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Replace IC 4049

Discussion in 'General Electronics Discussion' started by colum, Jan 8, 2021.

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  1. colum

    colum

    136
    4
    Jul 25, 2013
    The 4049 in this circuit overheats and quits working. This IC is supposed to increase the power to drive the transistors and has alot of wires and seems like a big complication.
    Could it be replaced by 2 transistors with enough power to drive the IRF510 402720210108_16502004.jpg
     
  2. Bluejets

    Bluejets

    4,419
    938
    Oct 5, 2014
    It's cmos and transistors may drag down the preceeding circuitry.
    Has to be some reason why it is getting hot.
    Is this something you built or a commercial product...??
    Curious where the circled A on the transformer centre tap connects.
    Is this the complete diagram....??
    Mosfets appear to be an addition to the original drawing.
     
  3. Hunter64

    Hunter64

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    13
    Nov 20, 2018
    What is connected to 'A', the centre-tap of the transformer?

    Can you give more information about the transformer.
     
  4. 73's de Edd

    73's de Edd

    2,995
    1,261
    Aug 21, 2015
    Sir colum . . . . .

    What is this SUPPOSED to be ? . . . a mix? / mis? match of different circuits ?
    The right half, I can see as a 24Vcenter tapped power transformer, reverse installed, so as to then be getting 120 or 240 volts out from a hefty 12V battery.
    If being so, then at what power level are you expecting / hoping for ?
    I see the 1 ufd secondary capacitor being quasi resonant with the secondary winding to your AC line frequency . . . .50/60 ? cys..
    The higher value of the Power Present NE-2's dropping resistor value suggests of a 240V line voltage . . .right ?

    As for the joystick ? --- speed adjust--- slow functions . . . a more relevant name assignment should be, their use of setting to the appropriate twice 50 / 60 ~ line FREQUENCY.
    I can see the use of one of the shown .33 ufd time constant capacutors being switched into circuit and then setting the series string of varable resustances, such that it is being ~ 5k for the combined RC time constants, to then be creating an ~ 100cy output which is then being divided in half by your following Flip Flop pair to a 50cy drive freq. OR if working with 60~ line freq, you shoot for 120~ .


    See if this old tyme discrete transistor FET driver circuit might bail you out on your present dilemmna.
    Don't have 2222-2907's ? . . .then use the 2N39XX or 2N44XX series of complementary transistor pairs.

    RELATED SCHEMATIC REDRAW . . . . .

    upload_2021-1-8_19-1-5.png



    73's de Edd . . . . .


    Don't EVER force anything, just get a bigger hammer.

    .
     
  5. colum

    colum

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    Jul 25, 2013
    Its something I built
     
  6. colum

    colum

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    Jul 25, 2013
    OOps
     
  7. colum

    colum

    136
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    Jul 25, 2013
    Many thanks for the circuit....Its supposed to drive a variable synchrous motor and a DC motor to point a telescope, I only intend to use the synchrous drive only so its from the 555 to the 4049 works fine but once the output gets hooked up to the Transistors the 4049 heats up. without any load....Jeff
     
  8. Frankchie

    Frankchie

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    15
    Nov 14, 2017
    Does the circuit work as expected until the 4049 heats up and quits? How long does it work properly before it quits? You might try and isolate the 12v power to the IC's from the transformer power 'A'.

    You might be getting some big voltage fluctuations when the transformer draws power perhaps causing some crazy feedback, oscillations, etc. Ideally use a seperate power supply for the IC's, at least for testing.
     
  9. 73's de Edd

    73's de Edd

    2,995
    1,261
    Aug 21, 2015
    Its supposed to drive a variable synchrous motor . . .
    How about the specs from that motor as far as there being any marked fractional horsiepower or voltage and current comsumption.
     
  10. colum

    colum

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    Jul 25, 2013
    402720210112_16202357.jpg The output of the 4049 works fine with a nice even V swing until I hook it up to the transistors and without any load at all the 4049 overheats and becomes unstable V swing. I may have the wrong Trans hook up so I'm including my circuit
    Many thanks View attachment 50494
     
  11. Bluejets

    Bluejets

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    938
    Oct 5, 2014
    I don't get what the two driver transistors 2n2907 are supposed to do....no base resistance.....no mosfet gate pull down resistance.
    Possibly one mosfet still conducting when the other turns on.
     
  12. Frankchie

    Frankchie

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    15
    Nov 14, 2017
    I get an "attachment cannot be found" error when I try and view your attachment. I am assuming you are using colum's schematic.

    Anyway, measure the DC voltage across the 100 ohm gate resistors. It should be very close to zero. Any significant voltage (say >.5v) suggests there is current flow through the gate and that suggests a bad Mosfet.

    P.S. I think Bluejet has some valid concerns.
     
  13. Audioguru

    Audioguru

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    678
    Sep 24, 2016
    The transistors are ordinary complimentary emitter-followers. Emitter-followers do not need a series base resistor. The NPN pushes the gate high and the PNP pulls the gate low (push-pull). They have low input current but enough output current to quickly drive the high capacitance of the gates of Mosfets.
     
  14. Frankchie

    Frankchie

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    Nov 14, 2017

    Yes, I understand the complementary logic.
    But the emitter current is nil after the gate is low so I don't see the transistor continuing to conduct leaving the mosfet gate floating between pulses, no?

    [edit:]True if the gate floats upward the transistor will clamp it low, but that doesn't sound like good design practice.
     
    Last edited: Jan 13, 2021
  15. colum

    colum

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    Jul 25, 2013
    Thanks all for your valuable input. I think the 4 transistor option to the 4049 may be even more complicated to someone like me so I wonder if someone would make a comment on my hand written circuit earlier. Keeping in mind that there is no load on the IRFs not even the transformer so I may have a wrong IRF connections.
    The 4049 works fine with a 5V swing until its hooked up to the IRFs...Thanks...colum
     
  16. Harald Kapp

    Harald Kapp Moderator Moderator

    10,820
    2,440
    Nov 17, 2011
    Re post #10: You show a 24 V supply to the transformer but in post #1 a 12 V supply to the 4049. Are the negatives (0V, ground) of these two supplies connected? They should be. Otherwise stray currents from the driving 12 V into the 24 V circuit may create havoc.
     
  17. Frankchie

    Frankchie

    124
    15
    Nov 14, 2017
    The 4049 should have a 12v swing, not 5v. Are you using cmos 4049 or TTL?
     
  18. bertus

    bertus Moderator

    1,327
    522
    Nov 8, 2019
    Hello,

    What is the number on the used 4049?
    An 74HC4049 or 74HCT4049 can not be used as those are designed for low voltage.
    A HEF4049 or CD4049 should be used.

    The attached PDF will tell you about the levels in the various digital chips.

    Bertus
     

    Attached Files:

  19. Audioguru

    Audioguru

    3,042
    678
    Sep 24, 2016
    Why is you sketch showing the CD4027 connected to the Mosfets without the CD4049 or the complementary transistors? It should work like that but the Mosfets will switch slowly and get very hot.

    Then you said the CD4049 has a 5V swing which is way too low!

    Then you said the transistor emitters current is nil when they are connected to the Mosfets. The gate of a Mosfet is driven with a voltage, not a current. The gate voltage swing needed for an old IRF510 is 10V. Did you buy the parts from a real electronic parts distibutor or buy fakes from ebay?
    To solve these confusions then please post your schematic complete with supply voltages.
    Your sketch shows the correct connections to the Mosfets but if you tried the transistors then maybe they were connected wrong.
     
  20. colum

    colum

    136
    4
    Jul 25, 2013
    CD4049 is being used
     
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