Multimeter Checking Manual

Discussion in 'General Electronics Chat' started by cappanie, Jan 23, 2006.

  1. cappanie

    Thread Starter New Member

    Jan 23, 2006
    4
    0
    Hello,
    New to this site, just to find out, any of members here familiar with multimeters?,
    basically i just ant to know how to use this meters, (i'm using analog meter), currently, didn't know to adjust the range for some electronic components and scale readings.
    can anyone help?

    tq

    cappanie
     
  2. mozikluv

    AAC Fanatic!

    Jan 22, 2004
    1,437
    1

    hi

    try to browse thru this:

    Analogue multimeter

    here's some basic stuff:
    1. when using the ohmmeter at any range, in order to have a fairly accurate reading always zero the meter scale first. you do this by shorting the probes and start tweaking the pot until you obtain the zero reading
    2. the ohms range figures are your multiplier. for example the 1k range, any reading in the scale is multiplied by 1000. if it's 10k, it's multiplied by 10,000
    3. try to use the range w/c is near and higher than the value you are about to check to obtain a fairly accurate reading.

    4. for dc voltage test, always set the range that can accomodate the voltage to be tested. if you are not sure of the voltage always use highest range. once you know, you can now set it to the appropiate range to obtain an accurate reading

    5. step 4 is also applicable to ac voltage test.

    6. in using the ammeter, also go 1st to the highest range and gradually go down to the appropiate level.

    hope this gives you a start.

    moz
     
  3. cappanie

    Thread Starter New Member

    Jan 23, 2006
    4
    0
    Basically, i just wanted to know how read transistor readings, since this analog meters confusing me always.please help me

    cappanie
     
  4. mozikluv

    AAC Fanatic!

    Jan 22, 2004
    1,437
    1
    hi

    let's try to be specific. what kind of test are you trying to do with a transistor.

    1. are you trying to identify the pin assignment of the device?

    2. are you just trying to test whether the device is good or bad?

    3. are you trying to test the device alone or is it on a circuit board.

    4. are you trying to check the hfe of the device?

    5. are you trying to identify whether the device is an NPN or PNP?

    w/c of the above are you trying to do.

    moz
     
  5. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    I find analogues actually best for doing a quick and dirty transistor test.
    For an NPN (out of circuit) using ohms x 1 put the negative (black) probe to the base, and the red lead to the collector, then to the emitter. The meter should read a similar value for both, probably somewhere between 20 to 50 ohms..(not a short, not open circuit).
    Reverse the test with the red lead on the base, and black to collector then to emitter. It should be open circuit... check by going up to ohms x 100.... it should still show open circuit.
    Then measure across emitter to collector swapping probes for the second test to check for leakage in either direction. Again, their should be no meter deflection.

    To measure a PNP use the same test, but reverse lead polaritys.
    If measured in circuit, other circuitry may give you bad leakage figures.
    Darlingtons will look leaky as well.

    Hope that helps a little.
     
  6. cappanie

    Thread Starter New Member

    Jan 23, 2006
    4
    0
    mozikluv,
    thanks for your very clear questions!

    The story like this, month ago , my television got electric shock, managed to open the back case, the fuse blown!,replaced but still no power at all, tried to discuss with friends,one of them told me probably,the power transistor gone, now the problems is i don't know how to test the transistor wheather good or bad?, for your information i has taken the transistor from board. (transistor form left,label faced to us, first leg is base ,2nd is collector,3rd is emitter. please guide me how to solve this problem.please inform also the setting of anolog meter for checking this components.please guide me for question no 5 as well. and i like to thanks also gadget for sharing !
     
  7. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    There are a lot of power transistors in a TV. Most likely there is a fault in the Switch Mode Power supply section of the TV. First, check the Rectifier Diodes at the mains input, and also check that the Deguass circuit isn't shorted by unplugging the Deguass coils.
    Next check the power SMP component, which may be a power transistor, or more likely a Power IC. Then check any controller components. If all OK, then may be a crook Line output stage, or Frame stage. Probably a job for the Professional, as any service of a TV involves working with some fairly nasty voltages.
     
  8. cappanie

    Thread Starter New Member

    Jan 23, 2006
    4
    0
    Well, i've has checked all rectifier diode's all working condition (taken out from the board)
    i'm suspicious to transistor (big one) attached with heatsink , labeled as sk4804 and another one is with five legs, first leg is straight,2-4 slightly adjusted like chair,and the last one on right same as first leg, can i know this component used for? what purpose ?(labeled as str d5095) then how to check ? .seriously i'm very sick to learn electronics !
    please help me
     
  9. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    They'll be Power I/Cs.... STR type regulators are a common Power device in SMP power supplies. Without checking I cant tell you what sort of voltages to expect on the pins, but i suggest either getting a circuit diagram of the set, or at the very least doing a search on the net for STR D5095, as an application sheet may show you what to expect.
    Can't help much more, most repairs are best done on my Workbench, not via remote control.
     
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