Recommendations for a cheap 'scope

[Bonky28]

Thanks everyone. The consensus seems to be that I should be able to mend my Hacker without the aid of a 'scope but that having one MAY be useful in other operations and would teach me a lot about electronics.. I'll try the Hacker again this week but will be on the look-out for a cheapie 'scope. I now have some names and models to research.
Thanks again,
Richard

[Radio Wrangler]

There is a wide spectrum of opinions.

At one end there are guys from high tech backgrounds who wouldn't think of repairing a basic radio unless they have gear which once cost a significant fraction of a megabuck warmed up and ready to roll. With my past I err to this side.

At the opposite end there are guys who can fix basic radios with no test-gear. A basic meter is more than enough, bordering on luxury.

Both extremes have some valid points, and they also have some blindspots. Sanity lies somewhere between these extremes. You get to pin the tail on the donkey and decide just where you think a sensible compromise lies.

To be able to fix things quickly, with minimal test gear, some people have built up a high level of skill. They got this through a lot of experience. If you mess about with things and fix them, you can't avoid learning along the way. It just takes time.

What has changed is that tons (literally) of once unreachably expensive test equipment now turns up for prices within reach of hobbyists... Things repair shops and small firms could never afford. Now, some of this gear can show things more clearly and make learning processes simpler, easier and quicker. Some of this gear can lead you off down a path of forever fixing test gear. It can feel like those guys on old variety shows spinning lots of plates on sticks, always running to keep everything going.

Sensible compromise is the key. If a bit of equipment will be a net help and not a hinderance, and it's affordable, go for it. Other people did without it, but they didn't get the same mix of opportunities that are around today. They had other opportunities that aren't around any longer. (If you could sell time-machine trips to Tottenham Court Road, or Shude Hill)

Don't get sucked nto test equipment collecting unless you want to take it up as a hobby.

Remember that wonderful instruments help, but they still don't do the work for you. You have to interpret what they show and think.

"He fixes radios by thinking!" was a phrase applied to Richard Feynman, and look where it got him.

David

[mhennessy]

Hand on heart, I wouldn't attempt to repair a Hacker without a 'scope. I'm not even sure I could. And having read this thread, I can't agree that there is a consensus to not get a 'scope. Given that suitable models can be found for less than £50 - often free - it seems pointlessly masochistic to think you can manage without.

People have different backgrounds, and some of them are able to get by without one. "Get by" is the key part of that sentence IMHO. Those that do have years of hard-won experience with no 'scope, from the days when 'scopes were very expensive and not all workshops could afford one. You don't have that experience; you're starting now. You don't have to suffer the indignity of not having a 'scope. Not having a 'scope will make it much harder to understand and learn.

I've told this story many times before, so the short version: about 25 years back I worked in a repair shop with an older engineer from the no-scope era. The pristine 60MHz Hameg sat under a dust sheet, and only came out when it absolutely had to. I was impressed at how he got by without it, but seriously frustrated to see just how much his "no-scope" policy slowed him down. At that time, I had a 'scope at home - it wasn't fully working, but I still used it as much as I possibly could. It kept the shed warm

[MrBungle]

Case in point with the price, I just snapped up a 200MHz Tektronix 475 this morning with DM44 module for £30. Need some repairs but should do for when I hit the BW limit on my Rigol.

[cmjones01]

Originally Posted by Argus25

They probably are in a very precarious position by now with the Dallas DS1225 NVram batteries nearly exhausted.

Indeed - I have a 2465A which might suffer from this (I've never looked inside, though) and a 2430A which is already doing so (the waveform memory battery is already dead, which I don't care about, and the calibration procedure when the calibration memory battery dies isn't onerous. I should sort it out though). However, the original 2465s use an obscure EAROM rather than NVRAM. The EAROM which doesn't have a battery. Of course, they can still fail, but they don't have the same ticking-time-bomb aspect as the Dallas modules.

The one I'm really worried about is my CSA803A which seems to have lots of those Dallas modules in. I'm pretty sure it's all self-calibrating, though, and it's 15 years younger than the 24xx scopes!

Chris

[MrBungle]

You can still get the Dallas modules and you can actually, with some surgery, fix them if they do snuff it. I've done one in a SPARCstation a number of years ago as per the instructions here:

https://gigawa.lt/gigawa.lt/Sun_NVRAM.html

If you do this, make sure you stick the batteries in a ziplock or something. Typically the thing that killed it in the end wasn't the Dallas chip dying, it was the batteries I'd attached leaking.

[KeithsTV]

I use a scope for servicing equipment, but I've been using them, both analogue and digital types, for the best part of 50 years at work and at home so am familiar with their use. Along with a DMM these are my favoured test instruments.

Having said that a multimeter is essential, if you do not have one get one before you think about getting a scope.

The main issues with test instruments are firstly knowing how to use them and secondly being able to interpret the results. The second issue is probably the most difficult for a novice to learn. With any measurement you make, be it using a multimeter or scope, you have to think is it what I was expecting, how does it compare with the values in the service data, is it in the right ballpark? This is what takes time to learn and is what the forum is about, helping people to understand and interpret their measurements.

Keith

[Argus25]

Originally Posted by mhennessy

Hand on heart, I wouldn't attempt to repair a Hacker without a 'scope. I'm not even sure I could. And having read this thread, I can't agree that there is a consensus to not get a 'scope. Given that suitable models can be found for less than £50

Well said.

And surely someone has to say this, the poor OP, all the mixed messages about scopes.

To reassure the OP:

In the same way it has been said that the eyes are the window to the soul, the scope is the window into time changing electrical phenomena. I would go as far as saying, without one, you will remain blind to the time changing electrical effects that make nearly every piece of electronic apparatus we all know and love actually work.

If you want to progress in electronics, get a scope, not necessarily the one I suggested, any type, play with it, get a feel for what is happening. Don't let anyone put you off. A scope is the closest thing on this Earth you will find to a crystal ball.

This is why you will see some people go "nutty" over scopes and collect many types (I'm a guilty party)... it is because they are that magic window into that apparently inanimate pcb on the desk in front of you and show you what is actually going on inside it.

Hugo

[ms660]

Local oscillator activity and approx. frequency check....'scope.

Ripple voltage check....'scope.

HT rail gremlin check....'scope.

AGC rail gremlin check....'scope.

Any gremlin check....'scope.

Mixer check....'scope.

AM IF amplifier check....'scope.

FM IF amplifier check....'scope

AM detector check....'scope.

FM detector check....'scope.

AM alignment....'scope.

FM alignment....'scope

Distortion check....'scope.

DC to Mhz voltage check....'scope.

Component test....'scope.

Square wave test signal....'scope.

Left and right compare....'scope.

Any two compare....'scope.

Go compare

And that's only some applications.

Lawrence.

[TonyDuell]

A few general thoughts.

I have the opinion that a 'digital' <whatever> is different from the (older, analogue) <whatever>. Not necessarily superior (in fact I can't think of a single instance where the digital version is _always_ superior) but different. A digital camera is different to a film camera (and both have applications). A digital storage 'scope is different to an analogue 'scope (and again both have applications). Fortunately nobody stops you owning both. You can end up with a CRT based analogue 'scope and an LCD-display digital 'scope on the same workbench, using whichever is better for the task in hand.

I learnt (as I suspect most people here did) with an analogue non-storage 'scope. This may colour our comments that when starting out it is better to use an analogue 'scope. Certainly you can do a lot with one.

But remember a 'scope (or any other instrument) is not a magic box that tells you what is wrong with a radio. It lets you look at signals, sure, but that's all it does. To put it bluntly, an expert with poor test gear will 'beat' a non-knowledgeable person who has the best test gear made. No question! And an expert will be able to use simpler test gear (such as a multimeter) to do what most people would need a 'scope for.

[Ed_Dinning]

Hi Bonky, a trip to the Golbourne vintage radio meeting in early Nov and you may find a suitable scope that the seller will demo to you.

Ed

[julie_m]

Now that would be an opportunity worth seizing with both hands, if it presented itself. You don't just get to see it working, you get a lesson how to work it, from someone who knows. That's even better than the guarantee you'd get with a brand new instrument. It will do all you need for now, and it won't have cost you so much that you won't be able to afford a fancier one if and when you do outgrow it.

[Bonky28]

Originally Posted by Ed_Dinning

Hi Bonky, a trip to the Golbourne vintage radio meeting in early Nov and you may find a suitable scope that the seller will demo to you.

Thanks; interesting, especially as my wife is a native of Golborne (Edge Green).

I’ll need to check dates.

BW

Richard

[SiriusHardware]

Originally Posted by MrBungle

Digital scopes haven’t done that for a number of years...

Well, you may have me there.

Current digital scopes are completely out of my price range so I have no experience with them. We can't even afford them at work.

You agree, though, that older digital scopes (the sort of age and price the OP might be looking at) are prone to displaying digital artefacts?

[MrBungle]

Yes, the PM3315 I had, which was a weird one was stuffed full of aliasing problems. There are certainly bargains to be had if you shop around. A friend of mine recently picked up a Tektronix TDS colour LCD based unit with 100MHz bandwidth for £73 at an online stock auction (not eBay which is ridiculous). That included buyers premium and delivery. That’s awfully close to the price of an analogue unit on the private market.

[Radio Wrangler]

Start with an analogue scope. Mankind managed OK with them for all except the last 15 years.

They are also without any doubt the best sort to learn on.

Thereafter, get a digital one if you feel the need. Professional engineers may get the business to buy the latest and greatest digital ones, but they still keep a good analogue one for special problems.

David