PDA

View Full Version : Oscilloscope Recommendations



CommodoreKid
November 9th, 2014, 05:17 AM
It seems that I find myself borrowing an oscilloscope more and more frequently (it was instrumental in reviving my H89). However, I think I've reached the point where I just need to buckle down and buy one of my own.

Therefore I'm curious as to what kinds of scopes y'all have found to be the most useful in diagnosing and maintaining your vintage computer collections. What kinds of specifications have worked well for you?

Uniballer
November 9th, 2014, 06:00 AM
It depends a lot on what you want to see.

The first scope I used on the job in real life was a Tektronix 465 (100 MHz cathode ray oscilloscope). It was good at showing repetitive events, and that *something* was happening on less repetitive events, but was useless for one time events, or decoding bit streams, or whatever. This is, however, the general kind of technology that a design engineer or technician might have used on your vintage stuff back in the day. Historical note: the phrase "Cavemen used oscilloscopes to debug fire" was referring to the Tek 465, or maybe the 454, and comparing them to primitive logic analyzers. My Tek 475A (same thing but 250 MHz bandwidth) is generally still my scope of choice for digging into switching power supplies, etc.

I have a now-old Tektronix TDS380 (2 giga-sample/sec 8-bit digital storage scope with a 400 MHz front end). Nice for capturing edge-related problems, but memory is too limited for decoding bit-streams, etc. I keep a similar 50 MHz TDS310 in my office at work, just for general-purpose troubleshooting and to look at 1-Wire signals.

Some of the newer Rigol units are well spoken of for workhorse use. Bandwidth of 50 MHz and up, possibly with serious memory depth.

Bandwidth: a 100 MHz scope allows you to see a 100 MHz sine wave. You might need a 500 MHz to 1 GHz scope to see a 100 MHz square wave accurately.

Channels: 2 is the absolute minimum. Four can be very useful, to the point that many people who get used to a four-channel scope will not go back to 2.

A logic analyzer or protocol analyzer might be better for showing you some things.

SkydivinGirl
November 9th, 2014, 06:07 AM
I'm still very new to working with scopes, but I like the 2 Channel 100MHz Rigol that I picked up. It also reviewed well and I think it will get me through most of my hobby needs.

Heather

modem7
November 9th, 2014, 10:15 PM
Logic State Analyser

I use an Intronix LA1034 LogicPort [in-action photo (http://www.minuszerodegrees.net/images3/5170_la_in_use.jpg)]

Oscilloscope

* In the digital arena, good for 'is there something there?'
* In the digital arena, good for 'repetative signals' (e.g. sync pulses, clocks)

* These days, I use an ATTEN ADS1102CML
- Digital
- Wide screen
- Can copy screen shot to USB stick [example (http://www.minuszerodegrees.net/ibm_xebec/ibm_xebec_step_pulses.htm)]

gslick
November 10th, 2014, 07:58 AM
Some of the newer Rigol units are well spoken of for workhorse use. Bandwidth of 50 MHz and up, possibly with serious memory depth.


If I was going to buy a brand new scope on a budget I would probably take a look at the Rigol DS1054Z. For $400 that is probably hard to beat for something brand new. Here is the EEVblog look at it and there are a lot of other videos and reviews out there, and information on how to unlock the upgrade codes.
https://www.youtube.com/watch?v=kb9P1Am9aFU

I bought an Agilent InfiniiVision 3000 X-Series scope, but I wasn't on a tight budget.

sergey
November 10th, 2014, 04:03 PM
Rigol also makes mixed signal scopes. They are more expensive (about $800), but logic analyzer function is really useful for debugging digital circuits including computers.
Tektronix DSO/MSO2000 scopes are also nice (but more expensive than Rigol). MSO version in addition to parallel bus debugging, can analyze/decode serial buses (e.g. I2C, RS232, SPI), but that requires an additional software key...

tipc
November 10th, 2014, 05:14 PM
My advice - get something dirt cheap at a flea market, craigs, or ebay. Then go from there. Shoot for a sampling rate of at least 3x the frequency of what you expect to be looking at. For the most part I think you'll simply be looking for the presence of square waves, not scrutinizing rise and fall times or whatever.

CommodoreKid
January 5th, 2015, 09:12 PM
Jackpot! I got exactly the kind of present I needed for doing the kind of repair work I need to on my vintage computer collection: a Tektronix 2445B. It's got 150MHz bandwidth, 4 channels, a few cosmetic scuffs, and markings indicating that it was last calibrated in October of 2013 by the previous owner if the stickers are to be trusted. I just need to go and buy myself 4 proper probes to replace the two that came with it (they are in bad shape).

22042

m_thompson
January 6th, 2015, 04:26 AM
I have a Tek 2432A, the 2 channel, 250Mhz version of the 'scope that you have. They are very easy to use and very reliable.

Uniballer
January 6th, 2015, 07:20 AM
I have a Tek 2432A, the 2 channel, 250Mhz version of the 'scope that you have.
No, the 243x and 2440 are 2 channel digital storage/sampling scopes with various bandwidths and sample rates. I used to own a 2430A, which is a 100 MS/s scope with a 150 MHz front end. I believe that the 2432A is a 250 MS/s scope with a 300 MHz front end. But the 2445B that CommodoreKid has is a 4 channel analog 150 MHz scope (little brother to the 2465B).

Mike_Z
January 6th, 2015, 07:21 AM
I use a Tektronix 2230, a 100 Mc dual trace memory scope. I work with a 450 nsec machine cycle 8080 machine. This scope will display any wave form I like, although a double trace on the fastest time is a little dim. I like it, Mike

eeguru
January 6th, 2015, 09:45 AM
How useful is a analog scope these days for digital electronics? A DSO and/or logic analyzer is very useful. But unless you are viewing something that is very uniformly periodic, you might as well be watching Charles In Charge or playing Quake (http://www.lofibucket.com/articles/oscilloscope_quake.html) on that thing.

Chuck(G)
January 6th, 2015, 10:14 AM
How useful is a analog scope these days for digital electronics? A DSO and/or logic analyzer is very useful. But unless you are viewing something that is very uniformly periodic, you might as well be watching Charles In Charge or playing Quake (http://www.lofibucket.com/articles/oscilloscope_quake.html) on that thing.

...or designing a CPU board using an 8080A? :)

eeguru
January 6th, 2015, 12:42 PM
...or designing a CPU board using an 8080A? :)

I wouldn't think an analog scope is very useful for doing that... with a few exceptions of making sure you have a stable clock, dampening over-shoot, and looking for other gross signal integrity errors.

KC9UDX
January 6th, 2015, 01:06 PM
Someone once told me I couldn't properly adjust a Mitsubishi PLG with my Tek 465...

"It has to be a digital storage scope"

CommodoreKid
January 6th, 2015, 02:18 PM
In the past few months, I got along fine with a borrowed Protek P-2640 at 40MHz for checking the CPU board of H89. It wasn't an ideal device for the task, but it got the job done.

More than likely, my first real test for the new 2445B will be helping me figure out whats wrong with my Siemens FDD100-5. Sadly, a snow storm prevented me from safely reaching the only store I know of that sells scope probes.

Chuck(G)
January 6th, 2015, 02:24 PM
I wouldn't think an analog scope is very useful for doing that... with a few exceptions of making sure you have a stable clock, dampening over-shoot, and looking for other gross signal integrity errors.

You'd be surprised at what you can do. For example, ever wonder how one read a PPU P-counter on a CDC 6600 when the console PPU is hung? Grab your Tek 585 and read the pulses as the PPU's turn came by in the barrel. No blinkin' lights on Seymour's baby.

Storage tubes scopes and logic analyzers were nice when they were available, but most of the time they weren't.

Agent Orange
January 6th, 2015, 02:59 PM
How useful is a analog scope these days for digital electronics? A DSO and/or logic analyzer is very useful. But unless you are viewing something that is very uniformly periodic, you might as well be watching Charles In Charge or playing Quake (http://www.lofibucket.com/articles/oscilloscope_quake.html) on that thing.

I suppose it boils down to the task at hand. If I'm observing a circuit(s) comprised of a Lissajous, hysteresis, or various sinusoidal patterns, then I would want an analog scope. My past experience with Motorola type digital oscilloscope/frequency analyzers always left me doing double takes. On the other hand, If you're doing simple TTL levels, timing gates, or working with square waves and/or flip-flops, a digital scope might be the way to go. I see it as personal preference.

Compgeke
January 6th, 2015, 09:06 PM
I know someone who uses an analog Tek (forget what model) for working to determine keyboard protocols on old proprietary keyboards. So far he hasn't had any issues using that.

While I myself have a DSO, make sure you don't end up with one like mine that has the manual settings hidden under menus. I have a Tek TDS684B (1 GHz, 5 Gs/s, 4 channel, etc) and while there's a front panel auto set button you have to go through the menu system to set manual.