I keep a Dumont 274 oscilloscope next to my tube amplifier in the living room, as a conversation piece. I don't know the original owner, but it must have been proud of this instrument because it has been well cared off and it still looks great despite the late '40 build date. The italian importer added a nice metal plate on the top with contact informations, and also supplied the Italian translation of the schematic diagram. I guess that it was deemed useful back then. The user manual is quite unusual to me, because it is basically a crash course on how to troubleshoot a radio set. This "free added value" was mentioned on the magazine advertisement. Maybe this was a common practice to help selling oscilloscopes to small repair shops or HAM radio operators. The point of this advertisement is that a oscilloscope is useful to repair a radio, I guess that at that time some repairmans did not feel the need to have one. The schematic diagram looks ancient, maybe a pre-war design. I wonder if it would be worthwile to restore this device and turn it on for fun. It seems that nobody tried to turn it on for the last 40 years. I attach a low-res copy of the user manual.
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As somebody who knows that era I can assure you both the advertisement and the oscilloscope are ORIGINAL to the ,40 era .
You have to realize that in the ,40,s WW2 occurred everything went on war production not on the public or non contributing businesses to the war effort.
As a result late 1930,s designs prevailed for a while and 200kHz was pretty good for general audio projects of the day .
HAM radio was banned in the UK ---and Germany for obvious reasons ( check out the radio vans sent round with directional radio signal tracing to capture spies) I don't know if Italy banned it , in any case due to the low frequency response it wouldn't even have been any good for looking at an IF trace as most in that era were=
455kHz/465kHz or around that frequency (pre-war there were some below this)
Of course this did not apply to the armed forces like the UK REME who got much higher spec equipment used to test and repair communications receivers/ radar /etc .
After the war innovations secretly used in WW2 like tube designs were used in early ,50,s radios .
If you have a scope in good condition of that era it will certainly be worth money to collectors or a museum .
You have to realize that in the ,40,s WW2 occurred everything went on war production not on the public or non contributing businesses to the war effort.
As a result late 1930,s designs prevailed for a while and 200kHz was pretty good for general audio projects of the day .
HAM radio was banned in the UK ---and Germany for obvious reasons ( check out the radio vans sent round with directional radio signal tracing to capture spies) I don't know if Italy banned it , in any case due to the low frequency response it wouldn't even have been any good for looking at an IF trace as most in that era were=
455kHz/465kHz or around that frequency (pre-war there were some below this)
Of course this did not apply to the armed forces like the UK REME who got much higher spec equipment used to test and repair communications receivers/ radar /etc .
After the war innovations secretly used in WW2 like tube designs were used in early ,50,s radios .
If you have a scope in good condition of that era it will certainly be worth money to collectors or a museum .
That's still true today!Duncan2 said:
My Rigol DS 1054Z 'scope has 7 bits vertical resolution and 50 MHz bandwidth; that's only 128 steps in the vertical direction, making audio waveforms jaggy and unpleasant to look at.
Personally, I'm only interested in audio frequency electronics, so I would much rather have a 'scope with 12 bits of vertical resolution and only 200 kHz bandwidth (heck, 100 kHz would be ample).
But nobody sells anything like that, probably because there would be very little market for it nowadays, in the era of all-digital, all the time. Almost everyone who buys a 'scope nowadays wants to look at digital signals.
-Gnobuddy
I had a DuMont rackmount scope in the '60s. It was really solid and had a lot of tubes. It arrived missing one that turned out to be a ballast for the filaments. Worked OK. I believe it was a recurrent sweep scope, something unknown today. It would sync on the incoming waveform regardless of its frequency. No real timebase.
A decent soundcard + attenuator or interface box + software will get you what you just asked for. Probably for not much investment at all.
It's a good suggestion, and one I did look into quite a bit. There were four main reasons why I didn't take that route:1audio said:
1) The interface box. I want to use this to look at vacuum tube guitar amps and preamps, so up to maybe 450 volts DC, with the biggest AC voltages swinging nearly twice that, say 800 volts peak-to-peak. The interface box would have to provide galvanic isolation, very high input impedance (say 10 megohms), and the ability to look at everything from 10 mV AC signals to 800 volts peak-to-peak AC signals. So low-noise circuitry, overvoltage protection, and a lot of switchable ranges would be required.
This didn't seem like a trivially simple thing to design or build, so it posed a significant obstacle. In th end, I decided I didn't want my measurement tool to turn into yet another big project - I wanted something I could take out of the box and use for the pile of projects I already had waiting in the queue!
2) Concern over the welfare of the PC. This is related to item (1), i.e., if I didn't get the design of the interface box quite right, I could end up frying my PC or laptop, which I can't afford to do. (I could also end up frying myself, which I also didn't relish the thought of too much).
3) The software: I don't use Windows in my personal life, and haven't since 2001. I use Linux, and haven't been able to find any sound card oscilloscope software for Linux that is still current - the few offerings I found were ancient, and won't work on any modern version of Linux.
Why not get Windows, then? I do use it now and then (when forced to) at work, and have installed it on PC hardware for friends and co-workers at their request. As far as I can see, Windows 10 has completed the transition from what was once an operating system to what is now a gigantic collection of Microsoft spyware that takes over your entire computer.
4) The physical size: a laptop is way bigger than a modern oscilloscope, and a PC + monitor is even bigger. My cramped workbench doesn't offer much room for either (I have my Rigol tucked on top of a shelf I build over the workbench.)
I did find a solution that addresses items 1 & 2 well, and item 3 partially; a Canadian company called Syscomp used to make a USB 'scope called the CircuitGear Mini for educational use: CircuitGear Mini – Syscomp Electronic Design
When I discovered these, they were selling for something like $60 USD (about $75 Canadian at the time). It has eleven-bit vertical resolution and a 200kHz bandwidth. Perfect, so I bought one. What I didn't know at the time was that the company founder had recently passed away, and Syscomp itself was already in shut-down mode. The website is still up, but the company appears to be quite dead now; all their products are listed as "out of stock and unavailable". Pity, they had some good products at great prices.
My CircuitGear Mini does work on Linux, and I have used it for some measurements. However, one of the most exciting features - full two-channel complex (magnitude and phase) frequency response measurements - turns out to be unable to measure things like higher-Q filters (guitar speaker emulation filters), possibly because the software steps the frequency too fast, smearing the response. The software is open-source, but with Syscomp now moribund, I'd have to fix it myself - which I could probably do, but haven't felt like tackling yet another project!
-Gnobuddy
All valid points. The Syscomp looks like a neat gadget. Similar to Digilent but cheaper. Its a shame it came to an end. I wonder if the software could mate up with this guys projects- PC USB scope project.
A 'scope was VERY expensive until Heath organized WWII surplus into kits.
And in my own experience: the #1 reason to own a 'scope is to drop acid and watch the patterns. (Actually: to keep trippy hall-mates occupied.) I've always had one around and almost never used it in repairs. You get a lot of squiggles but what do they mean? You can work it out, but often the same brain-power on other symptoms gets an answer without an enormous box on the bench.
That box and schematic is "SAME" as mine except clearly post-WWII. Mine was 5-pin tubes ('57?) not the octal 6AC7 (a WWII hero). While yours is single-side drive, your CRT has all 4 pins; mine didn't.
Its a pity you don't have the space but most high quality old analogue scopes can easily do what you want with a much better resolution .
I would never part with my CRT analogue Tektronix -2445A , never let me down after many decades .
You can still buy old scopes that are ex government/industrial.
Absolutely agree on Windows proved it to myself and others time and time again.
I have Manjaro installed on two PC,s but its starting to get bloated even with the minimilist version but a "new " kid is on the block (actually a replacement for an old system called Endeavour ,download the ISO and burnt to DVD , just about to install it , not far off Arch ,nearer than Manjaro---you decide whats installed.
I would never part with my CRT analogue Tektronix -2445A , never let me down after many decades .
You can still buy old scopes that are ex government/industrial.
Absolutely agree on Windows proved it to myself and others time and time again.
I have Manjaro installed on two PC,s but its starting to get bloated even with the minimilist version but a "new " kid is on the block (actually a replacement for an old system called Endeavour ,download the ISO and burnt to DVD , just about to install it , not far off Arch ,nearer than Manjaro---you decide whats installed.
Considering resolution the 24bit soundcard with approx 20bits valid outperforms any analogue scope. You could build your own HV-Adapter based on an oscilloskope probe and some small interface box. There is some really nice professional scope sw that works under linux/wine
FFT Analysator Software Freeware > Visualisierung und Auswertung, spectrum analyzer software.
This is for free as a support for their usb interfaces for measurement applications but works with any soundcard.
On the other hand, on my opion most repair jobs are done effectively using a DVM. And if curve shape matters - the resolution of my rigol is ok for me.
FFT Analysator Software Freeware > Visualisierung und Auswertung, spectrum analyzer software.
This is for free as a support for their usb interfaces for measurement applications but works with any soundcard.
On the other hand, on my opion most repair jobs are done effectively using a DVM. And if curve shape matters - the resolution of my rigol is ok for me.
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I used and loved Tektronix 'scopes of that era in college. After I moved to Canada some years ago, I looked for surplus analogue 'scopes, and I found thoroughly used Tektronix ones going for $600 CAD - while the brand new 4-channel Rigol could be had for about $450 with my educational discount.
I agree about some of the nicer qualities of analogue/crt. To this day, I see some truly nasty-looking jagged fonts on some LCD PC monitors - I never saw anything as unpleasant in the CRT era, where the beam spot size (and intensity profile fading to the edges of the spot) automatically and gently smoothed the edges of all fonts.
Of course modern digital 'scopes have lots of really nice qualities, too. Automated frequency measurement of the incoming audio signal is one of the nicest. That was a tedious measurement on an analogue 'scope, and you needed a calculator too, to go from waveform period to frequency!
-Gnobuddy
Thanks for the link!
Can you point the software at any soundcard seen by the operating system, then?
Also, it's called FFT Analyzer - does it actually also work like an oscilloscope, to look at waveforms?
Personally, I don't think the hardware interface is quite that simple a project, at least for me. I bought a couple of 100x, 1 kV scope probes that help solve the scariest problem, but ideally, I would like galvanic isolation (no shared ground) between guitar amp under test and computer, along with a 100 kHz bandwidth, and no added distortion from the optocoupler or whatever is used for that galvanic isolation.
I find the Rigol's 7-bit vertical resolution usable, but very ugly. Much like the programming language Perl, which I used to use a fair bit about twenty years ago. It was powerful, but very ugly.
When hunting for the beginnings of clipping in a (tube) guitar preamp signal, I often cannot tell if the signal is just starting to clip, or it's just the stair-step Rigol waveform that's flat-topped because of the utterly crappy vertical resolution. Every sine wave signal looks like the peaks are clipped when you only have 7 bits of resolution!
On the plus side, the Rigol has an FFT function, which can also tell you when clipping starts.
But I agree with PRR - having any kind of affordable 'scope is a luxury, one I didn't have during the years when I was most active at designing and building electronics. Now I have both LTSpice and a 'scope, both wonderful tools, but I design and build much less stuff. Particularly in the last few months, since COVID-19 took control of our world, and our primary focus became trying not to get infected and killed by an invisibly small virus...
-Gnobuddy
To answer your question - there is an oscilloscope in this sw.
I had a short look at it as a replacement for ARTA. As I could not discover a menue for frequency response measurement I dropped that soon.
Concerning the luxury - I do repairs on a regular basis and my experience is that you trace most errors fastest by using DVM to measure DC-biases first - and not to google for the service manual but do a visual inspection first. Reading the circuit diagram is not the first step to go - and this is no snobbery.
I had a short look at it as a replacement for ARTA. As I could not discover a menue for frequency response measurement I dropped that soon.
Concerning the luxury - I do repairs on a regular basis and my experience is that you trace most errors fastest by using DVM to measure DC-biases first - and not to google for the service manual but do a visual inspection first. Reading the circuit diagram is not the first step to go - and this is no snobbery.
Show them this.
DIY $20 Oscilloscope - YouTube
~$25, build the kit in 2 hours. 200kHz analog bandwidth, 12bit vertical resolution, hand held.
But this is OT as everything past post #14
George
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Joined 2009
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FYI - if affordability is the main issue, they’re almost giving these away on ePay. Mine arrived last week, haven’t unwrapped it yet though. At these pricess I can put one in every amplifier chassis....
Specifications:
Maximum Real-time Sampling Rate: 1Msps
Accuracy: 12Bit
Sampling Buffer Depth: 1024 bytes
Analog Bandwidth: 0-200KHz
Vertical Sensitivity: 10mV / Div - 5V / Div (1-2-5 progressive manner)
Input Impedance: 1MΩ
Maximum Input Voltage: 50Vpp (1: 1 probe), 400Vpp (10: 1 probe)
Coupling Modes: DC / AC / GND
The Horizontal Time Base Range: 10μs / Div - 50s / Div (1-2-5 progressive manner)
Supply Voltage: DC 9V
PCB Size: 117 * 76mm / 4.6 * 3in
Screen Size: 52 * 40mm / 2 * 1.57in
Weight: 132g
Note: the power supply is 9V 1A with 4.0x1.7mm DC connector (not including)
Specifications:
Maximum Real-time Sampling Rate: 1Msps
Accuracy: 12Bit
Sampling Buffer Depth: 1024 bytes
Analog Bandwidth: 0-200KHz
Vertical Sensitivity: 10mV / Div - 5V / Div (1-2-5 progressive manner)
Input Impedance: 1MΩ
Maximum Input Voltage: 50Vpp (1: 1 probe), 400Vpp (10: 1 probe)
Coupling Modes: DC / AC / GND
The Horizontal Time Base Range: 10μs / Div - 50s / Div (1-2-5 progressive manner)
Supply Voltage: DC 9V
PCB Size: 117 * 76mm / 4.6 * 3in
Screen Size: 52 * 40mm / 2 * 1.57in
Weight: 132g
Note: the power supply is 9V 1A with 4.0x1.7mm DC connector (not including)
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Click "English" top left; Software; FFT Spectrum Analyzer Freeware;
"...you can use the Sound Card of your PC.. or you can use a specific external hardware ....
"Windows 9x,ME,2k,XP,NT,Server,Vista,7,8/10.
"The 2011-2012 version runs on Linux by means of wine utility.
" Oscilloscope (dual channel, xy, time division, trigger);
Spectrum Analyzer
Wave-form generator
Frequency meter
Volt meter
Filtering
Support for 8/16/24 bit soundcard by means of API calls;
......................................"
Thanks!PRR said:
So the pros and cons stack up a bit like this:
Con: needs an interface box
Con: only old versions run on Linux, and not directly, only via Wine.
Con: doesn't do frequency response plots
Neutral: probably only 20 kHz bandwidth (with my internal integrated sound-card); adequate for guitar amplifier measurements, as nothing above 10 kHz matters in a guitar amplifier.
Pro: better vertical resolution than my Rigol 'scope.
-Gnobuddy
You may try Visual Analyser as a scope:
Visual Analyser details
It seems that the author has resumed the work on this program, there are newer Beta Versions than 2014 Visual Analyser
You can do frequency response plots using white noise btw.
However, for measurements in frequency domain, I would prefer ARTA or REW, if you have to use the soundcard. These programs have so much functionality.
Visual Analyser details
It seems that the author has resumed the work on this program, there are newer Beta Versions than 2014 Visual Analyser
You can do frequency response plots using white noise btw.
However, for measurements in frequency domain, I would prefer ARTA or REW, if you have to use the soundcard. These programs have so much functionality.
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