problems with used oscilloscope

Discussion in 'General Electronics Chat' started by lokeycmos, Nov 30, 2011.

  1. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
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    this is a scope i picked up on craigslist for 30$. having some issues with the screen. not sure if its something wrong or if im not using it correctly. here is a link to a video i made about it.

    http://www.youtube.com/watch?v=LD57nUtVhWw

    i dont have a probe for it. i went to radio shack and bought a bnc to coax F connector then cut off and stripped back a piece of tv coax cable for a probe. im welcome to input and advice. remember, this is more of a tinker toy for me while i learn how to use one. ty

    tektronix
    Model 564 Tektronix storage scope
    With 3B4 timebase
    3A1 Dual trace Amp
     
  2. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    You are using it in storage mode, that's why the screen looks like that.
     
  3. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
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    could you please explain how that is suppossed to work? how is it useful? what about the bleeding later in the video?
     
  4. MrChips

    Moderator

    Oct 2, 2009
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    The bleeding is normal. That is the way the storage function works.
    I'll explain it later.

    For now ignore the storage function. Just use it in normal mode.

    I have posted some photos here so readers get a good idea of the Tektronix Type 564 scope we are discussing.


    [​IMG]

    [​IMG]

    [​IMG]


    [​IMG]
     
    Last edited: Dec 2, 2011
  5. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Youi set it to single sweep and it records and displays the wave sweep. Before the digi age, that was the only waveform storage.
     
  6. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
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    a couple pics. my homemade probe. how does the 'calibrate' work?
     
  7. Jotto

    Member

    Apr 1, 2011
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    All calibration on the scope should be fully clockwise. I am not sure about your scope, but you should have a 5vdc square wave that will tell you your probe is working properly.

    Mine says "probe comp". Your probe will hook there and you should see a 5 vdc signal. Its just a loop to hook to on the front of the scope.

    It could be a 1 vdc peak to peak also.

    The cal I am talking about is the red knobs on the volt/div and time/div. They go all the way clockwise and click when fully clockwise. I see the cal adjustment below the volt/div and that is probably an adjustment you can use if the scope is out of adjustment. I have never used that scope so you will need a standard to adjust that, and by standard I mean something PMEL would use to cal your complete scope to the Standards and Measurements.
     
    Last edited: Dec 1, 2011
  8. MrChips

    Moderator

    Oct 2, 2009
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    Set CALIBRATOR to 5V

    Set CH1 VOLTS/DIV to 5V

    Connect CH1 probe to CALIBRATOR, CAL OUT

    You should be able to observe a square wave that has a height of 1 division.
     
  9. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
    432
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    could you please explain the storage function? to me it looks wrong, but i guess thats how it works. the first thing i thought when i heard 'storage scope' was a memory. but obviously its tube and transistor powered so it cant store it digitally.
     
  10. MrChips

    Moderator

    Oct 2, 2009
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    Ok. What is a storage oscilloscope?

    Let us back up for a moment. The scope that you have is an analog one, using a cathode ray tube (CRT), like in the old TV sets before the whole world went digital.

    The CRT consists of a beam of electrons, much like a laser pointer. The electrons are aimed at the glass screen that is coated with a phoshpor (a chemical that glows when electrons hit it). The electron beam is steered at the screen using a pair of high voltage plates. Two plates steer the bean vertically (CH1 & CH2 Amplifier) and another two plates steer the beam horizontally (TIME BASE).

    As the beam is swept across the screen you will see a dot on the screen. If the dot is moved quickly and repeatedly across the screen, it would appear as a line. The line does not last for long. How long it lasts for is called persistence.

    In order to see a waveform, we have to sweep the beam across the screen repeatedly with the same pattern. Hence the voltage waveform must be repetitive, giving the same information over and over again.

    The problem with this is that if a pulse occurs only once, we may see a blip on the screen and then it is gone.

    The storage scope is a way of painting a single sweep on the screen and holding it there. This is done with a special electron flood beam that illuminates the entire screen. The picture on the screen will eventually leak out and go away. You can control how long the picture is held on the screen by adjusting the persistence time.

    Think of it as a wet paint brush across the screen. Eventually the paint runs or bleeds. This is the bleeding effect you see and this is normal for this type of storage scope.

    In summary, use the scope in non-store mode most of the time. Use storage for slow repetition rate or one-shot signals.

    Check out:

    http://en.wikipedia.org/wiki/Oscilloscope_types
     
    Last edited: Dec 1, 2011
  11. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
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    ok i just tried out the calibrate. it is a 5v squarewave. i set the v/div to 5v. i dead centered the bottom of the signal (0v) with the center of the gratuical(i think its called). it is a tiny bit off. the top of the wave is just a hair above the 1st line. its probly only in the mV range, but how to i adjust so the top of the waveform lines up exactly on the first horizontal line(5v)?
     
  12. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
    432
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    could someone please explain triggering? im having a tough time grasping the concept. im trying to teach my self. ive been on google and youtube. what would be a common sinereo i would need/use this?
     
  13. Adjuster

    Well-Known Member

    Dec 26, 2010
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    Scenario? Any time that you want the trace to begin* when a vertical input or auxiliary triggering input has a certain level and direction of variation. *For an analogue scope like yours this will normally mean the horizontal position at the beginning time of the trace, conventionally at the left-hand end. Digital scopes can effectively time-shift this event along the trace, but let's not go there for now.

    Some analogue scopes do support delayed triggering, which means that you can look forward in time on an expanded scale after the trigger event, but you cannot look backward: the latter requires electronic storage.

    The most common use of the triggering function is with a repetitive signal like a sine-wave, when appropriate use of the trigger and other controls can make the trace appear stationary on the screen, instead of moving about horizontally or even appearing as a blur.

    For single-shot events, such as you might record with the storage function on your model, the trigger decides when the recording will begin.
     
  14. MrChips

    Moderator

    Oct 2, 2009
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    The triggering section is the most important section of the scope. This is where most new comers have difficulty understanding. Take the time to fully understand this part and you're on your way to become a pro.
     
    Last edited: Dec 2, 2011
  15. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
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    i dont see any knobs to calibrate the screen to the 5v squarewave. seems slightly off...
     
  16. Adjuster

    Well-Known Member

    Dec 26, 2010
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    That is some instrument you have there! As far as I can tell, it was built no later than 1968, and so is likely over 40 years old. You might therefore expect that its performance may not be quite up to its new specifications. http://http://www.barrytech.com/tektronix/vintage/tek564.html

    There may or may not be a user-accessible amplitude cal. trim, but you should check that the red variable volts/div knobs are turned to their "calibrated" positions - they probably click in. One of the chief uses of the calibrator is to check probe set-up adjustments.

    Treat the old contraption with care, because it may not be practicable to do much in the way of repairs to it now: it contains devices like electron tubes and "nuvistors" (sub-miniature electron tubes) which are long obsolete. It is quite a chunk of hardware though, very well made and probably costing many hundreds of dollars back in the day, when money bought rather more than it does now.
     
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