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Heathkit oscilloscope FIXED !!

Discussion in 'Electronic Basics' started by Ivan Vegvary, Nov 27, 2012.

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  1. Ivan Vegvary

    Ivan Vegvary Guest

    Heathkit IO-18

    Thanks everyone for the help/advice in fixing the above. Problem was the 1V2 tube. Saw a deal on E-Bay (5 tubes for $12). Took a chance. They all seemed brand new (with boxes) and all tested well in the scope. Now I don't know what to do with the other 4 leftovers.
    Now I need something to use the scope on. Are there any simple signal generators (on the web) that can be built from scratch? Can I watch some low frequency outputs from the handful of 555 timers and other IC's I have on hand? I do have a breadboard and a good stock of oddball resistors and capacitors.

    Started a new post because the previous one got too ugly.

    Thanks again.

    Ivan Vegvary
  2. Jon Kirwan

    Jon Kirwan Guest

    I can provide a pre-programmed TI LaunchPad (it cost me
    $4.30, so I don't care at all giving it away) that would use
    a crystal to provide a variety of frequencies for you.
    Voltages would be 0 to +3.6V. It would take me only a few
    moments to write up the code for it. I think we live nearby
    so I could drive it over and would be glad to do that. You'd
    get good-accuracy signals. Just let me know what you'd like
    to have as signal outputs.

  3. JW

    JW Guest

    You might take a look at the Exar XR-8038 waveform generator chip. While
    it's been out of production for a long time, they can still be found on
    Ebay for less than $5.
  4. JW

    JW Guest

    There's some links here that might be of use.
  5. Bob Masta

    Bob Masta Guest

    You might want to have a look at my Daqarta software, which
    uses the sound card in a Windows system to generate signals
    (among many other things). As a signal generator it is
    absolutely *free*: After the 30-session/30-day trial period
    expires, only the signal *inputs* stop working, but the
    *outputs* and most other stuff keep working as before.

    The Daqarta generator allows all kinds of waveforms (Sine,
    Triangle, Ramp, Square, Biphasic Pulse, Arbitrary, Play
    recording, uniform White noise, Gaussian, Pink, or
    Band-limited noise) plus modulation schemes (Burst, AM. FM.
    PM/PWM, Sweep), with 4 independent "streams" per stereo
    output channel that can be added in arbitrary proportions.
    Or you can use streams to modulate other streams.

    You can also see the signal you are generating on the
    display, with lots of triggering options, so you can compare
    to what your Heathkit shows you.

    The downside of using a sound card for this is that they are
    AC-coupled, so tops of low-freq square waves droop. Also,
    sound cards are limited to the "audio range", though modern
    cards (even some cheapies built into inexpensive laptops)
    can now sample at 192000 Hz and are thus useful at up to
    (nominally) 96000 Hz.

    Best regards,

    Bob Masta

    DAQARTA v7.10
    Data AcQuisition And Real-Time Analysis
    Scope, Spectrum, Spectrogram, Sound Level Meter
    Frequency Counter, Pitch Track, Pitch-to-MIDI
    FREE Signal Generator, DaqMusic generator
    Science with your sound card!
  6. I was going to say that, but I couldn't remember if those cheap scopes
    (and I had one once, $5.00 at a local ham club auction about 1973, really
    heavy, and barely able to handle audio) had a horizontal input.

    There are lots of things one can do with one of those, if nothing else
    just to get an idea of an oscilliscope. I got my five dollars worth, if
    nothing else, learning it wasn't that useful (but it was fun at the time).
    Until one can see a need for a scope, it's silly to spend much money, and
    difficult to determine what's useful. A scope like this gives some play
    time to explore it, even if it is much simpler than will be useful. Just
    don't spend a lot of money on them.
    Those were popular in the seventies, as triggered (to some extent) scopes
    came along that were within reach money wise. Suddenly they were almost
    in sight, so might as well get some of the function from the old scope.
    It also helped that one could use semiconductor devices, so a small board
    could be made to fit in the old scope.

    Of course there are still limitations, AC coupling, very little frequency
    response, but fun.

    Soon after, I had the use of a Tektronix scope, the 454? The 100 or
    150MHz one that was more horizontal than vertical (sizewise) and was solid
    state except for a nuvistor front end. A kid at school saw it, and told
    others it was a "multi-color" scope, I'm not sure where he got that,
    except besides the trace, it actually had a graticule that lit up.
    There was the time I hooked a VTVM to a tv set, the transformerless kind.
    I knew better, just simply forgot at that moment. The insulation on the
    ground lead proceeded to burn up, the actual wire holding. I'm surprised
    a fuse didn't blow. I still have that 410B, it was never hurt other than
    no insulation on the ground lead.

    If we don't admit our stupidity of being young, it won't help the
    beginners in making their own mistakes.

  7. Bob Masta

    Bob Masta Guest

    On Wed, 28 Nov 2012 12:13:32 -0600, Tim Wescott

    Not ground-referenced? I think 30 years ago (if not today
    as well) the amp outputs of most "home stereo" receivers
    were ground referenced. Some cheapie units (and probably
    most car stereo units) used bridge mode, I imagine.

    But I'd guess the problem was that the scope *was* ground
    referenced, and that trying to do a differential measurement
    with a single-ended scope just shorted one channel of the
    amp to ground. (Been there, done that!)

    Best regards,

    Bob Masta

    DAQARTA v7.10
    Data AcQuisition And Real-Time Analysis
    Scope, Spectrum, Spectrogram, Sound Level Meter
    Frequency Counter, Pitch Track, Pitch-to-MIDI
    FREE Signal Generator, DaqMusic generator
    Science with your sound card!
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