I am looking to purchase a used unit from craigslist, I was wondering if the ones listed below would be a good choice, and then what are some basic tests to make sure the unit works. I am experimenting with AC alternator design and need to make accurate measurements.

Hitachi Model V-660 ($170 OBO)

TEKTRONIX 2336 ($300)

TEKTRONIX 2220 (make offer)

Thanks in Advance,
Ken

 

I have a Hitachi V-660 in my basement workshop and it has served me well. I bought it a few years back off of the internet so I could do some home power supply design. I now use it for much more than just that...

The first check I did with it was to connect the A and B channels up to the calibration point on the front of the o-scope. It provides a 5V square wave at 1 kHz which should be easily seen by both channels. Make sure the voltage and frequency is close to what you expect.

 

Another convenient source of test signal is 60 Hz from the power
lines. Use a small transformer, say 6v or so, plugged into the
wall as a source. While a sine wave, unlike a square wave, does
not really test a scope's ability to display signals correctly, you can
use it to check that the triggering works properly.

 

I can't comment on the models listed, as I have no experience with them. But I have two scopes purchased over the last 30-40 years and a loaner from a test equipment company, so I do have some opinions.

First, decide if you want an analog or digital scope. Frankly, over the years I've liked the analog scopes better than the digital scopes (especially with regards to triggering, which I consider the most crucial performance aspect of the scope). But the digital features are just too nice to have, especially the ability to store a transient and very slow waveforms and get them into a form that can be read by a computer. Those two tasks are a challenge with analog scopes.

I use a rule of thumb of my own making in judging the bandwidth -- I divide the manufacturer's stated scope bandwidth by 20 and use that as a rough guide as to the range of useful signals I'll be able to measure. The reasoning is that this lets me look at a number of harmonics of that fundamental, meaning I'll be able to roughly see a square wave when that's what the true signal is. Thus, my 100 MHz scope is quite useful for 5 MHz or so square waves.

 

You can try to look for used oscilloscopes here. Its previously used for test equipment.

 

If you're looking in the $300 range, you should consider getting a new DSO such as a low-end Rigol or Owon scope. The Rigol DS1052E, 50 MHz is about $399 on eBay, and it comes with a 1 yr warranty. And there is a way to hack the DS1052E and turn it into a DS1102E which is a 100 MHz model by a few commands (look it up, it saves you $300 extra.)

It's worth saving up a bit extra for a new digital oscilloscope, because it lets you do so much more. Some say you should also keep an analog scope around because they're better for some things, but it depends on what you want to do.

 

I got a really nice used TEK off ebay.

 

I also have a Hitachi V-660 60MHz dual trace that is quite handy that I got for dirt cheap. Mine has a bloom on one edge of the CRT, which is why it was so cheap - but it's very usable. I have not found a source of parts for it; the CRT is not stocked anywhere that I can find.

I also have a Tektronix 2215, which is very similar to the 2220 you're considering. It's a very nice 60MHz dual trace. However, it's a bit larger than the Hitachi, and I needed maximum space in my work area - so the Tektronix is in storage as a backup. Hard to beat a Tektronix scope.

I am a fan of the older analog scopes. You can fix them if they break, and also calibrate them, unlike the new digital scopes.

Manuals for older 'scopes can frequently be found on websites like Bama's "The Boat Anchor Archive". Having a service manual is a boon, as with an older 'scope one of the first things to do is replace ALL of the electrolytic capacitors with fresh ones. Failure to do so may result in destructive failures and difficult repairs.

 

If you don't need real high bandwidth this is a pretty good deal for $89:

http://www.pdamusician.com/dpscope/index.html

 

Just discovered that link to my site (I'm the designer of the DPScope mentioned in the post above).

Frequency-wise the DPScope should easily cover the range necessary for power-supply and alternator work. Note that while the input of the scope is limited to 20V, you can measure up to 200V with a standard 1:10 scope probe. The scope input itself is protected (larger series resistor at the input followed by clamping diodes) and will withstand at least 200V without any damage to the scope or your computer (so with a 1:10 probe you are safe up to whatever the probe itself is rated to since only 1/10th of the voltage makes it to the scope).

If you can spend more (~$400) I can also recommend the Rigol DS1052 scope - I have the 100 MHz version (which is identical except for software-enabled higher bandwidth) and like it a lot.

Regards,

Wolfgang

 

Wow, an old thread gets resurrected and we meet a scope designer.

He must really read his log files.

 

Or someone on AAC sends him an email...

By the way, I really like the product and price point this guy has put together -- he makes a nice looking scope available at the price of a DMM. I don't need another scope, but I hope he makes a few sales from his exposure here.

 

I just reread your post, and it addressed my point... silly me.

 

I got both my scopes for free from FreeCycle. Depending on your area it can be an excellent source of scrap electronics. Most FreeCycle groups use Yahoo! Groups, so just do a search.

Its generally filled with coat hangers and kettles, but if you ask nicely, almost always someone has got a scope in the attic from "years back" they don't use any more.

(Don't expect fancy stuff)