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Tek TDS220: Is it worth the money?

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Dr. Shark

Fri Feb 17 2006, 10:03AM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

I am a total gear whore and I am totally in love with this ever since I used one when I was working in a lab some 5 years ago. Should I buy one?
The scope I've got at the moment is an ancient crappy Hameg 20Mhz one, the timebase does not go below .5us/div and it doesn't do any digital readout. Its definitely not good for SSTC work, and completely useless for pulsed stuff (railguns, can crushers). On the other hand a lot of people here seem to get along well with no scope at all.
I would try to get one from eBay for 600â‚¬ or so, which is a lot of money for me. If I decide to sell it again in a few years (no more time, different job, kids, whatever reason) it is still going to have most of its value, if I dont break it, that is. Should I be worried about breaking it? I suspect the digital stuff is much more sensitive to things like TCs and discharging Marx gens near it that the analog counterpart would be. Maybe an analog scope would be the better choice for this kind of work?
I really cant decide, so, please, why dont you decide for me?

ragnar

Fri Feb 17 2006, 10:58AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

I suffer from flagrant indecision, too.

Until it died spontaneously overnight (probably an intermittent problem which the owner failed to identify when selling it to me...), I kept my scope in another room when developing stuff.

I have a $30.00 multimeter (a particularly nice one for the money) from electus distribution which I use as my oscilloscope. With some practical intuition, you can get away with just a not-too-crap multimeter for most of it. My meter had ~10MHz frequency counter, capacitance measurement, fast AC volts (unlike some really cheap meters which will only read AC volts cause they use 1N4007s inside!!!) etc.

I can use it to guess at what my gate waveforms are like for voltage... with the frequency counter I can tell if they're really nasty because it's reading 2x the frequency going in, which usually means a ringy waveform. If you've worked with a single multimeter for a long time, know exactly how it behaves inside out, it's a great semi-disposable tool for a lot of projects.

As I was on a student's budget (and initially unfamiliar with the scope - needed to read up about isolated inputs etc), my $152.00 scope (including shipping) was something that I only dared to apply to the kind of circuits you could carry around. Forcing myself to keep it in another room meant I wasn't tempted to just pop it onto a running fullbridge to look at the DS volts. Just about anything that needed scoping that I was building was logic, PLLs, oscillators etc etc, which can usually be carried with a 12V battery to my bench with the scope. No fear of destroying the scope, I never killed the multimeter, and I got a heap done.

I was heartbroken when one day I turned it on and she no work no more. You really miss it once it's gone, I'll tell you that, hehe.

Forgive me for waffling on or so long... you'll know what will work for you... depending on your budget, you might be able to do something like what I did, but the next step up - e.g. you've got a $50.00 20MHz scope which you can confidently go near resonant circuits with, and when you're doing finer stuff (or when you need the scope less often but for fiddlier, more-time-thinking-about-them operations like looking at the pulse shape on a coilgun) you can bring in your nice 600-euro scope and take care.

Don't sell the lil scope, buy the nice one, and take care of it. If you're not using it much, it was a good investment which you can clean up and pass on (maybe even for more than purchasing price) on eBay.

Digital scopes by tektronix I've found to be an absolute pleasure to deal with. I've worked with two models of those LCD scopes, and they speed things up, especially with the "Autoset" function (although mostly I really prefer to have control over what signal I'm seeing).

Perhaps you can find a cheap CRT which does 'digital' (trace) readout and has simple storage functions, then blow six hundred euros on a digital scope when you find it's not doing what you need. The digital scopes aren't necessarily more sensitive to marx discharges etc - they're usually very well shielded, but the difference is if you kill a digital scope, you don't even bother taking the case off. :'(

Any warranty available? I guess, think about the risk vs reward... are you really going to risk a digital scope near that stuff? I wouldn't trust myself, which is why I keep it in another room, but if you're an equipment-whore, you'll know what you're doing and when to remove those probes ;)

happy scoping X-)

Steve Conner

Fri Feb 17 2006, 01:02PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I do something much like what blackplasma suggested. I have three scopes just now:

A battery-powered 20MHz unit that I was given for free (ok it was broken, but easily fixed) that I use for dangerous jobs that might end in disaster. I'm not too bothered if it gets killed.

A big 4-trace 75MHz scope that I use for everyday work. It's a Tektronix R7603, a model from the 1970s that I bought second-hand for about $150. I think it was military surplus. It's not perfect, the on-screen readout sometimes gets scrambled, but whacking it usually fixes that.

For those real stubborn stains that an analog scope just won't shift, I have a Pico ADC212-100. This is a 100MS/s digital scope adaptor that plugs into a PC parallel port and displays traces on the PC screen. I use it with an old ThinkPad laptop, and the whole setup can be run off a SLA battery, which helps to isolate it when making SSTC measurements.

It's maybe not quite as good as a dedicated digital scope, but it seems plenty good enough for everything I've used it for so far. It has a huge 32Ksample buffer that makes it great for capturing DRSSTC bangs. One thing I keep meaning to get round to, is fitting the "ScopeTop" with a wi-fi adaptor so I can control it remotely with VNC for those high voltage floating measurements.

Anyway, the TDS220 is a great scope. It's pretty much THE digital storage scope. It seems to hold its value well which is great if you're selling, and a pain if you're buying :( However, Tektronix recently discontinued it (the replacement is the TDS2012 IIRC) so it may get cheaper. We have one in the lab at work and it is great for just about everything, except sometimes a good analog scope can show more detail when you are trying to track down noise and parasitics.

We have one of those 20MHz Hamegs at work too. It lies in a corner and I usually kick it when I go past, if I can be bothered

Eric

Fri Feb 17 2006, 06:33PM

Registered Member #69 Joined: Thu Feb 09 2006, 07:42AM
Location:
Posts: 116

I had a TDS210 and thought it was a a great little scope. I suspect it is physically more durable than older, less integrated digital scopes. I bet you could get it serviced (if needed) for a reasonable price too since it's a fairly current model.

What I didn't like was the short record length (basically just one screens worth) and the fact you can't use Tekprobe probes with it. I replaced the 210 with a TDS420A, which is a step down in some areas but had a long record set, FFT, 4 channels and the Tekprobe interfaces. Using it with the P5205/P5210 probes for direct, differential HV+HF measurements is very cool!

If you look you can get a 420A for 600-800 now.

Avalanche

Fri Feb 17 2006, 06:34PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

I do like those Tektronics, I had one on my desk at work for months when they bought a Fluke scopemeter. I don't know why, but everyone seemed to prefer the Fluke, even though you had to go through a menusystem to alter anything. (I took the rip out of them).

The Tektronic did survive a couple of scary moments at work :

1) An ignition coil driver that messed up my monitor did not affect the scope (yes this was at work)
2) I connected the Tektronic directly to a spark gap - using some resistors! Probably not the usual thing to do, but it did fine.

...So I would say it is fairly robust.

HV Enthusiast

Fri Feb 17 2006, 07:37PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

I personally don't think they are worth the money.

If you are looking for a good digital storage scope that costs much less (you can get them for $300 USD if you look hard enough), try the Tektronix 2430A. These are great scopes and provide on screen measurements, digital storage, etc...

If you are really going to invest a lot of money in a scope, then go for one of these . . .

Tektronix TDS540 series (about $2000 on EBAY - 4 channel, 500MHz, loaded)

If you do get a portable tektronix scope, make sure it at least as the printer port (parallel) and floppy drive options.

Hazmatt_(The Underdog)

Sat Feb 18 2006, 07:07AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

My dad hinted that I could have a scope as a B-day gift, but I assumed that Tek would be out of my range unless it was at the swapmeet. I'm gonna look for the 2430A right now!

Dr. Shark

Sun Feb 19 2006, 07:54PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Now I am really confused by the use of scopes Black and Steve are hinting at.

In the kinds of experiments I am doing, the greater the risk for the scope, the better it needs to be: To capture discharges on a railgun or Marx generator I need a fast storage scope, whereas some low-voltage logic circuits could well do with an analog scope. In the same way, I need lots of MHz if I want to capture bangs on a DRSSTC, but 20MHz will do if I debug the logic circuit on its own. So it really seems that I should not get the Tek, since the stuff I was going to use it for is exactly the kind of stuff people suggest I should not do with it.
Well, the scope I have now is not as bad as I made it, it actually used to do digital storage, but that never worked correclty since I got it used. It also goes up to 20ns/division if I crank all handles, so I guess I might aswell stick with it until it dies, or I have money to burn a Tek.

Hazmatt_(The Underdog)

Mon Feb 20 2006, 03:38AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

WOOO! Got my Tek 2430 for $370!!

Ima Happy!

Dr. Shark

Mon Feb 20 2006, 08:37AM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Well, happy birthday! Hope you'll have fun with it.

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