What bandwidth oscilloscope for 1541 alignment?

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ral-clan
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What bandwidth oscilloscope for 1541 alignment?

Post by ral-clan »

Hi,

If I ever get an oscilloscope, there are probably only a few things I will use it for:

1. 1541 drive alignment
2. calibrating the sound chips on my old Roland Juno 106 sythesizer using the service manual and circuit board test points.
3. checking motherboard signals on old 8-bit computers to diagnose problems (like on a PET motherboard).

What bandwidth oscilloscope do I need? I see there are several very cheap scopes on Amazon, that are hobbyist scopes and are rated at 200kHz.
https://www.amazon.com/Makerfocus-Stora ... cilloscope

I assume 200kHz bandwidth is not enough for working on 8bit computers.

There is also another one rated at 20Mhz. That seems good, but it has no test signal point for calibrating the probes (and I have no generator).
https://www.amazon.com/all-sun-Oscillos ... cilloscope

The reason I am looking at sub-$150 scopes is because I really think I'll only ever use it once in a blue moon for the above purposes, and it seems a waste to buy a $300-$500 scope and just have another piece of equipment that is under-used.
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norm8332
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Re: What bandwidth oscilloscope for 1541 alignment?

Post by norm8332 »

I have one of these and it works great for old computers etc. https://www.ebay.com/itm/272943504784?epid=2181399078 Plus its low cost.
Or you could get a decent used analog scope pretty cheap.
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ral-clan
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Re: What bandwidth oscilloscope for 1541 alignment?

Post by ral-clan »

I have been looking at the Hantek, but my problem is that I run Linux on my computers, and these USB scopes need Windows for their software.

As for the used route, I have had really bad luck with getting used ones that fail shortly after and become useless, so I won't risk it unless I can test before purchase, which precludes ebay, etc....and since I live in a small town, used scopes turn up more rarely than hen's teeth.

I seem to recall that the SAMs 1541 maintenance manual describes a process for alignment that requires a 20Mhz scope....but I cannot find that information to confirm.
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norm8332
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Re: What bandwidth oscilloscope for 1541 alignment?

Post by norm8332 »

There is open source software for Linux..https://github.com/OpenHantek/openhantek I haven't tried it though. Also https://play.google.com/store/apps/deta ... ren.hscope for android. I think there may be more if searched on google.
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Re: What bandwidth oscilloscope for 1541 alignment?

Post by Kakemoms »

Or you can run Qubes OS and have one of the VM templates as Win7. Or vmplayer with a Win image.
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Re: What bandwidth oscilloscope for 1541 alignment?

Post by Floopy »

I'm guessing you might have seen my last post on my 1541 calibration issue. It came down to using an alignment disk or an oscilloscope.
I actually ended up buying an oscilloscope, it's a Tektronix 2230 100Mhz digital oscilloscope. The reason why I bought that model is because first I don't like oscilloscope you hook up to your computer because of various reasons, second they are the exact same machines I used in high school, and third I like the Tektronix brand. The one I got was 110$ shipping included. Important :!: you also need to remember to get an oscilloscope with an external trigger function, if you don't, you won't be able to calibrate the drive at all :!: . \

I do have to point out that I like analog scopes better, but they require calibration and all that mess.

For month I had a DSO138 but it didn't suit my needs.

Hope that helps!
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ral-clan
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Re: What bandwidth oscilloscope for 1541 alignment?

Post by ral-clan »

Kakemoms wrote:Or you can run Qubes OS and have one of the VM templates as Win7. Or vmplayer with a Win image.
I realise running a VM with Windows in it could be a solution to getting one of these USB scopes working within Linux. However, in my case, I specifically run Linux (Lubuntu - light Linux) so I can keep older computers useful. They run great, but running a VM on them is probably too much to ask.
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Re: What bandwidth oscilloscope for 1541 alignment?

Post by ral-clan »

Floopy wrote:I'm guessing you might have seen my last post on my 1541 calibration issue. It came down to using an alignment disk or an oscilloscope.
I actually ended up buying an oscilloscope, it's a Tektronix 2230 100Mhz digital oscilloscope. The reason why I bought that model is because first I don't like oscilloscope you hook up to your computer because of various reasons, second they are the exact same machines I used in high school, and third I like the Tektronix brand. The one I got was 110$ shipping included. Important :!: you also need to remember to get an oscilloscope with an external trigger function, if you don't, you won't be able to calibrate the drive at all :!: . \

I do have to point out that I like analog scopes better, but they require calibration and all that mess.

For month I had a DSO138 but it didn't suit my needs.

Hope that helps!
I actually did not see your thread. I was given two Tektronix T912 analog scopes. But within months both developed problems, which I suspect is failed power supply (but could be more). I have no experience with high voltage electronics, nor playing around with CRTs, and don't feel comfortable putting money and taking a chance trying to repair something I am neither competent nor experienced enough to fix. I need a working scope so I can learn about these things, though.

I have amateur experience working with low voltage digital electronics...and am about at the point where I could start using an oscilloscope to go to the next level.

I totally agree with you about stand-alone scopes, and analog scopes (I like 'em better), but unless I can get a reliable one to learn on, the digital economy scopes seem like a better bet.
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Re: What bandwidth oscilloscope for 1541 alignment?

Post by Floopy »

That's okay, it was just me trying to figure out how to realign my drive in my last post.
I'm going to try a realignment as soon as my leads come in the mail because so far I have no way of connecting anything to my scope.
Anyway to get back on subject, it will all come down to how much time and money you want to invest. With me It's a valuable asset and I really needed one.

If I lived in Canada I would certainly buy two broken scopes :mrgreen:

This is totally of topic but if you get a high enough frequency scope you can play oscilloscope music on it. I know this isn't a thing your wanting to do, but I thought I could point that out.
-Floopy
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Re: What bandwidth oscilloscope for 1541 alignment?

Post by eslapion »

ral-clan wrote:I assume 200kHz bandwidth is not enough for working on 8bit computers.
The highest frequency signal I have had to deal with relating to 8 bit Commodore computers is the color clock of PAL C64 and that's 17.7344MHz. Since it's a square wave signal, getting a correct read on it requires a scope with a bandwidth at least 3 times higher.

When it comes to the 1541 alignment, you want to know the highest bitrate of the R/W head and that's set by a counter which can be set from 13 to 16 and it is runs at 16MHz. In other words, this 16 MHz source can be divided from 13 to 16. When it's divided by 13, the result is 1.2308MHz. This frequency is further divided by 4 and this gives 307.692 KHz.

Since it takes 1/5 of a second to get a complete track revolution, you can store a maximum of 61538 bits of data on a track with the highest density or 7692 bytes. This doesn't take into account the necessity to use GCR encoding and sector syncs which shaves off about 25%.
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Re: What bandwidth oscilloscope for 1541 alignment?

Post by groepaz »

200kHz is barely enough to work with audio.... useless for anything else :=)
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Re: What bandwidth oscilloscope for 1541 alignment?

Post by eslapion »

I am about to sell my own TDS1002. It comes with communications module TDS2CMA with serial, parallel and GPIB port.

  • Bandwidth: 60 MHz
    Analog Channels: 2
    Max Sample Rate: 1 GS/s
    Form Factor: Benchtop

Asking 400$CAD. Yes, I know they sell them cheaper on eBay but they don't come with the TDS2CMA which usually sells for 300$ by itself.

All tested, working and calibrated. (calibration is NOT NIST traceable)

Promotional material and specifications: https://www.upc.edu/sct/documents_equip ... id-533.pdf

User manual: https://people.ece.cornell.edu/land/cou ... ds1002.pdf

General information page and photos (back photo shows TDS2CMA module installed): https://www.allaboutcircuits.com/test-m ... s-tds1002/

The power cost is compatible with north american electrical outlets only but the oscilloscope supports European (120-240Vac) voltages so you only need to buy a standard computer power cord for your country if you want to use it in Europe/UK.
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