Oscilloscope for home duty

[radtech]

crud I've gotta learn to type faster...

[m8o]

Tom, Thank You!

And thanx for the link to govliquidation.com and annotation. Yep, wish there was a location on LI. But I don't understand, can one bid and purchase completely online? I don't understant how it's done.

edit: oh, never mind. Bidding isn't open on any of them. I get it now.

Thanx again,
Steve

[Pano]

I bought a used Hitachi a few years ago off eBay. Got it because it was local, so no shipping cost.

It has served me well. Not the best scope I've ever had, but great for the price. I'm happy.

[gootee]

Originally posted by m8o
Tom, Thank You!

And thanx for the link to govliquidation.com and annotation. Yep, wish there was a location on LI. But I don't understand, can one bid and purchase completely online? I don't understant how it's done.

edit: oh, never mind. Bidding isn't open on any of them. I get it now.

Thanx again,
Steve

Steve,

Usually, there's one good test equipment sale each month, at http://www.govliquidation.com . But it happens simultaneously at many of their warehouse locations. So just "keep an eye on" their site. And if you register, there, you should be able to "save your favorites", so you're (more) ready when bidding opens, on them.

Intelligent searching can save you a lot of time. For example, looking for FSC codes (e.g. "electronic test equipment" is "6625") can help. But looking for specific keywords is usually great, e.g. "tektronix", or "packard" (or maybe "hewl" instead), or, of course, "scope", although looking for common mis-spellings can pay off, too. Also, once you are familiar with which warehouse sites/bases are (fairly) nearby, you can use the Advanced Search to narrow things down, considerably.

You CAN "bid and buy completely on line", as you put it. But, you normally DO still have to physically go to the warehouse site that you bought the stuff from, to pick up the item(s), for the cost to be reasonable ([Hint:] unless you can form a network of friends near the various sites, who can ship to each other; BUT, some of the stuff is so "odd" that you just have to see it for yourself, to know... You could spend a lifetime looking at all the cool stuff they have... You'll see!), and, you have to pick it up within the allotted timeframe or you forfeit your stuff and get no refund!

Have fun! (I sure did!)

Once you get into the nitty-gritty, feel free to email me before committing, at tomg at fullnet dot com.

- Tom Gootee

http://www.fullnet.com/~tomg/index.html

-----------------

[DreadPirate]

Sounds like I've tapped the right well here. I'll go with Tek if that is the industry standard. Same reason I went with the Fluke 77 for a meter. This surplus site is great. I'm in the DC area, probably lots to look into. I'm going to have to get rid of some stuff first, I'm on a "one in" "one out" rule now.

[nhuwar]

Originally posted by gootee



Nick,

Maybe you were thinking about something in the timebase specs. The BANDWIDTH specification of an oscilloscope is simply the frequency at which the displayed amplitude is 3dB down from what it should be (based on the input's amplitude).

And, IIRC, most of the Tek scope models I've calibrated would display less than one cycle, for the whole CRT width, at higher frequencies than their bandwidth rating. At any rate, most scopes can at least _display_ signals that are higher than their bandwidth rating. But for input frequencies higher than their BW, the displayed amplitude is incorrect (usually on the low side by more than 3dB, with more error the higher the freq goes).

Some scopes also won't _trigger_ at frequencies that are much above their rated bandwidth. Some of the Tek 475 "200 MHz BW" scopes that I cal'd would trigger at over 300 Mhz. But some of them would only go to 220 MHz or less before the trigger just wouldn't "lock-on" to the signal, any more.


- Tom Gootee

http://www.fullnet.com/~tomg/index.html

------------------

My mistake Inever said I know everything I just thought I did

[eeka chu]

Our electronics lab at university is furbished with about 100 tektronix scopes, the budget TDS model or whatever it is. There are significantly better scopes available if you have money spare, but the TDS is pretty easy to use. The manual actually makes sense and it's all kind of easy.

I used to have a Fluke 123 Scopemeter, very, very easy to use, well made and useful to have to hand. But also not cheap.

[CBS240]

I managed to find a new BK Precision analog 30Mhz retail for around $350, in box, never used. Maybe not the cheapest solutieon, but it is absolutly impossible to design anything worthwhile without a scope. Should get many hours of use from it.

[m8o]

Somewhat OT, but related...

Question for those in the know, for the non-electronics-diy-newbz like me ...

If I want to check that my opamp-based amp does not ocillate, what MHz should I "check up to" ?

I ask, as this will define the ocilliscope bandwidth I should be looking for (and partially, how much $$$ I will need to spend). I have a -OLD- Heathkit scope my dad made when he took their self-study at-home courses. I'd like something better tho...

If that is too broad of a question to answer given all the variables that may go into it, is there a "frame of reference" that can be made based on the open loop gain frequency response of a opamp/device then? something like "check up to 1/2 the bandwidth" or "check up to twice the bandwidth", etc.?

thanx all

[gerhard]

Originally posted by gootee


Slightly less reliable (and with more "unavailable" Tek-custom ICs), but newer, lighter, and "better" in many ways, would be something like a 300 MHz Tek 2465 (or the A or B versions; 350MHz and 400 MHz).
------------------

Yes, the 24xx are well known to blow up their input amplifier hybrids.
You cannot repair them and you cannot get new hybrids from Tek.
Best to stay away or to check them carefully at least.

Gerhard

ps
I really liked the Iwatsu SS-5712, 4 ch 200 MHz, very bright,
excellent trigger, circuit is in the handbook, mostly standard parts,
one bad transistor in X-deflection in 20 years of service,
was easy to repair.