LOW VOLTAGE Circuit TESTER lamps

Discussion in 'General Electronics Chat' started by relicmarks, Nov 2, 2008.

  1. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    I'm trying to test for shorts,opens,breaks/broken wires or traces

    Its hard using a DVM meter set on Continuity Tester "when the power is *ON* a circuit" or a Analog meter set on RX1 because i still get resistance OHMS from the probe wires and the "in circuit" test resistance

    A Low voltage circuit tester with Lamp , Quick checks both AC & DC current up to 28 volts w/ power on. Helps locate shorts or breaks

    The Lamps bulb should only light/glow if the circuit is complete if not there is a short or open/break

    Shorts- The lamps bulb will light/glow
    Opens- the Lamps bulb will be off/dead
    Breaks- the lamps bulb will be off/dead
    broken wire or traces- the lamps bulb will be off/dead
    bad connection- the lamps bulb will be off/dead
    Shunt or bridge- The lamps bulb will light/glow

    Examples of using a Low voltage circuit tester with Lamp

    Testing for DC 12 volt shorts:

    1.) Check 12 volt short across the main connector from + positive to - Negative on the mother board of the circuit

    2.) check 12 volt short across the VCC and ground of the IC chips

    3.) Check 12 volt short across decoupling capacitors or filter capacitors

    4.) Any other 12 volt short checks?

    ::Testing for TTL signals :

    1.) Check for the Clock pulse, the low voltage circuit testers lamp should be blicking or pulse at a fast rate. If the lamp is dead than the clock signal is bad

    2.) Check for TTL signals, place the low voltage circuit tester on the input of the source of the TTL signal , it should be blinking or pulsing at a rate. Than go to each output and input from stage to stage until you find their the LAMP is dead/not blinking or pulsing

    ::Checking for 6,12,28 volt AC sinewave signals:

    1.) When testing AC signals with a low voltage circuit tester lamp , we have to add a blocking capacitor to block DC signals and only allow AC signals

    2.) Place the low voltage circuit tester on the input of the source of the AC signal, the lamps light should be dimming up and down since its a sinewaveform. Next go from output to input of each stage until you see the LAMP dead


    The low voltage circuit tester lamp is great for testing Shorts when the power is ON

    Mostly if you have 6,12,28 volt shorts when the power is ON , most likely you will smell chips burning or getting hot

    But if you use a Variac it might help because the power will be still ON and then you can locate where the DC SHORT is with a low voltage circuit tester lamp with the power still ON
     
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Is this a commercially made tester, or did you make it, or is it still in the "concept" stage?
     
  3. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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  4. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Those things are for cars. They draw way too much current to be generally useful for testing electronic components, such as TTL.
     
  5. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    What kind of lamp bulb would i need than?

    12volt bulb at what current for solid state circuits?

    6 volt bulb at what current for TTL?

    Cause you can open it up and change the Bulb inside it, and than i can put it a solid state bulb and TTL bulb to do testing with
     
  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    I have never found much use for a bulb or lamp as a general troubleshooting tool. A multimeter is the single most useful piece of test equipment you can own. Read this article to learn more about multimeters. You can get either analog or digital, and each has advantages and disadvantages. If you're on a limited budget, go to www.harborfreight.com and search for "multimeter". Also search Ebay for multimeter, dmm, vom, etc.

    EDIT: i see from your other post that you have a DVM. You should be able to do most of what you need with that. I have seen circuit testers that have LEDs to test digital waveforms, but they are IMHO of limited usefulness.
     
    Last edited: Nov 2, 2008
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