles as "cigarette lighter fuel" at grocery stores, and in bigger containers as "VM&P Naphtha" at hardware stores, naphtha is an amazing solvent that will effortlessly remove grime, sticker adhesive, solder rosin, tobacco tar and other general filth from just about any surface. I've never seen it harm plastic, either, not even LCD screens. It's used by dripping a very small amount on a tissue, paper napkin or swab, and then gently rubbing the surface to be cleaned. Naphtha is seriously flammable, so never use it on anything to which power is applied, or near flame or a hot soldering iron. It's best to use gloves, too, to keep it off your skin. Make sure of proper ventilation, because it evaporates quickly and should not be inhaled.
Even if you buy a big can of it, also buy one of the little yellow bottles so you can squirt out tiny doses as needed. It takes very little naphtha to do the job, and you can always refill the bottle from the big can outside your house later on. Keep naphtha containers tightly closed so evaporated fumes won't build up and become hazardous in biological or fire hazard terms.
Heatsink Grease
This silicone-based grease is used between transistors, voltage regulators and other heat-producing parts and their metal heatsinks. It fills in the tiny gaps between imperfect surfaces, helping transfer heat from the part to the heatsink. Even when mica insulators are used, heatsink grease is still required for most parts. (The exception is an installation using a special rubber heat transfer gasket; most of those don’t require grease.) When you replace a heatsinked part, you'll need the grease; omitting it will result in an overheated component that will quickly fail. A small tube of heatsink grease lasts a very long time, as only a thin film is required, and too much grease can actually reduce heat transfer.
Silicone grease is inappropriate for use with microprocessors and graphics chips.
These hot-running parts require special silver-bearing grease, which you can find at computer stores and mail-order suppliers.
Heat-Shrink Tubing
This stuff looks like ordinary plastic tubing, but it has a wonderful trick up its synthetic rubber sleeve: it shrinks in diameter when you heat it up, forming itself around joints and damaged insulation spots in wires. It's much more permanent than electrical tape, which tends to get gooey and let go after awhile. Get some lengths of heat-shrink tubing in various small diameters.
Electrical Tape
Despite its impermanence, electrical tape still has uses in situations where tubing won't fit or can't be slipped over what needs to be insulated. Plus, for extra insulative peace of mind, you can wrap a connection in tape and then put tubing over it.
Small Cups
If you eat yogurt or pudding, start saving the little plastic cups. However you obtain them, those cups are incredibly useful for temporary storage of screws and other small parts as you disassemble machines. Make sure the cups fit into each other. Most will.
Internet (WiFi) Access
Not that long ago, a significant stack of reference guides was required for looking up transistor types, cross-referencing replacement components and finding disassembly hints and diagrams for various products. Now we can do all that and more on the Internet! Some sites charge for schematics, but you can find some free ones. Even if you have to pay a little bit for the diagram, it may be well worth it. There's plenty of free info out there about how to take apart certain products without breaking them, too. Having a computer nearby with Net access is really handy.
Other Handty Tools
Here are some items that can help you get repair work done more easily. You can live without 'em, but you might want to add some to your arsenal as time goes on.
Digital Camera (or Smartphone)
How's your memory? If it's imperfect, like most of ours, a digital camera can save your rear end when you look up from the bench and realize you've removed 35 screws from four layers of a laptop, and you're not sure where they all go. And what's that funny-looking piece over there? The one you took off three days ago, just before you answered the phone and took the dog for his emergency walk? Take pictures as you disassemble your devices. Use the macro lens as necessary to get clear close-up shots; a blurry photo of a circuit board does you little good. Make sure notice which plug went in which connector, and what the shield looked like before you removed it. Experiment a bit with the flash, too, and the angles required to get decent shots without too much glare.
Power Supply
Unless it has its own AC power supply, your repair item runs either on batteries or from an AC adapter. AC adapters themselves fail often enough that you can't assume the adapter isn't the problem. So, running the device under test from a variable power supply can really help. The most important issue when choosing a supply is how much current it can provide. While a little pocket radio might eat around 50 ma (milliamps), a power amplifier or radio transmitter may require hundreds of times as much current. For most work, if you have 5 amps available, you're covered.
There are some fancy laboratory-grade power supplies with digital metering, ultra-precise regulation, and price tags to match. You don't need one. Any decent, hobby-grade supply will do.
Many of the items that demand high current are for use in the automotive environment, so a 12-volt (more typically 13.8 volts, the actual voltage of a car with its engine running) supply with 10 amps or more is great to have as well. That one doesn't need to be variable, since all auto gear runs on the same voltage.
Transistor Tester
Although it's possible to test many characteristics of transistors with a DMM, some failure modes, like excessive reverse leakage (when a small current can flow backward through a defective transistor's junctions), aren't easy to find that way. Dedicated dynamic transistor testers use the transistor under test as part of an oscillator, measuring how the part behaves with real signals applied to it. Under those conditions, you can measure the approximate gain, high-frequency cutoff point and leakage. Many testers can check various transistor types, including MOSFETs (metal-oxide-semiconductor field-effect transistors), junction FETs (field-effect transistors) and standard bipolars.
Basic transistor testers of this type are inexpensive and a great addition to your bench setup. They're fairly easy to make, too, and you can find diagrams in hobbyist magazines.
Capacitance Meter
Capacitors, especially the electrolytic type used in power supplies as filtering elements to smooth the output power, are some of the most trouble-prone components of all. In addition to suffering complete failures like opens and shorts, capacitors can gradually lose their ability to store energy. Worse, their internal equivalent series resistance (ESR) can rise, in which case the capacitor will measure just peachy keen on a meter, but will act like it has a big resistor between it and the circuit when it's in use. Excessive capacitor ESR is one of the most common causes of oddball circuit behaviors.
AMAZON multi-meters discounts AMAZON oscilloscope discountsSome DMMs have built-in capacitance measurement, but ESR meters are still on the expensive side. You can get by without one, though; in Section 11 we're going to explore how to evaluate capacitors in operating circuits, using our good friend the oscilloscope.
Signal Generator
More useful for servicing analog equipment than digital, a signal generator lets you inject a test signal into a device's signal-processing stages to see whether doing so causes the expected effect. With today's digital devices, it's not something you'll use very often, but it has some application in simulating the clock oscillators that drive digital circuitry. Many products, like MP3 players, have both analog and digital sections, and a signal generator can come in handy with those if the audio circuitry malfunctions.
The generators are called function generators when they have the ability to create different kinds of waveforms, such as sine, triangle and square waves. While sine wave-only generators are usually segregated by frequency band, either audio or radio, function generators may have a wide range encompassing both, though they don't offer high-frequency ranges anywhere near those of radio-only generators.
Many function generators operate from a couple of Hz (hertz, or cycles per second) to around 2 MHz (megahertz, or millions of cycles per second), while radio-frequency (RF) generators may reach hundreds of megahertz.
Frequency Counter
A frequency counter does just that: count the frequency of a signal. It does so by opening a gate for a precise period of time and counting how many cycles of the signal get through before the gate closes again. A counter is most useful when the frequency of a circuit's oscillator needs to be adjusted accurately. This is rarely the case with digital devices like cameras and computers, but it can be critical when calibrating the master oscillators that control the tuning of radio receivers and transmitters.
If you're considering getting a counter, look more at its low-frequency capabilities than at the high end, unless you plan to work on UHF or microwave systems. Many of the inexpensive counters that can hit 1 GHz (gigahertz, or billions of cycles per second) are optimized for radio work and have gate times too short to count audio frequencies accurately. (The slower the signal frequency to be counted, the longer the gate has to stay open to let enough cycles through for a proper count.) Oh, and counters are another product category, like DMMs, that may display lots of meaningless digits.
Especially with the cheapies, there can be a long string of numbers to be taken with a significant grain of sodium chloride.
Frequency counters are capable of counting regular, continuous signals only; they're useless with complex, changing ones. To extract frequency information from those, you need…yup, a scope. See, I told you that darned scope was your friend! Speaking of scopes, you'll need an extra scope probe for your counter unless you want to share one with the scope. Get one with a 10X/1X switch, as that is especially handy for counter use.
Analog Meter
The moving meter needle of an old-fashioned analog VOM offers some info to the trained eye that a modern DMM can't. Slowly fluctuating voltages, which you might encounter with, perhaps, a bad voltage regulator or a circuit pulling too much current, are even easier to see with a VOM than with an oscilloscope. Little voltage dips or spikes cause a characteristic bounce of the needle that's very informative, too. You can even get a rough estimation of an electrolytic capacitor's condition with an analog ohmmeter by watching the needle quickly rise and then slowly drop. With a DMM, such changes are just rapidly flashing numbers impossible to interpret.
A special type of VOM is known as a VTVM, for vacuum tube volt meter. A VTVM works like a VOM, but it contains an amplifier, making it considerably more sensitive to small signals and much less likely to steal meaningful amounts of current from the circuit under test, or load it down. VTVMs go back a long way, from before there were transistors, and early ones really did use vacuum tubes. Later models substituted the tubes with a very sensitive type of transistor called a field effect transistor (FET). Those were known as FET-VOMs, but most people continue to call any amplified analog meter a VTVM, whether it has a tube or not. If you can find a FET-VOM, you might want to snap it up, because they're getting rare. True VTVMs are very, very old, and replacements for those small tubes are hard to find, but some working ones are still out there.
Decent VOMs, FET-VOMs and VTVMs occasionally turn up at hamfests. As long as it works, an old VOM is as good as a new one; there's not much in it to go wrong.
If the meter needle moves without getting stuck and the selector switch works, you should be good to go. True VTVMs may run on AC power or on batteries, but the battery-operated units require cells nobody makes anymore, so avoid those meters.
VOMs and FET-VOMs use batteries that may sit in them for years, so check inside the battery compartment to make sure an old cell hasn't leaked and corroded the contacts.
Amplified meters (VTVMs and FET-VOMs) have a lot more in them than do VOMs, too, so it's best to test their functions before buying.
Many companies have made VOMs, but the best oldies were made by Simpson, which also made the best VTVMs. Some of those ancient Simpsons still go for real money, and they're worth it. You pretty much have to shoot them when you don't want them anymore. Triplett was another company that made great meters.
Isolation Transformer
It used to be that most AC-powered gear had a linear power supply, which shifted the incoming voltage down to a lower one through a transformer operating at the 60-Hz line frequency. The transformer, an assembly of two or more coils of wire on an iron core, had no electrical connection between its input and output; the energy was transferred magnetically. This arrangement helped with safety, because it meant that the circuitry you might touch was not directly connected to the house wiring, and thus couldn't find a path to ground through that most delicate of all resistors, you.
Unfortunately, to move a lot of power required a big, heavy transformer.
Today's switching power supplies, or switchers (see Section 14), chop the incoming power into fast bursts to push lots of energy through a small, light transformer. They're much more dangerous to work on, because some of their circuitry is connected directly to the AC line, and it may have several hundred volts on it-and often it's the section that needs repair.
An isolation transformer is just a big, old-style AC line transformer into which you can plug your device. The transformer has a 1:1 voltage ratio, so it doesn't change the power in any way, but it isolates it from the AC line, making service of switchers a lot safer. If you're going to work on switching power supplies while they're connected to the AC line, you must have an isolation transformer. Many times, you can fix switchers while they're unpowered, so having an iso-transformer is optional. Just don't ever consider working on a live switcher without one. Seriously! You don't want the power supply to wind up being the only thing in the room that's live, if ya know what I'm saying.
Magnifier (Mantis):
USB Microscope:
Stereo Microscope
With electronics getting smaller and smaller, even a head-worn magnifier may not be enough for a comfortable view. More and more, techs are using stereo (two-eye) microscopes to get a good, close look at solder pads on grain-of-salt-sized components.
When you choose a microscope, get one with low magnification power. You're not trying to see bacteria on the parts! 10X to 20X should be more than enough. Anything higher and you probably won't even be able to recognize the component. A mono (one-eye) microscope can be used, but having the depth perception that comes with stereo vision can really help, especially if you're trying to solder or desolder under the microscope. To find a microscope, check eBay. Sometimes they go for surprisingly affordable prices.
Video-camera microscopes using a computer for display are becoming available, often for less than traditional optical microscopes. If you have room for a laptop on the bench, they're worth considering.
Bench Vise
Wouldn't it be wonderful to be gifted with three hands? If you have only the standard two, you may find it difficult to hold a circuit board while pulling a component lead from one side and heating the solder pad on the other. Check out the PanaVise and similar small vises designed for electronics work. Some offer attachable arms perfect for gripping the edges of circuit boards, and they let you swivel the board to whatever angle you need.
Hot-Melt Glue Gun
A small glue gun can help you repair broken cabinet parts, and a dab of hot-melt glue is also great for holding wires down. Manufacturers sometimes use it for that, and you may have to remove the glue globs to do your work. Afterward, you'll want to replace the missing globs.
Magnet on a Stick
The first time you drop a tiny screw deep into a repair project and it won't shake out, you'll be glad you bought this tool. It's useful for pulling loosened screws out of recessed holes, too. Get one that telescopes open like a rod antenna. Just keep the darned tip away from hard drives, tape heads, video head drums and anything else that could be affected by a strong magnetic field. Also, keep in mind that the metal rod could contact voltage, so never use the tool with power applied, not even if the device is turned off. Charged electrolytic capacitors can impart a jolt after power is disconnected, so keep away from their terminals too. See Sections 3 and 7 for more about capacitors.
Cyanoacrylate Glue ("Super glue")
Also known by the trademarks Super Glue and Krazy Glue, instant adhesive can be useful on some plastic parts. It's strong, but it has poor shear strength and is not terribly permanent, so it shouldn't be used for repair of mechanical parts that bear stress, as the repair won’t last long. This type of glue is handy for holding things together while you fasten them with other, more permanent means. Just be aware that it outgases a white film as it hardens that is tough to remove, so keep it away from lenses, display screens and other surfaces where that might be a problem.
Component Cooler Spray
This stuff is colder than a witch's, um, iced tea, and it's used to put the deep freeze on suspected intermittent components, especially semiconductors (diodes, transistors and IC chips). While it might seem primitive to blast parts instead of scoping their signals, doing so can save you hours of fruitless poking around when circuits wig out only after they warm up. One good spritz will drop the component's temperature by 50 degrees or more and can reveal a thermal intermittent instantly, returning the circuit to proper operation for a few moments until it heats up again.
Data Books
Although the Internet offers lots of great service-related information, some important tidbits are still more easily found in a good old data book. Transistor cross-reference data, which you use when you need to substitute one transistor type for another because you can't get the original type, is most easily looked up in a guide. So is pinout data for various ICs, voltage regulators and varieties of transistors.
Motorola, National Semiconductor and ECG used to give away reference books, but these days you'll probably have to buy them from electronics supply houses.
At the least, consider getting a transistor substitution guide. Of course, if it's offered as a CD-ROM or a downloadable PDF file, that's even better, assuming you have a computer near your bench.
Parts Assortment
Having a supply of commonly used components is quite handy. You can strip old boards for parts, but it's time-consuming, and you wind up with very short leads that may be difficult to solder to another board. Plus, your stash will be hit-or miss, with big gaps in parts values. Consider buying prepackaged assortments of small resistors and capacitors or going to a hamfest and stocking up for much less money. There, you're likely to find big bags of caps, transistors, chips, resistors, and so on, for pennies on the dollar. Avoid buying transistors and chips with oddball part numbers you don't recognize, because they may be house numbers, which are internal numbering schemes used by equipment manufacturers. Those numbers are proprietary, and there's no way to determine what the original type number was.
Thus, you can't look up the parts' characteristics, making them useless for repair work. Resistors and capacitors, luckily, almost always have standardized markings, and you can easily measure them if you have the appropriate meters.
Don't bother buying ceramic disc capacitors, because they almost never go bad, so you aren't likely to need any. If you do run into a suspicious one, you can pull its replacement off a scrap circuit board. Instead, focus on resistors, transistors, voltage regulators, fuses and, especially, electrolytic capacitors.
Electrolytic capacitors are the cylindrical ones with plastic sleeves around them and markings like "10µf 25VDC." There are many varieties of 'lytics, but some are pretty common, and substitution of similar but not identical parts is feasible in many instances. (We'll explore how to do it in Section 12.) Get an assortment of caps in the range of 1 to 1000 µf (microfarads), with voltage ratings of 35 volts or more. The higher the ratings, both capacitive and voltage, the larger the cap. While it's fine to replace a cap with one of a higher voltage rating, get some rated at lower voltages too, in case there isn't room on the board for the bigger part.
Stocking up on transistors is tricky because there are thousands of types. Small signal transistors, which don't handle a lot of current, are not hard to substitute, but power transistors, used in output stages of audio amplifiers and other high-current circuits, present many challenges, and they're usually the ones that need replacement.
Still, small transistors are very cheap-in the range of 5 to 25 cents each-and it's worth having some around. Get some 2N2222A or equivalent, along with some 2N3906. You may find hamfest bags of parts with similar numbers that start with MPS or other headers. If the number portion is 3906 or 2222, it's pretty much the same part and will do fine.
Diodes and rectifiers are frequent repair issues, so it pays to have some on hand.
The only difference between a diode and a rectifier is how much power it handles.
Small-signal parts are called diodes, and larger ones made for use in power supply applications are dubbed rectifiers. Look for 1N4148 and 1N914 for the small fry, and 1N4001 through 1N4004 for the big guns.
The bridge rectifier, which integrates four rectifiers connected in a diamond configuration into one plastic block with four leads, is commonly used in power supplies. It's a power-handling part that fails fairly often. Get a few with current ratings in the 1- to 5-amp range and voltage ratings of 150 to 400 volts.
To house components, most of us use those metal cabinets with the little plastic drawers sold at hardware stores. Sort resistors and capacitors by value. If you have too many values for the number of compartments in the drawers, arrange the parts into ranges. For example, one compartment can hold resistors from 0 to 1 K-Ohm (kilohm, or thousand ohms), while the next might contain those from just above 1 K? to 10 K-Ohm. Once you learn to read the color code (see Section 7), plucking the part you need from its drawermates is easy.
Scrap Boards for Parts
Despite what I said about stripping old boards, you do want to collect carcasses for parts. No matter how large your components inventory is, the one you need is always the one you ain't got! An old VCR or radio can provide a wealth of goodies, some of which are not easily obtained at parts houses, especially at 11:30 p.m. on a Sunday, when your hours of devoted sleuthing have finally unearthed the problem-at least you think so-and you would sell parts of your anatomy for that one darned transistor, just to see if it really brings your patient back to life.
If you have room, it's easy to pile up dead gadgetry until your spouse, conscience or neighbors intervene. You're highly unlikely ever to need cabinet parts, because they won't fit anything beyond the models for which they were made, so saving entire machines is somewhat pointless and inefficient. The better approach is to remove circuit boards, knobs and anything else that looks useful, and scrap the rest. Don't bother stripping the boards; just desolder and pull off a part when you need it. If the leads are too short, solder on longer ones.
Wish List
For most service work, you can easily live without the following items, but they make for good drooling. Some advanced servicing requires them, but not often.
Inductance Meter
This meter reads the inductance value of coils, which seems like something quite useful, right? It's really rare, though, for a coil to change its inductance without failing altogether. Usually, the coil will open (cease being connected from end to end) from a melted spot in the wire, as a result of too much current overheating the windings.
In the high-voltage coils used in CRT TVs and LCD backlighting circuits, insulation between coil windings can break down and arc over, causing a short between a few windings but leaving most of them intact. That will change the coil's inductance, making an inductance meter useful. To get any benefit from it however, you need to know what the correct inductance should be, and often there's no way to ascertain that unless you have a known good coil with which to compare the suspect one. That, and the fact that coils don't wear out and show gradually declining performance the way electrolytic capacitors do, accounts for the inductance meter being on the wish list, while the capacitance meter is a little higher up the chain of desire.
Logic Analyzer
An offshoot of the oscilloscope, a logic analyzer has lots of input channels but shows only whether signals are on or off. It’s used to observe the timing relationships among multiple digital signal lines. Getting benefit from it requires knowledge of what those relationships should be, information rarely provided in the service manuals of consumer electronics devices. It’s unlikely you'll ever need one of these.
SMT Rework Station
Surface-mount technology, known as SMT, or sometimes SMD (surface-mount device), is today's dominant style of componentry, because it makes for much smaller products and also eliminates the need for drilling hundreds of very precise holes in the circuit board. SMT stuff is somewhat hard to work on, thanks to the size scale and the lack of holes to secure a part while you solder it. The pros use SMT rework stations, which are fancy soldering/desoldering stations with custom tips that fit various kinds of chips.
SMT rework stations are expensive and not hobbyist material, at least so far.
Spectrum Analyzer
This is a special type of scope. Instead of plotting voltage versus time, a spec-an plots voltage versus frequency, letting you see how a signal occupies various parts of the frequency spectrum. Used extensively in design and testing of radio transmitters, spec-ans are expensive overkill for most service work, unless RF is your thing. Ham radio operators covet these costly instruments, but you won't need one to fix normal consumer electronics devices. Besides, it’s illegal to service transmitters in any way that could modify their spectral output unless you're a licensed amateur radio operator working on ham gear or you hold a radiotelephone license authorizing you to work on such things.