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View Full Version : Would this oscilloscope be a good buy for testing old equipment?



arrow_runner
July 2nd, 2013, 12:12 PM
I have the opportunity to pick this up locally for $150. Would this be good for troubleshooting old 8/16-bit machines and building small circuits?

http://www.mcmelectronics.com/product/TENMA-72-8395-/72-8395

Chuck(G)
July 2nd, 2013, 12:47 PM
For slower systems, it should be okay--the sampling rate will be adequate for most tasks. Do you know how to use a scope?

arrow_runner
July 2nd, 2013, 12:52 PM
No, I have not used one before

Chuck(G)
July 2nd, 2013, 01:01 PM
Okay, there are some good YouTube videos on "How to use an oscilloscope" that you might want to watch before you start poking things.

arrow_runner
July 2nd, 2013, 01:04 PM
That was the plan, but good advice nonetheless. Thanks.

When you said slower systems, what did you mean exactly? I'd expect that I'd use this mostly for 8-bit systems up to 8086 class machines, though being able to troubleshoot 386 and 486 boards would be a huge plus.

Chuck(G)
July 2nd, 2013, 01:38 PM
Well, again it depends upon what you're using the O-scope for. Note that the sampling rate is pretty fast 250MHz dual-channel and 500 MHz single-channel. So the question is if you're looking for very short pulses or accurate rendering of fast analog waveforms, the Nyquist limit is going to play hob with that--and that's why you need to oversample.

But if you're looking for "I see a high" or "I see a low", your scope has quite a bit of headroom. That's why, for example, the combo logic-analyzer/DSO setups have much higher frequency limits on the logic analyzer frequency than the DSO part does. The 'scope cares about accurately rendering the wave shape, while the logic analyzer only cares that there's something there or not--shape be damned.

I'm going to guess that you're going to be using the scope as a logic analyzer. In that case, it's suitable for just about any vintage computer you're going to use it on.

smp
July 2nd, 2013, 03:04 PM
Hi,

Is there some reason that you are going for a digital scope?

There are many used analog scopes available for much better prices. Here are a few samples from eBay:

http://www.ebay.com/itm/TEKTRONIX-466-DUAL-TRACE-DIGITAL-STORAGE-OSCILLOSCOPE-2-CHANNEL-100-MHz-/300926325509?pt=BI_Oscilloscopes&hash=item46109b5305

http://www.ebay.com/itm/TEKTRONIX-MODEL-2336-100MHZ-OSCILLOSCOPE-/221247097606?pt=BI_Oscilloscopes&hash=item33835acb06

http://www.ebay.com/itm/Tektronix-2225-50MHz-2-Channel-Oscilloscope-/200939719660?pt=BI_Oscilloscopes&hash=item2ec8f0cbec

I lucked out and got a Phillips PM 3216 35 MHz analog oscilloscope for $45 at a local electronics recycler. Those bargains are the kind that you don't think twice about!

Good luck to you!
smp

xprt
July 2nd, 2013, 03:39 PM
Note that the sampling rate is pretty fast 250MHz dual-channel and 500 MHz single-channel. So the question is if you're looking for very short pulses or accurate rendering of fast analog waveforms, the Nyquist limit is going to play hob with that--and that's why you need to oversample.

I guess Chuck is saying that the limiting factor here is the analog bandwidth of 25MHz, not the sampling rate. The rise time is specified as 14nS. That gives you a ballpark idea of the fastest clock rate and pulse width you are going to be able to deal with.

edit - Ballpark means that you will be able to still see waveforms at these frequencies, but they will be somewhat distorted. 25MHz is typically the 3dB bandwidth, so a sine wave will display with only 70% of its true amplitude at 25MHz. A square wave will also be attenuated and not look very square. You will only be able to go up to about 5MHz if you want a nice looking accurate waveform. But as Chuck pointed out, for digital work you can push close to the bandwidth limit of 25MHz and still be able to see pulses and timing relationships.

As for analog vs digital storage scope, you can catch glitches and one-shot events with a digital storage scope, but not with an analog scope.

dorkbert
July 2nd, 2013, 03:40 PM
not sure if the OP quote included the probes, but most fleaBay listings generally don't include them, can they can cost a pretty penny in addition.

NeXT
July 2nd, 2013, 04:09 PM
I bought a 10x probe set for $20. It doesn't break if you buy a scope without them.
I would also recommend one of the many HP or tektronix scopes available over a new off-brand product. You get a crazy amount of slack to work with that you will probably never use.
Actually, just watch this. (https://www.youtube.com/watch?feature=player_detailpage&list=PLF591F766C6B44497&v=qIfo_-d82Co#t=68s)

I bought my scope about four years ago for $10 and I've never needed anything better considering it's 25 years old.

Chuck(G)
July 2nd, 2013, 05:20 PM
I'm still using my old Tek 465B--not a thing wrong with it.

Dwight Elvey
July 6th, 2013, 05:58 AM
Both analog and DSO have there purpose.
I just bought a nice DSO. Two channels do 200Mz
sampling at 8 bits and 2 are 10MHz at 12 bits.
It has all kinds of triggering options that make it close
to a logic analyzer with only 2 channels.
It even does FFT's on signals.
I still have a 100MHz analog scope for general work but
with the sampler, I can capture, say the D0 and D5 of the
data but 20us after the 30th time it read the USART and
capture 20 bus cycles.
I know one could do that with a logic analyzer but I can
also see the slight dip in one of the signals caused by
a weak bus drive on D5.
I can build up the entire bus with recorded captures on disk.
As chuck says, you do need to understand digital sampling and
the limitations. Things like aliasing can drive you crazy if you don't
understand them.
Dwight

JGardner
July 13th, 2013, 06:00 PM
Any Tek 556 users still out there? :)

Four-Phase
July 15th, 2013, 08:14 AM
14368
First I want to express my respect for Chuck and Dwight Elvey.
Both of you are so well verse in the operations of Oscilloscope.
(must be from an electronics background)I guess.
I have with me a vintage scope around 30 years old. A 10Mhz type...dual channel.
I received it in "KIT-FORM" and assemble it myself from a correspondence
course I took then. It didn't really work well until one year after finish assembling it!!
due to poor soldering...hehehe. It serve me so well until it broke down again and again.
I kept it until today. A lot of good and not so good memories inside. so today I am showing off
this to everyone here...any comments??

glitch
July 15th, 2013, 09:14 AM
My first 'scope was a Heathkit OL-1, which someone had (poorly) assembled into a nonworking doorstop -- I think the guy said he never got it working. It was more or less a "waveform viewer," as its controls were all pots and there was no graticule at all. All tube, so what you observed on the CRT was different after it warmed up. I learned a lot about low-frequency RF and AF electronics with it, though!

I finally got a real 'scope in college, a Tektronix 7000-series mainframe. I still use it as my primary oscilloscope today. It's more than adequate for the hobby digital and analog electronics I work with, and it cost $75 from eBay 5-6 years ago. Since it's a mainframe unit, you can swap the sweep and input modules if you need different functionality.

Chuck(G)
July 15th, 2013, 10:07 AM
Tying this thread in with vintage computers, does anyone have one of the little NLS (makers of Kaypro) scopes?