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Help for test uc3845

Discussion in 'General Electronics Discussion' started by Oldsnake00, Mar 20, 2016.

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  1. Oldsnake00

    Oldsnake00

    33
    0
    Apr 15, 2015
    Hi all
    I want to test ic uc3845 form below circuit but I no have transformer. After finish circuit wiring I use osc. Measure signial from pin6. It no output.How to modify circuit for use osc. measure signalfrom pin6?
    Screenshot_2016-03-20-13-05-27.png
     
  2. Oldsnake00

    Oldsnake00

    33
    0
    Apr 15, 2015
    To day I wiring circuit without transformer and feedback.and check signal at pin6 with osc. Why the uc3845 not send pulse from pin output(pin6)?
    20160320_190059.jpg 20160320_190126.jpg
     
  3. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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  4. 73's de Edd

    73's de Edd

    2,879
    1,217
    Aug 21, 2015
    .

    Sir Oldsnake00 . . . . . .



    If I am reading between the lines and you are basically wanting to test a UC3845 of yours.
    The simplest way I know is to refer to the old Unitrode Switchmode Design
    Manual and breadboard up and try out the simplistic circuit of figure 28 on Page 3-64 of the info that I am providing you below.

    ( Hmmmmmmmm . . . . I now see that Tejas Instrumentations is now their big Sugar Daddy )

    http://www.ti.com/lit/an/slua143/slua143.pdf

    The USUAL failure mode on this family of devices is for one of the final totem pole driver transistors to fail.


    73's de Edd

    .
     
    Last edited: Mar 21, 2016
  5. Oldsnake00

    Oldsnake00

    33
    0
    Apr 15, 2015
    Thanks. All
    I change cap. from 47pf to 1nf and res. 47k to 10k the uc3845 generate pulse about 80khz.
    :D
     
  6. 73's de Edd

    73's de Edd

    2,879
    1,217
    Aug 21, 2015
    .

    Yep . . . . .that circuit was what I built up on a custom built board with an I.C. plug in socket for testing those devices
    to evaluate one to see if it was basically good.
    Seems like that family was introduced in the mid-late nineties.
    A 100 ohm load resistor was used to present a challenging load for its capacitive doubler circuit .
    Nowadays that chip still seems to be the principal building block for computer power supplys and others.

    73's de Edd
     
  7. Oldsnake00

    Oldsnake00

    33
    0
    Apr 15, 2015
    Thank you.
    This project build for caustom cdi to use on my old bike.
     
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