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Beginning Oscilloscope Question

Discussion in 'Electronic Basics' started by [email protected], May 5, 2007.

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  1. Guest

    I just received an oscilloscope I bought off eBay. I'm trying to test
    it but can't seem to get any vertical deflection. I setup a little LED
    flasher with a 16F88 and put it in INTRC+ClkOut. When I measure the
    clock frequency with my multimeter I get 62kHz. But I can't get the
    scope to show any deflection. I was expecting to get a square wave
    with a peak voltage of 5v.

    I don't have the manual. It's a Tektronix 2336 100mhz. Any ideas?
     
  2. redbelly

    redbelly Guest

    Just taking a guess here, is there a knob that is set to "ground" or
    "gnd" instead of DC or AC?

    Regards,

    Mark
     
  3. Guest

    I've tried both channels on AC and DC.
     
  4. Bob Myers

    Bob Myers Guest

    You put in in WHERE? On the images I've been able to find
    of the 2336, there doesn't seem to be any such input.


    Bob M.
     
  5. Phil Allison

    Phil Allison Guest

    <>

    ** Groper Alert !


    ** What ** ARE ** you seeing on the screen??

    Nothing at all ?



    ........ Phil
     
  6. Forget the probes. Just touch the input pin with a small screwdriver while
    you are holding the metal shaft. You should get a ragged wave.
     
  7. Guest


    Poor wording on my part. I was (am) just using a little PIC program to
    generate a flashing LED so I know the circuit is working. I put the
    PIC16F88 into the INTRC+ClkOut mode. Which, if my understanding is
    correct, outputs the internal oscillator clock signal on a I/O pin.
    PIC program:

    org 0
    goto main
    org 0x100
    main
    bsf STATUS, RP0
    movlw 0x0
    movwf 0x5
    bcf STATUS, RP0
    loop_3 movlw 0x2
    movwf 0x5
    loop decfsz 0x20, f
    goto loop
    movlw 0x0
    movwf 0x5
    loop_2 decfsz 0x20, f
    goto loop_2
    goto loop_3

    When I turn the circuit on the LED flashes as expected. And, if I use
    the frequency counter on my multimeter between the clock output pin
    (on the PIC) and ground I get about a 60khz reading. However, if I
    attempt to sample the same signal with the scope I get nothing but the
    horizontal sweep. I've tried different combinations of V/div and Time/
    Div.

    The only things I've been able to make the scope do is slow the
    h.sweep down enough to see the scrolling dot. I've even tried to see
    if I could get a DC offset with a battery, nothing.
     
  8. He's referring to the way he set up the PIC. He is using the internal
    oscillator block and having it simultaneously present the instruction clock
    on an output pin. He is trying to see that clock signal.
     
  9. Ok, it's triggering then. Have you made sure that the probe is switched to
    the X1 or X10 positions? Do like Homer said to make sure it's not the
    probe. Outside of something basic like that, it doesn't sound too good, but
    I would think it kinda odd that both channels would be dead.
     
  10. Guest

    I've tried both 1x and 10x on two different probes (although I
    purchased them from the same person on ebay at the same time). Messing
    with various settings I've gotten it to the point of having the screen
    blank unless I touch something metal, and then it will do a horizontal
    sweep. But I've still not been able to get it to show any vertical
    deflection.

    The first time I powered it on, both channels were displayed on the
    screen and I was able to use the V.Position knobs to move the
    individual traces around, ever since first turning it on I haven't
    even been able to get that much, and the V.position knobs do nothing
    now. I'm wondering if something is wrong with the vertical circuit.
     
  11. You've set both channels to max sensitivity?
     
  12. Eeyore

    Eeyore Guest

    Do you get any deflection when you probe the +5V ?

    Graham
     

  13. The user manual is on the Tektronix website. http://www.tek.com/
    Learn how to use a search engine.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  14. Guest

    You've set both channels to max sensitivity?

    Yes, same thing.
    You must be better than I am at it. I've spent a lot of time searching
    through their Manual Finder section and have not found a manual for
    the 2336. I found a service manual for a 2236, but on a different site.
     
  15. You do realize taht ebay isn't the best source of quality(i.e. working)
    equipment? Its probably the largest source of con arists and scammers that
    exist.
     
  16. Mike

    Mike Guest

    I couldn't find it there either, but you can get it at http://bama.sbc.edu/tektroni.htm
    The site is very slow and hard to get in, but I did finally get the manual.
    You might try here also http://dion.swamp.dk/tek2236.html

    Mike

    "As we survey all the evidence, the thought insistently
    arises that some supernatural agency - or, rather,
    Agency - must be involved. Is it possible that suddenly,
    without intending to, we have stumbled upon scientific
    proof of the existence of a Supreme Being? Was it God
    who stepped in and so providentially crafted the
    cosmos for our benefit?"
    George Greenstein - Astrophysicist
     
  17. Guest

    Yes, I found the manual for the 2236, unfortunately I have the 2336. I
    tried the baseline test procedures from the 2236 manual as much as I
    could. I don't seem to get the 1khz square wave when I test the
    calibration output on the device.
     
  18. Ok Jon, no need to rub salt in the wound. :) E-bay is what it is, a cross
    section of society; the good and the bad. I've gotten some great deals on
    E-bay, but I've been rooked a time or two as well. Could be that the scope
    worked perfectly and that it was damaged in shipping, or any of a number of
    other possibilities. Before passing judgment, maybe we should wait to see
    how the seller treats the OP.
     
  19. Just a guess, since it seems I was having a similar problem with my scope
    (Tek 2235 - 100Mhz). Are you grounding the probe? There should be a clip
    that comes off the probe to ground it. Sorry if my answer seems obvious,
    just thought I'd throw my 2 cents in. Good luck.

    Scott
     
  20. I haven't passed judgement. I'm just pointing out a fact about ebay. The
    real issue is that ebay doesn't really care about it. If it any fault then
    it would be ebays.
     
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