Low-cost oscilloscope recommendations

Don't overlook obvious freebies. Convince your boss that it's in his best interest for you to learn more. They may have something gathering dust that you can borrow.

Go find a ham radio club. Those guys often have spare scopes for their spare scopes in the basement. I have a spare TDS-540, if you can believe that insanity... mike

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FS 500MHz Tek DSOscilloscope TDS540 Make Offer
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Tek 465/475/485s are cheap and plentiful on eBay, IIRC.

Tim

-- Deep Fryer: a very philosophical monk. Website:

Thanks for the recommendations. The problem with eBay is that almost all of the 465s have no warranty/guarantee that they work although the seller says they do. If I paid $300 and got a dud I'd lose my money since I don't have a clue how to repair them. Any idea of any online stores selling used test equipment?

I'll look into the ham radio club thing since I've heard that before but have no clue what a "ham radio club" is and if I have any near me.

Thanks.

There are some on-line sellers of used test equipment, google for that phrase or for "used oscilloscopes" and you should come up with plenty. Ebay, however very well may be your best bet, though I do understand your concerns. Honestly, I don't feel that giving someone a "bad review" to be sufficient response to taking my money on a dud. While it would be possible to sue them, it would likely cost just as much. On the other hand, I know people who buy used test equip on ebay and they haven't had a bit of trouble.

A word of caution against a 100 Mhz scope: You are on the right track about bandwidth limitations. The scope bandwidth will significantly influence your ability to see higher frequency signals. Modern digital electronics have very fast rise and fall times, which correspond to significant engergy in the higher harmonics. In order to acurately view these signals you need a scope with significant bandwidth. The high speed / high frequency nature of these signals is independant of the clock frequency of your circuit, meaning that a simple and - or circuit implemented with LSI chips coiuld exhibit this behavior and FPGAs, which you mention using above, tend to have 'very fast' transition times. A digital scope would also be beneficial with regards to catching and non-periodic and non repeating signals which are quite common in digital circuits.

One thing to keep in mind is that I understand a lot of companies sell their outdated equipment on ebay when they are upgrading. What may be outdated for them could be a treasure for you.

I don't recall ever buying a scope that worked 100%. And it's not always obvious. Most have been easy to fix if you know what you're doing...and you spent 20 years working for TEK. The bad news is that it's really hard to fix a scope without a scope ;-(

If you buy used, try to get manuals and probes. It's not unusual for a manual to cost more than the equipment did.

Dealers can charge you 10X what it would cost to buy it right from an individual. There's a well-known test equipment refurbisher who sells equipment on ebay under an individual user name. "AS-IS No way to test it". I'd shy away from them, cause they damn sure can test it.

Go here:

Type in your city and call one of 'em up and ask about clubs, people who might have scopes for sale etc. The whole objective of the hobby is to talk to people you don't know. They'll be glad to hear from you. Once they get to talking, you'll probably find it hard to shut 'em up... 3 or 4 calls and you'll have a scope...depending on where you live.

Put a request on rec.radio.amateur.equipment and sci.electronics.equipment and craigslist. mike

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Wanted, Serial cable for Dell Axim X5 PDA.
Return address is VALID but some sites block emails
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FS 500MHz Tek DSOscilloscope TDS540 Make Offer
Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
http://www.geocities.com/SiliconValley/Monitor/4710/

I can't argue with "faster is better", but it's easy to delude yourself into thinking a faster scope will make it easier to debug a digital thing. Analog scopes are great for periodic signals. Problem is that your digital thing is far from periodic. Unless you can trigger the scope on the parameter of interest, it don't matter how fast it is. And the problems hardest to solve are the most intermittent. I have a GAL20V8 on a breadboard with flying leads as a trigger recognizer. I write a custom program for the GAL to optimize the sequential event triggering to see what I'm looking for. Tedious, but powerful.

The sweet spot of price/performance for analog scopes is 50-100MHz. Much faster and they've got too much custom stuff inside and can't be repaired by mere mortals. I'd vote for the TEK 465 family. 7704 mainframe scopes can be had dirt cheap, but get 'em with plugins. Ebay nickel-dime you into the poorhouse filling up the holes. Snag a full system with manuals and probes.

mike

--
Wanted, Serial cable for Dell Axim X5 PDA.
Return address is VALID but some sites block emails
with links.  Delete this sig when replying.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
http://www.geocities.com/SiliconValley/Monitor/4710/

Here's a recent article about some of the PC-based oscilloscopes, which seem to be a pretty good value:

ttyl,

--buddy

Although its been mentioned a number of times before, ebay is the way to go. Just make sure you buy from a seller with 99% or above and you will likely be fine. I bought my scope there and it cost me half of any other place I looked. As long as it is not *collectable* ebay is a great place to buy stuff cheap IMHO.