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Scope calibration

Discussion in 'Troubleshooting and Repair' started by Saul Britto, Mar 4, 2016.

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  1. Saul Britto

    Saul Britto

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    Mar 4, 2016
    Hi all. It's possible to calibrate an oscilloscope with a good SG and a frequency counter?
    I need to put in good condiction a HP1741A that was solved last week,but I never did a calibration.
    It has a small problem of time base showing more cycles than normal.
     
  2. dorke

    dorke

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    Jun 20, 2015
    It is possible.
    But first, is the vertical vernier in the CAL. position?
     
  3. Saul Britto

    Saul Britto

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    Mar 4, 2016
    Yes it's in CAL position
     
  4. dorke

    dorke

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    Jun 20, 2015
    You do have a CAL point on the scope.
    Are you working in "main mode" or mixed or DLYD ?
    Is the scope not calibrated in all time base positions?
    By how much in % is it not calibrated?
     
    Last edited: Mar 5, 2016
  5. Saul Britto

    Saul Britto

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    Mar 4, 2016
    Ok I am at main mode I think it's problem is in the 0.005 uSEC
    Measuring a 24mhz signal Isee 12,5 cycles when was to be 12 cycles.
    I need to fix a problem of trigger offset but don't know the nomenclature that HP uses for.
    Know you where is the H lenght on 1741A?
     
    Last edited: Mar 5, 2016
  6. dorke

    dorke

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    Jun 20, 2015
  7. Saul Britto

    Saul Britto

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    Mar 4, 2016
    I already has a service manual for 1741A,I will do some photos for you to evaluate.
    This scope had many problems that I repaired. It just need a calibration.
    It came to me with the cathode in cut,was a photocoupler on the HVPS,there was problems on the vertical,gate. It looks like an excelente machine.
    Oops Dorky! Please, this scope isn't 1741A, is 1740A sorry guy. The 1741A is another history.
     
    Last edited: Mar 5, 2016
  8. Saul Britto

    Saul Britto

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    Mar 4, 2016
    Friends please: where do you read HP1741A understand HP1740A.
     
  9. dorke

    dorke

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    Jun 20, 2015
    O.K
    Do you have the service manual of the HP1740A?
     
  10. Saul Britto

    Saul Britto

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    Mar 4, 2016
  11. shrtrnd

    shrtrnd

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    Jan 15, 2010
    I'll just add this input. I work in an electronics standards lab.
    I've read a lot of posts over the years here from people asking about calibration. And I've interpreted them to mean different things for different people.
    'Calibrated', just seems to mean 'in the ballpark' for most people, and I suppose in a lot of applications, that's all that's really needed.
    I don't know your application, but you're talking 0.005 usec. You need a standard for that. A precision instrument, in the U.S. traceable to NIST (used to be the National Bureau of Standards).
    If you're working 'in the ballpark', good luck. If this is a critical work scope, you should have it calibrated by a licensed electronic standards lab.
    So much for my input.
     
  12. Saul Britto

    Saul Britto

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    Mar 4, 2016
    Not so 0.005uSEC there are some others things that are clear to me that, needs adjustments mainly because, I want to learn how to calibrate the minimum in an oscilloscope. As I said before: I can fix such machine very easily but, still not a calibration.I bought this scope in a situation of just for parts and, basicly rebuild it. Let me do a correction: the time is .05 uSEC.
    Saul.
     
    Last edited: Mar 8, 2016
  13. shrtrnd

    shrtrnd

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    Jan 15, 2010
    I know what you're saying. My input is just that calibration to factory specs is one thing, and getting the scope to what others might consider acceptable, is another.
    Good work on the scope repair.
     
  14. dorke

    dorke

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    Jun 20, 2015
    This calibrator is a professional tool.
    I wouldn't buy it unless you are in the business of fixing test equipment like scopes,frequency counters etc.

    In this case, I think it is more expansive than the scope you are trying to fix...
    and it is absolutely not needed,there are many other ways to generate accurate frequencies for a lot less money .
     
  15. shrtrnd

    shrtrnd

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    Jan 15, 2010
    I rest my case.
     
  16. Saul Britto

    Saul Britto

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    Mar 4, 2016
    As you read above I can fix a scope easyly,just do not calibration and I am on the business. I am intending to enter deeper into the business
     
  17. Saul Britto

    Saul Britto

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    Mar 4, 2016
    Thank you.
     
  18. dorke

    dorke

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    Jun 20, 2015
    In this case .you should buy professional equipment.

    It calls for a deeper study of the calibration equipment needed for now days test instruments, and do it wisely since they are mucho-dinero;)
    That HP1740 is almost a museum item.
     
  19. Saul Britto

    Saul Britto

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    Mar 4, 2016
    As I said before I need to learn. I think you will not to buy a teledyne lecroy just to learn...
    A 1740A is sufficient. Do not be fooled, an old HP does things that some modern digital can not, complex signals are an example.
     
  20. Saul Britto

    Saul Britto

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    Mar 4, 2016
    A days ago I made an equipment that uses the XY mode and a digital scope made me ashamed.

    Another exemple? I did need to measure 5KV and as do you know was with a HV probe I did try to use a DMM but it gave me a wrong result but, a VTVM solved the problem.
     
    Last edited: Mar 10, 2016
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