esr meter with tone project not working

Discussion in 'The Projects Forum' started by pete g, May 27, 2016.

  1. pete g

    Thread Starter New Member

    Jul 27, 2011
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    hi all, working on a project that is titled ESR METER WITH TONE. unfortunately, I can't get it to work. the link below is the project i'am working on. I had trouble trying to source a KIA75558P so I used a lm1458 instead. the circuit works up to the cathode of D3. no dc voltage is present? I have replaced D3 and C6. IF I SUPPLY AN EXTERNAL VOLTAGE TO THE CATHODE(D3), the meter responds by deflecting as it should, otherwise no meter deflection takes place(with output leads shorted). can't figure why no dc is being produced.

    http://www.qsl.net/kh6grt/page4/esrmeter/esrmeter.htm
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    Why do you think the LM1458 is a suitable replacement for the KIA75558P? Do they have the same pinouts?
     
  3. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    You can compare the pinout in the attached PDFs.

    Bertus
     
  4. wayneh

    Expert

    Sep 9, 2010
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    I'm not sure what you mean by that. Is the oscillator signal appearing at C5?
    You may like this thread, particularly towards the end where I had success using my DIY meter.
     
  5. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Is there an AC voltage on the anode of D3?
    Are the +/- supply voltages correct?
     
  6. pete g

    Thread Starter New Member

    Jul 27, 2011
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    yes, there is a 2-3vpp signal at the anode of d3. the power supply voltages are correct. I think the lm1458 should work in this circuit. the signal at the anode of d3 is moving up and down slighty, don't know if this is normal.
     
  7. wayneh

    Expert

    Sep 9, 2010
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    Do you mean the cathode, or do you mean anode with C6 disconnected?
     
  8. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Is that measured with a voltmeter or an oscilloscope? If with a 'scope, what are the voltages at the positive and negative peak of that waveform. If not with a 'scope, can you get access to one?
    [edit] And is that waveform a 100kHZ squarewave?
     
  9. dannyf

    Well-Known Member

    Sep 13, 2015
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    Doesn't seem to be anything special about kia75558. So lm1458 should work.

    I would first check power, making sure that you are getting good Rail voltages.

    Then make sure u1a is producing the right oscillatiib, the trace that waveform through the transistors base, collector, and bridges output, ....

    For what it does, the meter is overly complicated, and doesn't perform as well.
     
  10. pete g

    Thread Starter New Member

    Jul 27, 2011
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    hi guys, thanks so much for responding. the sig is present at the anode of d3 with d3 connected. i'am using an o scope the sig at the anode of d3 is approx. 2vpp at 100kc.the rail voltages are plus and minus 4.6v. the output sig at j&k is 150mv @ 100kc.
     
  11. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    What are voltages of the top and bottom of the signal at D3 anode?
    Like this image shows a square wave going from -1V to +1V.
    upload_2016-5-28_14-32-12.png
     
  12. pete g

    Thread Starter New Member

    Jul 27, 2011
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    if theres no voltage at the k of d3 that means theres no feedback volt at pin2 of u2a. what is the result of that?

    hi albert, the scope i'am using automatically shows the pp voltage. which is a sine wave at plus and minus 1volt.

    sorry, plus and minus 2vpp.
     
    Last edited by a moderator: May 28, 2016
  13. dannyf

    Well-Known Member

    Sep 13, 2015
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    That statement provides far less information than "the peak is at X volt and the trought is at Y volt, vs. ground.". A perfectly working circuit should swing 2-3Vpp without getting the diode to start to conduct.

    No idea what "j&k" is so cannot help you there.

    In general, it is helpful to others trying to help you if you post a schematic and be precise in your description of issues / measurements.
     
  14. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Please ask your scope very nicely to show you the actual voltages relative to ground not relative to each other.

    The circuit around U2A is a peak rectifier. The voltage across C6 should be equal to the positive peak of the voltage at U2A pin 3. Because the signal is capacitor coupled to pin 3 it should swing positive and negative of ground and it is the positive peak of that waveform which should be stored on C6.

    There is a reasonable description of how this works here:
    https://en.wikipedia.org/wiki/Precision_rectifier
     
  15. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    There is a link to the project, which includes a schematic in the original post.
     
  16. pete g

    Thread Starter New Member

    Jul 27, 2011
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    dannyf I posted a link to the schematic in my opening post.

    albert I asked my scope very nicely, my scope said kiss my ass!!!

    seriously, how do I make the meas you requested, al?
     
    Last edited by a moderator: May 28, 2016
  17. Papabravo

    Expert

    Feb 24, 2006
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    I would trade such a rude scope in on a better one!
     
  18. pete g

    Thread Starter New Member

    Jul 27, 2011
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    your right papa, but I don't sweat the small stuff.
     
    Last edited by a moderator: May 28, 2016
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