_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Well, with my electronics development I am getting into the limits of my old Tektronix 531A... It's also not in a good shape anymore. The trigger mechanism isn't really working anymore, even on digital (TTL) signals, so I can only do time-based measurements. And the time base is not calibrated anymore anyway. Lastly it uses up a LOT of space in my room... [EDIT: not to forget the occasionally puff of smoke coming out of it - at least once so far that I know of...]

So far this hasn't stopped me from using it and getting at least some good qualitative results. But my new 65816 card has a 50MHz oscillator on it, and even though none of the signals actually runs at that speed, I just can't see that signal on my scope. And 10-12.5 MHz static RAM access speed isn't too far away here. And I am still looking forward to finally fix these longstanding problems that make my DRAM-based video card so delicate to handle (depending on chip speed, phase of the moon etc). But for this I also need a decent triggering mechanism.

And as I think of going even further not only with CPLD with FPGA based developments, I thought that it's now time for a new scope. And as I believe in good tools, as they just make your life so much easier, it has to be a good one :-)

André

Some of the new Tektronix 200MHz+ probes are going for more than $450US. Is this worth it?

The 'scope I bought on ebay had included what looks like 2 probes that were originally included with the scope. They're not being sold anymore, and since the scope is "ancient" a price comparison is impossible. And tech back then might not be up to par now...

My question is, does the Nyquist theory (2x oversample) apply to 'scope probe's too? Is it worth upgrading probes?

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65Org16:https://github.com/ElEctric-EyE/verilog-6502

Just open the windows and let the smoke out of the room. Also, think of smoke as a pilot light. If you see smoke it means the power is on.

Knowing that you are in Germany and not knowing what sort of a budget you have to get a new scope, I can't really offer anything other than get the best you can afford. With what you want to do, a 100 MHz unit would, in my opinion, be the minimum to shoot for. As Garth said, probes are equally important, so I guess it becomes a tug-of-war between being able to afford a high-end scope and also afford the high-end probes needed to make the high-end scope produce high-end results.

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

1 last question Garth, because now I know my probes are inadequate trying to measure an 80MHz oscillator, (even though the scope itself can measure 200MHz signals), and you seem to be the most knowledgeable and equipped in this area.

I see an 80MHz sine wave output from a 1/2size 5V powered square wave oscillator. I'm measuring p-pV @+2.5V. Can I rely on that peak to peak reading? I'm using this oscillator to power 3.3V hardware because of this reading. Can I trust it? TIA

_________________
65Org16:https://github.com/ElEctric-EyE/verilog-6502

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

This is a lesson learned. Don't always trust what you see on the 'scope, especially if you know your probes are not up to par which I personally know now thanks to this thread.
I trust the oscillator datasheet more, ( http://www.ecsxtal.com/store/pdf/ecs_2200.pdf ), which says 4.5V p-p. It also says it runs @3.3V optional, but no specs. That's another topic not worth writing about....

Just FYI, at least my scope measured the period correct. Thanks Garth!

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65Org16:https://github.com/ElEctric-EyE/verilog-6502

I meant if one had a 'scope stating 200MHz, would the probes have to be certified @400MHz in order to properly see the 200MHz square wave signal? or did someone say 10X?!

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65Org16:https://github.com/ElEctric-EyE/verilog-6502

The "10x" setting on the probe has to do with the voltage; ie, 1V will show as 0.1V on the screen. However, a square wave has all the odd harmonics (and a little bit of the even harmonics if the duty cycle is not 50%), with amplitude decreasing as you get into higher harmonics. If you have a 20MHz square wave, and you took out all the frequency content above 20MHz, you'd see only a sine wave. If you left the 3rd harmonic in and took out all the frequency content above 60MHz (the 3rd harmonic) without affecting the amplitude or phase of 60MHz and 20MHz, it would look like it's making an effort to be a square wave, but a pretty lousy one. If you could take out everything above 100MHz (the 5th harmonic) without affecting the amplitude or phase of the lower frequency components, it would improve further, but it's not going to look really square until you get to at least 180 or 220MHz (9th or 11th harmonic). So yes, if you want to get a good representation of a square wave at a particular frequency, the oscilloscope should be good to at least ten times the fundamental.

https://en.wikipedia.org/wiki/Square_wa ... e_wave.gif is an animation of the additive synthesis of a square wave with an increasing number of harmonics

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Excellent, I understand. Thanks for taking the time to explain that. Similar principles to audio and waveform generation.

I looked up the probes that came with my scope and found they were 40MHz probes not even made for the scope! I had assumed they were OEM for the 2440. Forgive me, I am abit slow... The correct Tektronix 400MHz probes go for ~$150ea. used which isn't too bad. I'll be ordering them in a few weeks.

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65Org16:https://github.com/ElEctric-EyE/verilog-6502

A bit of a quibble

That's a fine explanation except you leave out the most salient point

The 10x setting presents less capacitance to the ciruit. A byproduct of
doing that (in a simple way) is that it presents 1/10th the voltage to the
scope.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Fair enough.

My point was just that it goes along with (your discussion of) preserving
the higher frequencies.