tips on buying an O-scope?

[mitsos]

Ok, so after about a week of nothing but trying to get my ssl9k up and running, I am running out of ideas, except taking it all apart and rebuilding it! ok, maybe not.

We recently moved to a small town away from civilization. To give you an idea, I don't have a DI. I never thought I'd need one here, but I ended up ordering one so I can use ProTools' signal generator and a home made probe to maybe get to the bottom of this ssl9k problem.

But since I am going to the states in a few weeks I thought I would get a used scope on ebay or craigslist or...wherever. I admit I don't know much how to use one, but I will learn as I go along. Plus, I've seen some older ones go for $50-100, and that's an investment I am willing to make if it means making better stuff.

I have bought from ebay before and have been unpleasantly surprised at times. And buying a used scope is pretty risky, I think. I'd like to avoid any brands/models that may have a reputation for being fragile/finicky or are hard to calibrate/repair, but is it a bad idea altogether to buy a used scope for 50-100?

Can you guys recommend any particular scopes to look for? Do I need a dual trace? Any brands and maybe models that would be less likely to be crap if bought used? If I have a chance to see it before I buy it, are there any quick tests I can do? (I thought perhaps I could put test tones on an Ipod, plug in a 3.5mm-3.5mm cable and probe the other end...would this work?)

I guess I could have it professionally calibrated before I go home, but how often would it need calibration after that? Is it something I can do myself?

sorry for all the questions,and maybe some are stupid, but hey, I can always say I'm new here!

Thanks!

 

[amorris]

old ones are scary if they dont come from someone you know.

just googled this one, Id buy it.

http://www.surplusgizmos.com/New-10MHz-Mini-Analog-Oscilloscope-Model-CA8016_p_131-1031.html

 

[mitsos]

Thanks amorris.
That looks nice and clean. I'm hoping to find one in Chicago as that's where I'll be.

I found some Tektronix ones (too old for my tastes) and the last one I was looking at was a BK 2120 (I think)...

I thought I read somewhere here that it needed to be dual channel.. Maybe I misread?

Also, will my testing procedure work (original post) ?

Thanks for the comments.

 

[amorris]

dual channel is nice but for $160?!?, I dont use the second channel that often honestly.

 

[s2udio]

[quote author="amorris"]dual channel is nice but for $160?!?, I dont use the second channel that often honestly.[/quote]
I find a Dual channel scope handy for In-Out Comparison and fault finding at any point in the audio path, two points of reference are better than one
IMHO a very handy tool for calibration :wink:
Evilbays ok if you are aware of the pifalls
160$ not a bad price,last a lifetme

 

[mitsos]

ok, so the dual channel will do 2 traces simultaneously right? btw, the dual on this site is 270.. Still cheaper than new.

s2udio.. about ebay.. I was wondering is there are known pitfalls with scopes? Like, I saw some old tube ones, I think I will avoid those.

thanks again

 

[wmtunate]

I picked up a Tektroniks 2213A on ebay a few months ago, but there were a lot of pictures showing it working on both channels, so I didn't feel bad about getting it. Plus, it was only $130 w/ buy it now, plus free shipping, which is about $70 less than the cheapest completed auction I saw at the time for that same model.

 

[bcarso]

Dual trace is extremely useful for many audio measurements. I wouldn't get a scope without it.

The Tek 2200 series scopes were pretty reliable, although the switches tend to wear out. I bought a 2236 new in 1985 and am still using it, although a portion of the range switch for channel B has an intermittent, and I patched a muffin fan on the back when the internal fan stopped working properly. Oh, and the built-in DVM failed a while back. So it is kind of the walking wounded, but I still find it useful. The frequency/time measurement functions are still good, and for frequency the counter inverts time interval for rapid high-accuracy displays, unlike the cheap function generator counters that count for increasingly long time intervals to get resolution.

Most of the time I have the bandwidth limit switch in for 20MHz, although for some purposes the 100MHz bandwidth is handy.

I also bought a 485 from Tucker and it still works for higher speed needs (350MHz). But I don't use it very much.

The predecessor 465 and 475 are both pretty good, and the 465 is pretty common and available I think.

 

[Svart]

http://www.circuitspecialists.com/prod.itml/icOid/9610

 

[bcarso]

[quote author="Svart"]http://www.circuitspecialists.com/prod.itml/icOid/9610[/quote]

Man that is cheap for a new DSO, even though the BW is low. I wonder how reliable they are.

 

[Svart]

I was wondering the same thing. I've seen the instek name around for years so I suppose they are decent.

If someone wanted to donate one to me I would be glad to try it out against a 15k$ Tektronics and an 80K$ Agilent scopes.. :green:

http://www.circuitspecialists.com/level.itml/icOid/1329

They have others, up to 100mhz, still for less than 1k$.. :thumb:

Check out their prices on soldering equipment too..

:shock:

 

[valvehead]

[quote author="Svart"]I was wondering the same thing. I've seen the instek name around for years so I suppose they are decent.[/quote]
My school just got a bunch of new Instek equipment. Among the new stuff were these 100MHz analog scopes. Not bad, but to save space/cost many of the buttons and knobs have multiple functions; you have to press and hold the buttons to access the alternate function. Also, things like AC/DC, GND, INV, and CAL status for each channel are only displayed on the screen in tiny text. Personally I prefer having buttons and knobs for every function and lots of status lights, but I guess I'm spoiled by my Tek 2246A.

 

[mitsos]

[quote author="valvehead"] but I guess I'm spoiled by my Tek 2246A.[/quote]
uh, yeah you are! Seriously though, I would like one of those, but I think buying it on ebay I am almost guaranteed a disaster.

After I posted I found a bunch of buying guides on ebay. I never noticed that when you searched, a whole bunch of guides came up on the lower left. Cool. So I'm gonna read through that and maybe try to come up with a few models to get opinions on.

But the more I think about it, the more I want to buy from a "real" store. Maybe the surplus place amorris posted, or maybe I can find a place in Chicago. I really don't want to spend more than a couple of bills though... Is it wishful thinking to expect to find a decent scope for that price?

 

[Svart]

I like the Tektronics DPO4054 that I use. Most of the other engineers hate it for some reason. They all prefer the Agilent scopes we have but I have learned the Tek pretty well and I guess prefer it because of that.

Makes it easy to find a scope to use though. I just walk around the group fighting over the Agilents and get the Tektronics.

:green:

 

[JohnRoberts]

I've got a TEK TDS 1002 and I like it...

There is a slight learning curve compared to old school scopes where buttons only do one thing, and only one thing every time, but the 1002 I got seems to be a little more user friendly than their earlier versions.

Or perhaps I just adapted to the new generation of equipment control,

JR

 

[mitsos]

Thanks everyone for the tips.. I've spent much of my free time browsing ebay for one.. found a couple of good deals, but not sure if I can really trust them to work properly. Anyone have an idea how much calibration costs?

 

[Marik]

I got Tek 2430A digital.
I still have my old Tektronix 2215 (60 MHz) in a good working order. If that what you want I might consider parting with it.

Best, M

 

[AnalogPackrat]

You can't go wrong with a used Tek in good condition. I use a 2235 100MHz, two channel, no frills from c.1984. Bought it used in 1995 and never have had a lick of trouble with it. I also have a big 7000 series storage scope frame (7834, I believe) and plug-ins for a 4 channel setup. Very nice, but big.

I bought the 7000 setup from John Bau in Santa Fe. He was a hi-fi speaker designer in the 70s and 80s, but now apparently plays tennis and sells test equipment. Check out his listings and give him a call:

http://www.users.qwest.net/~jbau/tstequip.htm

I have no affiliation other than being a satisfied customer. You'll pay a little more than on the 'bay, but the unit will work. If you've got the space you could get a 3 slot 7000 frame (7603, 7903, etc.), two dual vertical amp plug-ins and a timebase plug-in for under $500 and have a flexible four channel setup (you can get all kinds of neat plug-ins for these things and swap as you need to).

A P

 

[valvehead]

[quote author="mitsos"][quote author="valvehead"] but I guess I'm spoiled by my Tek 2246A.[/quote]
uh, yeah you are! Seriously though, I would like one of those, but I think buying it on ebay I am almost guaranteed a disaster.[/quote]
Really? I admit the chance of getting a bad unit is higher on ebay, but if you find a good seller it's not too risky. I got my 2246A for $255 on ebay a couple of years ago. No problems.

 

[bcarso]

[quote author="AnalogPackrat"]You can't go wrong with a used Tek in good condition. I use a 2235 100MHz, two channel, no frills from c.1984. Bought it used in 1995 and never have had a lick of trouble with it. I also have a big 7000 series storage scope frame (7834, I believe) and plug-ins for a 4 channel setup. Very nice, but big.
A P[/quote]

I would avoid the generation of Tek scopes after the 22XX period (don't know the models), before they pretty much got their act together again years later. Some of them were really terrible---I couldn't believe that one model that Harman bought had no ability to trigger A sweeps off of B signals!! Really stupid---I think these date from about the time Tek fired/laid off a lot of older engineers and lost the benefit of their advice.

They did develop one nice feature before going mostly DSO-ish, and that was the ability to see and set the trigger voltages on screen. Triggering btw really separates scopes from one another. It is highly nontrivial.

EDIT PS: other scopes with 23XX and 24XX had some excellent performers in the series. One of the amazing ones but very pricey had a tube with a microchannel plate that gave single shot low nanosecond rise time traces visible in normal room light---absolutely amazing and quite useful for some problems. I think that was the 2467?