From my experience, I use my HV probe maybe once or twice a year. I still consider it a crucial piece of test equipment.
Conversely, I use my scopes, logic probe and digital voltmeters all the time. Same with my soldering iron (and soldapult). LOL - and my microscope!! I really luv my microscope.
If you watch repair vids, especially Brian's, you'll realize how important a Fluke 9010A is. Similarly, I like my CATBOX. And sometimes I use a signature analyzer. My NEOLOCH Inquisitor is great for testing ICs, as are my ABI digi and analog IC testers.
The HP comparator is OK. Lots of test-bench power supplies. I also have electronic load for testing ARII and other power source etc. Gotta have SuperGun too.
What's my point? You can't cheap out on good test equipment, and seemingly, you cannot have enough test equipment.
Conversely, I have a Fluke 9010 and never use it. I do most of my PCB repairs with a $20 logic probe w audio, and occasionally my HP signature analyzer. I do most troubleshooting on the bench, just powering the game logic with +5V, then test the rest of the functions in the cabs I have (using the scope on occasion to track down analog vector section issues).
I do use my HV probe frequently, but I do a lot of monitor work. And I use it with a cheapo $20 DMM that works just as well as the two Flukes I have, as I compared it. I like having many cheap DMM's strewn about, and dedicate them to specific purposes/places in my setups, so I always have one handy and don't have to go looking for one. Also, DMM's often have little quirks and features that differ between meters, and some things are nicer in certain situations (e.g., and on/off button vs the twist-to-power-on selector switch, or a backlight, or beep features, etc). I have yet to find one DMM that has everything I personally like, but I like having many of them anyway, so I get the best of both.
I don't use a chip tester, but I have an Asteroids PCB that is heavily socketed, which I will use to confirm bad chips on occassion, though I rarely do that, as I can verify they are bad using the board I'm repairing most of the time (e.g., if you replace a chip and it doesn't change the behavior of the board in a way that you can observe with your logic probe or eyes, it was most likely not bad.)
So to the converse point, equipment is never a substitute for experience and technique. My path has always been to have just less than the equipment you need (and work your way up to it, knowing that you really need it), rather than spend tons of money up front on stuff you won't need or use. You'll develop better debugging skills and a better intuitive knowledge of the boards you're repairing if you start with simpler tools, IMO.
Note that VC's and my opinions are more the two ends of a spectrum. Your truth likely lies somewhere inbetween.
Well said by by two pillars of the community, and I agree - with both! I am in that middle ground.
A good, reliable DMM is a must for verifying voltages, resistance, capacitance, and continuity. Some can do even more. It may be the most important tool to spend a little more on to get one that you know you can trust.
I use my trusty Elenco LP-560 logic probe a lot, and in fact at $20 I bought two since it is sometimes helpful to probe two pins at once - for example to see if an output and its inverted output are actually inverted. But not often. For that I'd turn to my scope that includes a logic analyzer, or the HP comparator. The comparator is limited to 16 pin devices, although there is a 20-channel version and cards. Even that cannot do tri-state devices like buffers, so it has its limitations. There are devices to test a chip without removing it but they get pricey and are hard to come by.
I have a Fluke 9010A and use it quite a bit to verify RAM and ROM in situ. I have written scripts for various boards that make use of the 9010 probe to test address decoders and other parts of the board. I enjoy writing the scripts and there is a fair amount of documentation about that and the unit in general. That said, I'm not sure if I could bite the financial bullet to acquire the mainframe and pods at current prices. Luckily I got mine years ago.
Same goes for a signature analyzer. It is good for times when there is no clear starting point to troubleshoot a circuit that feeds back onto itself. For example, if the RAM and ROM and CPU and clock are all good, but a program still refuses to run and there are no stuck pins (or maybe they are stuck because it's not running yet) using signatures can help locate the fault. But that only works on boards for which there are documented signatures.
Sometimes the best you can do is narrow down the suspects, by using an understanding of how the chips and different sections of the PCB are supposed to operate and interact. It's a mix of past repair experience, deductive reasoning based on observed behavior and reactions, chips that seem to fail more than others, as well as research of other people's repair logs. It's also a mix of how much time and effort you want to invest to learn about repair technique and that particular board versus just getting it fixed by brute force replacement ('shotgun').
If you are going to remove a chip, a good desoldering station is important. It is possible to use a solder sucker and/or braid, but it is harder and takes longer, and does more damage to the board. It may seem extravagant to spend a few hundred... until you use one. Once a chip is removed it is much easier to test. My TopMax EPROM programmer can also test a range of chips, while Andy's method of putting a chip in a socket of a known-good board is real-world verification at its best.
I have gone through a few scopes, and currently use a Tek 2247A for analog purposes and recently splurged on a Rigol MSO2202A digital scope with logic analyzer. The first ones were cheaper, older scopes that served their purpose (provide information without too much capital investment) but as I learned more and was able to make use of more features, I could justify paying for a better scope. The ones I have now have more features, are newer and more reliable, but more expensive. One piece of advice for the current range digital scopes is to consider not only features and price, but also the user interface and manufacturer support. The interweb will have reviews that address those topics.
An HV probe is not too expensive. If you only need on occasionally perhaps you can borrow one. If you are doing more of your own monitor work or have a growing number of games, then the expense becomes easier to justify.