Test equipment: how much is needed?

[Skywave]

A topic for general discussion.

In one of M.G. Scroggie's books, he makes the remark that it is better to have a few items of test equipment that the user is familiar with, knows its abilities and limitations, where and when it can be used and how and when it can't, etc., as opposed to having a plethora of items, many of which will be rarely used, and when they are employed, the user will often have to refresh his memory as to how & where to use it, etc. - which can lead to inconvenience, mistakes, etc.

I have good deal of respect for M.G.S.'s thinking on many such philosophical ideas: the above was written in the 1950's. However, compared to when the above was written, today, there is a much greater range of electronic devices and technologies that most of use or encounter. So, is M.G.S.'s comment still applicable today? Is it only partly applicable? etc., etc. . . .

Al.

For just one instrument, given today's inexpensive equipment, a digital (yes digital, one with an FFT function) 'scope and a few resistors (for current measurement). Learn how to drive that and almost all parameters can be measured. And then a signal generator, I got a Siglent one that can do almost anything https://www.tester.co.uk/siglent-sdg...Fawp0wod-IkFvA


Of course a multimeter is good to have too just for the convenience.

[ColinTheAmpMan1]

I know the old adage that a (wo)man with one multimeter knows what voltage or current (s)he is looking at, but one with two is never too sure....But what do you do when that one piece of test-gear fails? Buy another and bin the first, or buy another and set about repairing the first? I think I know what most members of this Forum would do. (Hint: the second option).
Colin.

[MrBungle]

Honestly of all the things I've fixed over the last 20 years or so, my most useful tool has always been the humble digital multimeter. In my case, my first choice is a Fluke 8024B that I paid about £9 for which was in a right state. Rarely a day goes by where at some point I don't use this. I could probably get by with just that if I had to.

Now there is a big divide between fixing things and building them from scratch. You need a lot more equipment to do that effectively. Add a bench power supply, scope, frequency counter, function generator, RF generator, power meter and a couple more DMMs and an analogue meter and you're getting closer.

Really I did consider a while back getting rid of everything and building all my test gear from scratch. My father did this back in the 1960s/70s because he couldn't afford to buy any. He ended up with what he needed to do a job, not what was convenient at the time and learned a lot more than I did buying it.

As for the original point, I write (and fix) software during the day. We use tools far more complicated than any piece of test equipment and I don't seem to forget how to use them on a regular basis even if I don't touch them for months.

[paulsherwin]

We get threads like this on a regular basis, and they all cover similar ground. All you need to work on old radios is a cheap soldering iron and a cheap DMM. Everything else is down to personal preference, available finance and the sort of equipment being worked on.

[Bazz4CQJ]

Originally Posted by paulsherwin

We get threads like this on a regular basis, and they all cover similar ground. All you need to work on old radios is a cheap soldering iron and a cheap DMM. Everything else is down to personal preference, available finance and the sort of equipment being worked on.

Exactly - and the guys who are professionally involved in radio and electronics feel unhappy if they don't have much the same kit at home as they do at work.

B

[Radio Wrangler]

A soldering iron, a basic multimeter, a selection of spares and either a fair amount of knowledge or else a guide with that knowledge.

But when it comes to acquiring that knowledge a bit more test equipment can allow the learner to better see what's going on. It's a fine balance. The aim is to help the beginner, not to scare him off with a flight deck of spectrum and network analysers.
A basic scope and sig gen are good teaching tools. They might not be necessary, but they can help people visualise what is going on.

After that, it's a free world and you're free to collect whatever you wish. I wouldn't be bothered about an Oceanic Surcouf, or a mirror-lid TV. An HRO or an AR88 is more up my street, and I dug deep into my pockets for my HP 8566B. If we were all interested in just the same things, imagine what the queues and the prices would be like!

David

[The Philpott]

As for having instruments of different specs. and operating criteria, I can't argue with the assertion this might be inconvenient or lead to mistakes, but personally this is something i use to keep my brain agile.

On the other side of the coin it makes you into a 'double-checking Thaddeus' ( A Lee & Herring sketch reference there, ) and one hopes this actually helps to AVOID mistakes.

I do the same with other tech. including motor vehicles, if i get the chance to use something unorthodox i take it.

[TonyDuell]

To me it all comes down to my method of fault-finding (which has never let me down) :

You read the service manual and circuit diagram and work out what the device (say a radio) should be doing. In other words, you would deduce that you would find a signal on 'this grid of the mixer' at, say, 1.2MHz from the local oscillator. An Amplitude modulated 465kHz signal on the anode of the IF amplifer. Audio on the top of the volumer control. 300V DC on the HT+ line. And so on.

And then you look at the device and see what it is actually doing. As it's not working properly presumably there are differences between what it is doing and what it should be doing.

You then deduce what fault could cause those differences. Do more checks to home in on the fault.

You can't see electricity. You can't look at a radio (or whatever) and see what is going on in the circuit. So you need test gear to be able to see what is actually going on.

What test gear you need depends on what you are working on and what the fault is. For me (as for most of us I think), top of the list is a multimeter. It does not have to be particularly accurate for most work. Very few radios will work with a 300V HT+ line and do nothing with a 290V or 310V HT+ line. You just need to know if the HT+ line is present and not too far off what it should be.

Second on the list _for me_ is a logic analyser. This is something that has no use whatsover on most radios (and certainly not vintage radios) but as I mention in my profile, my main interest is vintage computers. You cannot hope to repair a bit-serial processor like the one in an HP9800 machine without a logic analyser. You just can't see what it is doing.

Next come the 'scope and a bench power supply. The last is very useful for checking for silly faults in lamps, motors, etc.

For what I do I don't need a signal generator or spectrum analyser much. If I did more work on radio stuff I would.

Perhaps I'd better not add that I collect obscure test gear (the odder the better) and even use it sometimes. My workshop contains various telephone testers, tegraphic test signal generators and distortion measuring sets, wow and flutter meter, audio distortion analyser, datacomms testers, etc. And that's just the ones I can see without getting up...

[HamishBoxer]

Maybe not quite test gear but an isolation transformer is worth while. Other than that all I really use is my Fluke multimeter, although on modern power supplies I do have an ESR meter.

I do have a large selection of stuff but there again I just love test equipment!

[mole42uk]

I spent many years using only an oscilloscope. Although today my workshop groans with test equipment, not only do I not know how to use some of it but I still work with a 'scope probe to hand.

[AC/HL]

Probably applies to many of us, you can't argue with honesty. Meter in my case (if I can find it)

[paulsherwin]

There's nothing wrong with scopes, and they can be very helpful. Most people learn to use a scope in a professional or training context though, and they can be very daunting for a beginner. We often get beginners signing up here assuming that they need one. Mine lives in the cupboard under the stairs and I rarely get it out.

I mostly use:

Blackstar bench DMM
Cheap Chinese component analyser
Dirt cheap market stall DMM
Avo 8
1960s Japanese Eagle transistor tester (for Ge types)

I'm just a bodger though

[Skywave]

Originally Posted by paulsherwin

We get threads like this on a regular basis and they all cover similar ground. All you need to work on old radios is a cheap soldering iron and a cheap DMM.

"Working on old radios" and the minimum kit required for that purpose: yes, agreed √. However, I did not limit this thread topic to such a narrow range and I am pleased to see comprehensive replies which recognise that.
To me, the degree to which MGS's remarks are relevant (or not relevant) today is simply a metric as to how far electrical / electronic technology has advanced in the intervening years. Everyone will have his / her own 'take' on that.

Al.

[evingar]

I used an analogue DMM for all my tinkering prior to starting work in 1981, and yes, you can use it to fix most valve equipment, even complex stuff like tellys.

However, once I got to use a 'scope (in my case Tek 465) at work, I very quickly invested in one for home use. An analogue 'scope (now a Tek 2464) is my "reach for first" instrument and gets used a lot more than my DMM for "live" fault finding. Obviously on live chassis stuff I use it in association with an isolating transformer.

The cost of good 2nd hand analogue 'scopes has now fallen to the level that even occasional tinkers can afford them. My personal "minimalist" equipment list would be :-

1. Isolating transformer (for live chassis work)
2. DMM
2. Scope
3. Signal generator

[Skywave]

Originally Posted by paulsherwin

There's nothing wrong with 'scopes and they can be very helpful. Most people learn to use a 'scope in a professional or training context though and they can be very daunting for a beginner.

IMHO, test equipment like a 'scope - even a very basic one - are most likely to be daunting to a beginner if he / she has not done the necessary studying of basic theory first. In that regard, it could - repeat could - be argued that forums such as this (as wonderful as they are) actually do not help such beginners, since such beginners are thus tempted to jump straight in feet first without having acquired the essential elementary comprehension first. That is my personal opinion only, based on my experience: it is not intended to be taken as prescriptive; each member will have his/her own opinion on such a matter, and quite rightly too.

Al.

[G0HZU_JMR]

For those that do have 'lots' of test gear, I would suggest that it's usually a bad idea to try and cram it all into the work area in one go. It's rarely 'needed' all of the time. I see a lot of benches on the internet where the operator's needs come second to the test gear, the tools and the component drawers. It is as if these items own the vast majority of the work area 24/7. Often the space left for the operator is tiny. Barely enough room for the device under test/repair a multimeter and a cup of tea!

I have a lot of RF test gear here but I try and store most of it away in a large cupboard and only take it out when needed. Also, I don't store tools or parts on my workbench. This keeps my main workbench (and two work desks) in a reasonably uncluttered state with lots of space to move stuff around. Sadly the main bench space still fills up with cables and various small items so I do have to clean it up fairly regularly.

30 years or so ago, any budding radio ham who wanted to do some home construction or repairs would look to buy the classic threesome of a scope, a counter and a sig gen. This assumes that they already had some form of multi meter and a basic power/SWR meter. Stuff like audio generators, dummy loads and couplers could be homebrew. Add to this a basic RF probe and maybe a signal injector and you could do most things in a typical service manual for a ham/CB radio.

When I was a student I was trained to do diagnostic work with just an AVO 8 and a home made diode based RF probe. Sometimes I was allowed to use a signal injector as well

[Skywave]

Originally Posted by evingar

I used an analogue DMM for all my tinkering prior to starting work in 1981 and yes, you can use it to fix most valve equipment, even complex stuff like tellys.

Fixing T.V.s: agreed. Many years ago when I was employed part-time in the T.V./ Radio/Audio fixing business, the 'shop always had a 'scope on the shelf above the bench. However, the boss or I used it only very rarely. An AVO 8, an isol. transformer and a T.V. pattern generator were the usual 'fixing tools' (in the category of test equipment).

Al.

[Skywave]

Originally Posted by paulsherwin

I'm just a bodger though

You do yourself an injustice! From your posts that I have read here over many years, you are far from being a bodger, Paul!

Al.

[G0HZU_JMR]

In one of M.G. Scroggie's books, he makes the remark that it is better to have a few items of test equipment that the user is familiar with, knows its abilities and limitations, where and when it can be used and how and when it can't, etc.,

One thing that has not changed, is the need for the operator to always ask themselves: "Am I making a valid measurement?"

Even with today's exotic test gear it is possible to adopt poor practice/preparation and make poor measurements. I always ask myself if I've taken into account all possible contributors to overall measurement uncertainty. So I agree that you really do need to understand the limitations of your test gear and any test procedures that use that piece of test gear. This knowledge can only come from training and experience