ify it that's analogue amplification. And when an H bridge drives a motor w ith a rectangular wave, that's also analogue. And when a comparator amplifi es a sensor's output, ditto. Now I understand. Than you for clarifying.
n.
NT does like to imagine that people have missed the point he was trying to make, when the reality is that he was so far off the point that his comment didn't apply.
-- Bill Sloman, Sydney
Or so NT likes to think. Or - to be more precise - imagines he "thinks".
With NT it's NT's self-image all the way down.
-- Bill Sloman, Sydney
A switching power supply is also an "analog power supply", I can't think of many uses for a "power supply" that accepts 5 volts as input and spits out 0b00000101 in binary code.
thanks for the laugh. And back in the filter you go.
Indeed :-(
Maybe the number of people who are able to operate such scopes has dropped into the noise. Which would not surprise me.
It could be like it is with Hammond tonewheel organs where production stopped in 1975. Their sound is unsurpassed but luckily there are still tons around. Restoration becomes tougher because they are old and most of the more sensitive innards are mechanical parts. I needed a solid 20 hours to get one going again. Now the prices for used ones start to rise. We just sold ours because my wife could not play it anymore due to a wrist injury. In contrast to old pianos it found a buyer almost instantly. Just like it is with Tektronix 2465 scopes.
Well, you can get cheaper ones:
-- Regards, Joerg http://www.analogconsultants.com/
A digital scope can do cool stuff. Adjustable holdoff, bandwidth, and persistance help find patterns in noise. Sometimes FFT helps. Single-shot really helps.
What would be cool is variable-frequency internal trigger, or even some sort of PLL trigger. Triggering external from a signal generator, and signal averaging, can be useful. I have a box with more jitter than I'd expected, and we used a digital scope and a signal generator trigger to discover that a large component of the jitter is synchronous to very close to 1 MHz. The problem now is to figure out why.
That's another way to look at a signal, the spectrum of the jitter. Sort of what HP used to call "modulation domain."
-- John Larkin Highland Technology, Inc lunatic fringe electronics
DSOs can do cool stuff but most of the time you have to know what you are looking for. In most EMI situations that isn't the case. Often clients had noise issues in signals, very faint, and the demodulated signals didn't hold any clues. The noise just wasn't strong enough. This is where an analog scope can excel. When you see the normal fuzz on the trace slightly change in "texture" and then it dawns. "Oh, that looks like Radar noise!".
Maybe use a spectrum analyzer and sniff around the system for a 1MHz source. Especially on power rails but be careful when connecting as that can fry an analyzer input. Needs a series cap and then resistor to ground, and things have to be settled out. _No_ turning on or off while the analyzer is connected.
Triggering from a generator is something any DSO can do. In a pinch use Ch4 or whatever, feed in the generator signal there and trigger on it. Then do vernier control on the frequency and find where the jitter stops "walking". Then you'd know which frequency to hunt and now you can set the spectrum analyzer bandwidth really low for good SNR and fast reaction. Sometimes I even use zero sweep where is shows ampltude changes instantly while doing the "system pat down".
For really tiny noise sources: Use a good shortwave receiver, set to the frequency near 1MHz but 700-800Hz off, in single-sidband mode (SSB). Make sure to pick the correct sideband as there is lower and upper (LSB or USB). Don headphones, connect an EMCO or similar magnetic near field loop and go fishing. This is usually where client engineers think I've gone over the cliff and into voodoo land. But only until the problem is found.
That is extremely hard with a DSO. Easier with analog scopes and a darkened room.
-- Regards, Joerg http://www.analogconsultants.com/
This was assumed to be random, gaussian jitter. But with the scope signal averaging some, and teasing the pulse rate, we can delicately heterodyne what is actually a big periodic jitter contributor.
(note the 50 ps/div sweep. Few analog scopes ever managed that.)
The board has a 40 MHz VCXO locked to a 10 MHz OCXO, and a Zynq SOC with outboard DRAM and an army of PLLs inside. We see this heterodyne jitter at trigger multiples of 1 MHz and 3.2 MHz. Yuk.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
NT protects his self-image from comments that don't reinforce it.
He doesn't learn anything from posts he doesn't read, but he never seems to have learned anything from the posts he responded to so it may be the right strategy for him.
Suits me. He won't respond to this.
-- Bill Sloman, Sydney
Is there RAM bank paging or read/write chunks happening every usec, or maybe every 321nsec? Communication with other boards?
In the end you'll have to find those sources. That is where near field probes and a good receiver or spectrum analyzer come in handy. You'll have to go over the whole board plus all its supply rails. Like crime scene investigators looking for that lone shell casing in the dirt.
-- Regards, Joerg http://www.analogconsultants.com/
I have three Tek analogue scopes: the 475A and 2467 work, and the 466 storage scope doesn't. Fifteen or so years ago, I used to use a 2465A quite a lot, but these days I mostly use DSOs. (*)
I still really like the 246x's triggering.
Cheers
Phil Hobbs
(*) a couple of TDS 784As (1 GHz 4GS/s), a TDS 694C (3 GHz 10 Gs/s), and two 1180x sampling scope mainframes with about 20 plug-ins. Magic.
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
No luck so far! I could cut the jitter at least in half if I can track down that clock leakage.
And I have to confess that that scope HAS a CRT. It's a 50 GHz digital sampling scope with a magnetic deflection (vertical scan!) cathode ray tube.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
I have 20 SD-series plugins on my book shelf. Figure maybe $14K each in the mid 1990s.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Speaking of CRTs.
I just found out that my state does not let you put CRTS or TVs out for trash pickup because of the lead, mercury, etc.
A average TV can have 5 lbs of lead in the glass.
I could not find any free recyclers, they charge a fee.
I dunno Man. Decades ago at my shop in a batch of tradeins I had a TV that had no sync. these came from what subsequently became one of the best shops in town, in fact I worked there for bout eight months and got sick of it. Anyway, EVEY transistor had been removed and checked. I would bet maybe fiv e techs worked on it and they eventually resorted to that.
Well, I was about like 21 and getting GOOD. I found a video waveform on my Tek 422 that was 1.1 volts P-P instead of the 1.0 volts P-P called for on t he print. Open one meg resistor, 12 cents, sold unit for around a hundred b ucks. I think I had the job done in like 45 minutes and had like $25 into p rocuring it. Divvy that up into hours and it is pretty good for like 1982.
I like analog scopes in auto trigger or free run, I use them for DC. In thi ngs like audio and most brownwares you only need to know if a voltage it th ere. It is usually regulated just but now many turns on the SMPS transforme r. (I don't care what whatshisface says, they ARE transformers)
But I would stick it on 20 v/div. or whatever and go through all the power supplies in notime. Audio outputs in am amp, checked in seconds.
If you know how to use it, in troubleshooting an analog scope is the fast t rack. I can check so many things so much faster it is ridiculous.
The few digital/LCD scopes I have seen don't do quite what an old conventio nal CRO does. First of all the CRO responds immediately. Twelve volts, fift een volts, plus and minus sixty volts, you can see it all on the scope imme diately and you also get to see if there is alot of ripple. If that trace i s not sharp and flat you can switch it to AC and see the ripple.
Also, in CRT TVs with reactive scanning (most of them) I could find out if the flyback was bad in less than a minute on most of them. They put out alo t of voltage and were kinda prone to failure, but many people replaced them when they were good. Guess who had to fix it now ? I knew FOR A FACT if it was bad. Within five minutes.
Because of an old style analog CRO type oscilloscope.
Yeah, my CROs got people back to watching their sitcoms and even funnier, t he news, so I guess the term "sillyscope" isn't so far off...
Bottom line is my CROs made my life and lifestyle possible. I think I) was about 14 when i got my first one. It was a HUGE Hickok that I could barely carry and had like a 3" screen. THEN my Uncle who worked for IBM gave me a Tek 310 that had been removed from service. It was the coolest thing I ever had. then he gave me a 561A with a dual timebase plugin so I eventually fi gured out how to work that.
No readouts, no digital, no nothing, if I have to make a choice between a m eter and a scope I will take the scope every time. If I have to I can make a scope act as an ohmmeter. Also an ESR meter for lytics.
Me and scopes is brothers.
So, feed the Z axis of an analog scope with some of your suspect jitter inducers, and look at X/Y plots where X = signal, Y = signal-through-a-delay-line. and you have a fine analog sensor for that effect.
geek even then.
You too ? I was worse. I connected the stereo to the X and Y inputs.
It gets even better, I had an old round tube color TV and connected the pla tes of a tube amp I had to the yoke, well a spare yoke, the one for the TV was laying down in the cabinet - it is required to make the proper high vol tage. And THEN I got even worse, I stated messing with the -Y amps and modu lated the beams.
It was good at parties. You get your X-Y display off the stereo fine, it is monochrome. I had COLOR ! HAHAHA.
I actually thought of making a TV into a scope. there are problems with tha t idea. If you want a horizontal sweep rate of 15 KHz, you gotta pump like a thousand volts into that coil. It is inductive so if you want twice the s peed you are likely to need about twice the voltage. In them old sets even the vertical takes a ton of voltage because it is so inductive.
In the old days almost everything was like that. They did lower the impedan ce of their yokes when we got into solid state, but still they were inducti ve.
In the Maganvox T-991 chassis the horizontal winding still took the usual 1
2.5 uS pulse to effect horizontal sweep. The vertical windings, at those fr equencies for the vertical, were damnear resistive and got fed an actual sa wtooth.You look at the yoke in one of those, it is like "What, is wire like ten bu cks a foot there ?". They abandoned that super low impedance vertical windi ng because it took more power dissipation in the vertical output. With the higher impedance they can drive it with a pulse and then a a controlled rec overy to achieve linearity in the sweep. Sometimes voltage costs more, some times current costs more.
What I never had and I think I will get is a current probe for the scopes. Just a cheap one that works, I don't need that gigahertz shit.
Everything has a purpose. I work on scopes, CROs so I got me a VTVM. I also threw together a 10X probe for it so I can measure 15,000 volts. Those CRO s have CRTs and they have high voltages on well, in a scope kinda both ends of the CRT. Yeah I gotta figure out how to actually calibrate that soon.
Mine are in a Rubbermaid tub under my bench. The ones that don't have the original case are stuffed in a cut-out piece of soft plastic foam.
Do you have the 067-1331-00 Sampling Head Simulator?
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Magnetic deflection produces a much sharper picture, because it can control the aberrations of the electron beam. Electron optics (i.e. electrostatic deflection and focusing) can't do that nearly as well, because it would require a combination of negative and positive lenses, as in optics-optics, and Laplace's equation says that you can't make a negative electron lens.
(A negative lens would require a potential that reached its maximum somewhere away from a boundary, and you can't do that with Laplace's equation--it's known as the 'maximum principle'.)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
I have three Tek analogue scopes: the 475A and 2467 work, and the 466
Which is completely stupid. Lead oxide doesn't leach out of big chunks of glass, and heavy metals don't go anywhere in landfills. The Oklo natural reactor in Gabon went critical about 1.5 billion years back, and ran for a few hundred thousand years, moderated by flowing ground water. The resulting plume of heavy metal fission products has travelled only a few hundred yards in a billion years. The plutonium hasn't even left the individual uranium oxide grains where it was formed.
When I was a kid, I used to build stuff out of parts salvaged from old TVs. Getting rid of the CRTs was fun--I'd stuff them in a big old plastic trash can and shoot them with my slingshot from a safe distance. Hitting the face plate hard enough to break it reduced the tube to fragments of manageable size.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.