DIYHiFi.org

Thanks for the suggestions.

Is a 100MHz DPO (e.g., Tek TDS3012B) worth looking into?

Also, can you suggest a place to purchase a used LeCroy? Their new models are a bit out of my price range...

Thanks,
Bryan

Brand new 20M analog scope for $290 from http://www.elexp.com

jh

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Jim Hagerman

Hrm. I've gotta agree with Jocko on this one... 100MHz is the minimum I would look at. 20MHz is certainly OK for some audio work, but won't show a lot of the tantrums and operatic performances a misbehaving circuit may exhibit.

OTOH, there's something to be said for minimizing outlay on your first oscilloscope, until you've got some experience under your belt and have a better feel for what you want in a higher-end model. The ideal situation is to actually try out various models first, but not everyone has a friend(s) with spare scopes to loan out.

The TDS3012B is a good model, I'd definitely put it on my list of contenders.

Like Jim, I buy a lot of my test equipment on ebay. The 93xx LeCroys come up there often, as do most other brands and models you might be interested in. The independent used test equipment resellers (Tucker, tequipment.net, TestEquity, etc.) seem to gouge heavily, although they usually test, recalibrate, and/or refurbish their equipment and offer a guarantee. But, they're also targeting the professional market, so for a large company, the premium may not be an issue. If you're lucky, you may find somthing at a local estate sale, craigslist, surplus exchange, or swap meet. But even here in the 'silicon valley', where there is a high concentration of such things, finding a specific item is hit-and-miss. I don't know of another source besides ebay which will reliably give you a good chance of finding what you're looking for.

If you've never ebay'd before here are a few tips: Search the 'completed auctions' listings to see what kind of prices different models are actually going for before you bid, and be sure to check the seller's feedback profile as well to see that they have an established reputation on ebay and that others are satisfied with purchases from them. Feedback ratings of 99% positive or more are good reliable sellers. I get a bit suspicious below about 98%. Finally, take your time.

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- Chad.
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"Fashion is mistaken for good design; moral fashion is mistaken for good." -- Paul Graham

oops - didn't quite get this edit entered before the time limit: I meant to add that ebay requires patience. Price paid is roughly inversely proportional to patience applied. Anxious bidders are often seen driving the price of an item through the roof in the last seconds before it closes. I presume a fair number of those people regret their frenzied bidding to some degree later on, unless they've got cash to burn.

_________________
- Chad.
__________________________

"Fashion is mistaken for good design; moral fashion is mistaken for good." -- Paul Graham

Every time I buy from Tucker, I swear I won't do it again. They are right down the street, so it is tempting. The people who work there usually don't know squat about what they are selling. It could just as well be used cars, and that is the feeling I usually get. I did get a decent deal from them once, but that was only after they realised that their asking price was too damn high. So, they brouhgt it down to something more in line. I'm sure they pitched the ones they did not sell.

You (normally) do get the assurance of a recently calibrated piece. Not that exact calibration is needed, but at least you know it did work, and up to snuff, not too long ago.

Jocko

Hi,

I have got my scope (DSO3062A) today. It is pretty much what I expected - decent scope but nothing spectacular.

I have been using digital scopes for over 20 years, first Tek 7D20 plugin for 7000 series, then LeCroy LS140 and finally Agilent DSO6034A. What sets last Agilent apart is very high waveform refresh rate (about 100000 waveforms per second), so it feels like an analog scope. My new toy is more in line with the old Tek and LeCroy and displays around 20 waveforms per second ( this is an estimate since this technical data is not given). That means that you will not be able to catch infrequent glitches easily, although it has basic pulse triggering (triger on pulses wider or narrower than preset value).

Controls are normally responsive, although vertical channel positioning is a bit quirky. At first it is slow and precise, then it jumps about 4 vertical divisions. But I will get used to it. (In fact I just did).

What I do not like: Roll mode is not continious like chart recorder but repaints screen after screen. Menu auto hide is too fast for occasional use, although it is sufficient for someone working with the scope daily. Aliasing is a problem unless peak detect is used. For someone not used to aliasing scope could produce totally erroneous results. For instance, observing calibrator on 100mS/div produces DC value of either 0 or 3V. Autoset function works good though and should prevent much of those problems.

Would I buy it again? Yes.

Here is link to the user manual: User Manual

Best regards,

Jaka Racman

Great! Hmmm, I still use my 7D20 plugin. Probably the most modern piece of equipment I have. Use mostly the 7A26 and 7A22 for audio. Sometimes the 7A24 with a P6056 when I really want to know what those digital waveforms are doing.

jh

_________________
Jim Hagerman

One of the reasons I bought new scope is to repair my old 7633 mainframe. The company I work for had a dozen or so of 7000 series mainframes, but only two or three are still working. Usually it was the mainframe that failed, not the plugins. Usual problems were with focus, geometry and readout system. 4xx series is more reliable. We also have some 2xxx series of scopes and all of those still work very well. Digital scopes from that series (2430D or something like that) are total failure and are to be avoided. We had two of them and both failed several times so it was not economical to repair them.

Update on Agilent: menu on time is adjustable so this is not an issue anymore.

Best regards,

Jaka Racman