Buying an oscilloscope

[UltraRC]

Hello, I am looking into buying a second hand oscilloscope, I found two and i'm not really sure how to tell if they are good or not.

first oscilloscope - http://www.trademe.co.nz/electronics-photography/other-electronics/other/auction-1165823188.htm

second oscilloscope - http://www.trademe.co.nz/electronics-photography/other-electronics/other/auction-1168355199.htm

Thanks

[tautech]

I'd advise you don't touch the Aaron, there's no manuals or schematics available for them.
How do I know? I've got 2, 1 working 1 not.

Old CRO's can be OK if you have the skills and equipment to keep them going along with another scope to help repair them when things go wrong.
Again, I've been there done that.

You can contact me directly about my TM listings and I can offer better deals direct. 

[oldway]

Unhappily, 20Mhz oscilloscopes are generally low end oscilloscopes for TV repair or beginners applications.

Industrial quality oscilloscopes are 100 Mhz bandwidth but they became scarce on used market.

Aaron oscilloscope looks like Hung Chang OS OS620 and you can perhaps use the schematics of this model to repair it. (I am not sure of it).

[R005T3r]

Are you on a very tight budget? If not, you can spend a little bit more and get a good item. If you are a beginner, get a decent instrument so it cant fool you otherwise it's over, because making and debugging project is hard and if instruments are misbehaving you will have a very hard time solving the problem.

Not to mention the fact that if you buy something at the real beginning and then you skill up with electronics you will be limited by the instrument itself and you will need to re-buy them again in the future, so be aware of that.

[kripton2035]

+1
sorry for insisting, but better buy a new rigol ds1054z if you're a beginner, you will learn from it a lot more
than one of these old and dusty scopes. the rigol is around $400 but they are really worth it.
may be if you can get these scopes for $20-$40 it could be ok. not more nowadays.

[edy]

I agree, Dave has a great video on buying old CRO's here:

I used his advice and picked up 2 oscilloscopes for under $1 per Mhz on eBay, shipping included! I received a 20 Mhz scope for about $20 and actually a better deal on a 100 Mhz Hitachi (with digital measurements) for $80. Both in good working condition. I also picked up a used 60 Mhz scope for about $30 in need of repair with a pile of probes.

So my point is, unless they are really CHEAP, do not bother. Older CRO's are practically being given away. You just have to be patient, don't overbid on eBay. Just find a listing that starts bidding at 1 cent, and put in AutoBid for Max bid at about $1/Mhz at the most. You may "lose" the item on the first few auctions.... but that's ok, you are really a winner because you didn't get scammed into over-paying for something. Eventually you will get an item that is not getting much interest and get it for substantially less.

Also, eBay tends to be expensive on shipping even if the CRO is cheap. So you should also check local classifieds listings. In Canada/USA at least, there are lots of ads in Craigslist and Kijiji, two popular online classifieds/personals listings. There are often many locals selling them for cheap and local pickup saves you lots on the shipping. Alternatively, get together with a local ham/radio amateur or electronics club, I am sure there are older members there who want to pass on gear to younger people who are just learning, often for free or a tiny amount of money (more a of "symbolic" or "token" amount to make sure you take care of it and not take it for granted).

Good luck!

[R005T3r]

I have to agree with above. Don't get scammed for an old CRT, don't have any sense.  I've had the opportunity to try a digital oscilloscope... It's all another thing: you don't have to count the divisions on the screen, you have a lot of more features and you can see what's happening better.

CRTs oscilloscopes are good for learning or if you don't feel comfortable in doing some kind of test.

[stj]

never buy a scope that is less than 50MHz,
that's the minimum you need for something common like adjusting the gain on a DVD laser assembly after you replace one.

and never lose control on ebay and over-bid on anything.
i am getting sick of watching a pair of people bidding stupid amounts against each other just to "be the winner".
know your top limit *before* bidding - and stick to it.

[alsetalokin4017]

Sure, buy a DSO for your first scope, unless you have some compelling reason (like budget or nostalgia) to get an analog CRO.

But don't get "lazy" and do know your basics. Don't rely on the "Auto" button, learn to set the scope up yourself to see the anticipated signal! Learn how to compute frequency by using the H setting and the graticule markers. Learn how to read Vpeak and other voltage values using the V setting and the graticule markers. Do not depend solely on "numbers in boxes", learn how to interpret waveforms visually by using the scope's settings and the graticule.