choosing an oscilloscope

floid · Post by **floid** » Wed Aug 26, 2015 8:30 pm

So, I've enrolled in an electronics program to try to round out some things. Today we played with an oscilloscope, and I realized just how useful one could be for me. But I've got no idea where to begin. For diy that's progressing beyond recaps, internet mods and projects, and textbook examples, what do I need in terms of... what? Digital v. analog, how many channels, resolution, range...

The Scum · Post by **The Scum** » Wed Aug 26, 2015 10:29 pm

The first thing I look for is the name "Tektronix."

On a limited budget, check Craigslist, maybe track down a Tek 465 - A really classic analog, 2-channel scope. $100 is a good deal, if it includes probes.

For most analog audio work, a 2 channel analog scope should be sufficient, maybe 5 or 10 MHz bandwidth.

If you're ever considering working on tube circuits, make sure the inputs can handle up to maybe 500 V, usually through 10x probes, meaning a max printed scale of 20 or 50 V.

If you're moving into higher speed digital territory, higher bandwidth is a good idea, and probably a digital scope with more channels...though a decent analog scope, supplemented with something like a Saleae logic analyzer makes a pretty good combo.

dfuruta · Post by **dfuruta** » Thu Aug 27, 2015 7:26 am

Buy a used analog two channel 20MHz scope off eBay. You should be able to get something for $50, plus $20 for some probes (those crappy no-name ones you find everywhere will work fine). You won't be able to get anything decent & digital unless you're willing to spend much, much more.

If you can find a Tek 465, it's a nice one. I'm using a 475A now and it's great. But, any reputable maker will be fine. My first scope was a Panasonic, and I have no complaints.

Avoid those cheap digital "pocket scopes". Don't buy new - older used test gear has very little resale value, and so you can get the state of the art from 30 years ago (which is sufficient for most audio stuff) for less than new crappy hobbyist-oriented junk.

You'll probably want to pick up a function generator and some bench power supplies as well. Buy those used too.

Drone · Post by **Drone** » Thu Aug 27, 2015 6:37 pm

If you go the analog route, always make sure you can get the trace nice and focused, a big blurry trace is no good atall.

Make sure you have it triggering PP-AUTO so that you get a trace even with no signal, and use the position knob to sweep that trace up and down the screen, this will find burnt spots, and busted CRT's.

Also be aware analog oscopes are nice, but without a current calibration they are only indicative of something, and in no way should be considered a 'measurement' tool, those things can drift far out, fast. I was a TEM tech in a previous life.

floid · Post by **floid** » Sat Aug 29, 2015 8:59 am

Thanks for the input.
Craigslist doesn't work the same around here, it's mostly tires and power tools. There's an old RCA down on the coast, a few others in Nashville or Birmingham... Hard to justify driving three or four hundred miles to spend less than $100.
eBay seems to think 465's are worth $250 and up for units that are anything other than "untested/ for parts". It's tempting to think in terms of "recently calibrated."
There seem to be a few variants: 465b,m,tas. And the 453, 466, 475. And then the 22xx series. Some have add-ons like a dmm etc.
And then Philips/fluke, Hitachi, Panasonic, etc.
It's all a bit overwhelming. I think patience will be a virtue here, but I'm trying to get a handle on how picky to be.

Drone · Post by **Drone** » Sat Aug 29, 2015 9:21 am

22xx are the series after the 400's, if they are cheaper snap one up. They rock.

Matt C. · Post by **Matt C.** » Sat Aug 29, 2015 11:50 am

I've got a Tektronix 2215. works great, got it for maybe $100 on Ebay. Pretty standard 2 channel scope, 60 MHz bandwidth I think, which is sort of overkill for analog stuff. I wish I could find a place to get it serviced/calibrated but it seems to be accurate enough for my needs at the moment.

Tektronix is the big name company but plenty of other people made usable scopes, so if those are cheaper, go for it.

Drone · Post by **Drone** » Sat Aug 29, 2015 11:54 am

Well, the place I used to work got bought by Tektronix. I have no idea what a cal goes for these days, probably about the same as what you paid for the scope.

dfuruta · Post by **dfuruta** » Sun Aug 30, 2015 9:33 pm

Don't think you have to get a Tek or HP; there were many American, European, Japanese companies making nice scopes. Don't worry about calibration too much. Even a grossly out of calibration scope is going to be adequate for most of what seems to come up in audio electronics - building fuzz boxes and tube whatever or fixing your power amp with the blown up output transistor ain't precision shit. And, one would hopefully not be using a scope anyway for accurate distortion or voltage measurements.

floid · Post by **floid** » Fri Sep 11, 2015 5:27 pm

How does the 466 compare to the 465? I can't seem to find much on it.

Drone · Post by **Drone** » Fri Sep 11, 2015 6:18 pm

It's comparable to the 465 but with storage, analog storage is kinda weird, you'll see.

http://w140.com/tekwiki/wiki/466

Manuals are in link.

floid · Post by **floid** » Sat Sep 12, 2015 7:23 am

So is the CRT the difference? Is it a better or worse scope? Extra features or more suited for a different application set? I ask because I've learned the 465m is not the same as the 465 and 465b.

Drone · Post by **Drone** » Sat Sep 12, 2015 4:38 pm

It's a scope, the CRT's are harder to get, though honestly if you bust the CRT you might as well scrap it on any of them.

For audio work, they're all much the same.

dfuruta · Post by **dfuruta** » Sun Sep 13, 2015 1:09 pm

A storage scope should let you turn the storage function off. A storage scope isn't necessary.

Drone · Post by **Drone** » Tue Sep 15, 2015 9:32 am

Saw this, may be helpful, didn't examine it as yet

http://www.instructables.com/id/Oscillo ... cilloscop/

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choosing an oscilloscope

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