TV PSU Mod help needed

Discussion in 'The Projects Forum' started by Blacksypher, Apr 29, 2011.

  1. Blacksypher

    Thread Starter Member

    Apr 29, 2011
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    I'm currently trying to convert a 846-240-H3CZZSH to function as the 860-AZ0-MLT666AMH which are 2 different types of psu for the same tv .

    Now my problem is that the 846-240-H3CZZSH doesn't have the 12V line required to activate the 5VSB from the control board .. now the 846-240-H3CZZSH has three 24V lines I only need one the other two are not used.I'm wondering is it possible to split one of the 24V lines into two 12V lines and use one to send to the Control board and the other is not going to be used?

    Normally I would just take two 1Ω resistors to split the 24V, but due to the design of the board i only have one output so that method wont work as I can't split one output into two or am I wrong? The 12V line is required to turn on the rest of the PSU so unless I can do this im screwed. EDIT: To be more specific if I can split the 24V into two 12V does the other 12V have to go somewhere?

    Also the design of the control boards are different. I believe its just how they use the three 24V to cycle the power to the same requirements of my board (this is just different revision of the boards)

    Note: on attachments
    1.jpg = the difference between the 2 control boards
    2.jpg = my control board
    3(WIP).jpg = what i have done so far
    HPIMG0545.jpg = full img of old PSU which i no longer have.

    Thank you for any help you can provide.
     
  2. Blacksypher

    Thread Starter Member

    Apr 29, 2011
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    Could I Run 2 Resistors in series, and half the voltage? obviously i would rather not use a method that leaves me with a unused 12V line.
    for example. this is a 12V circuit but the principal is the same.
    [​IMG]

    granted in my case the - end of the connection is the control board connection.
    so would i still use a 1Ω resistor? or a 1000Ω?


    I would also like to add my skill in electronics design is still limited but i'm working on expanding my abilities.

    if i still had to the old psu I would just replace the burnt out parts. but sadly i don't. and the one im using now was given to me by someone with the same tv but it was later revision of the control box. and I can't afford to just replace the board as it costs $350.00 and thats something I can't afford at this time.
     
    Last edited: Apr 30, 2011
  3. retched

    AAC Fanatic!

    Dec 5, 2009
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    If you are trying to make a resistive divider, the voltage split is dependent on the RATIO of the values, not the values themselves.

    Now, the values DO have a role to play in the available current available at a particular temperature.

    http://www.allaboutcircuits.com/vol_1/chpt_6/1.html
     
    Blacksypher likes this.
  4. Blacksypher

    Thread Starter Member

    Apr 29, 2011
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    thats the info i was looking for .. i'll let you know how it goes .. and if i have issue or questions.
     
  5. Blacksypher

    Thread Starter Member

    Apr 29, 2011
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    ok how do i hook the meter in series to check current without have a way to complete the ciruit as im testing the 24V output (1 connector).

    to be more specific what can I use to close the circuit , as im already at the terminal output. I only ask as for me to calulate what resistor i need . i need the amps the PSU pulls.
     
    Last edited: May 1, 2011
  6. retched

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  7. Blacksypher

    Thread Starter Member

    Apr 29, 2011
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    well if you look at the board its has the terminals of 3 grounds 3 24V outputs a 5VSB how do i test current for that output (24V) when its the end of the circuit
     
  8. Blacksypher

    Thread Starter Member

    Apr 29, 2011
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    I dont want to pass current to the control board till i have the 12V line. as i dont want to risk damaging the control board.
    normally i would just connect the multimeter in between the output and the control board.
     
  9. Blacksypher

    Thread Starter Member

    Apr 29, 2011
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    so yes im having issues closing the circuit to test the current
     
  10. retched

    AAC Fanatic!

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    You will have to OPEN the circuit where you want to test.

    For instance, if you want to know the amount of current running through a motor, you dont need to check at the wall, you can check by pulling one of the motor leads and attaching the meter as shown in post 6.

    You can pull a lead off the battery and connect the meter to show the entire circuit draw. (Be sure to set your meter correctly, and move the probe to the proper input on the meter.)

    If you have three 24v inputs, you can pull them 1 at a time and add together the results you get.
     
  11. Blacksypher

    Thread Starter Member

    Apr 29, 2011
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    retched I would also like to thank you for the help you provided so far. really wish other forums would be as helpful ( new forum member status useually gets me ignored.)
     
  12. retched

    AAC Fanatic!

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    No problem friend.

    Here to help..and be helped. ;)

    In two months someone may have the same problem as you, so this thread will serve for a long time to come.

    All I ask is you post your results so that future readers can see what the result actually is, good or bad.
     
  13. Blacksypher

    Thread Starter Member

    Apr 29, 2011
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    3(WIP).jpg the (1) is the connector in question . and its a output. the input is the control board. so would I have to find the spot on the board just before the output or what? as I can't use the control board to complete the circuit anyways as the 12V is required to send to the 5VSB to the power supply to turn on the rest of the power.The lcd screen connector is only reading 23V because the 12V powers the rest of the control board and sends the rest back threw the 5vsb to turn on the rest of power supply and gives the rest of the connectors the 1V they need to turn on the screen. guess the best thing i can say is its the fact this is a power supply. and im confused where to actually connect the multimeter in series to test output current for the board in question
     
    Last edited: May 1, 2011
  14. Blacksypher

    Thread Starter Member

    Apr 29, 2011
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    and wouldn't the full control board need to be on to get an accurate current and its the full circuit?
     
  15. Blacksypher

    Thread Starter Member

    Apr 29, 2011
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    im kinda new to testing current ... I usually only test Voltage, resistance, impudence, and continuity.
     
  16. Blacksypher

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    Apr 29, 2011
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    could I use one of the + or - leads at the beginning of the power supply where the plug comes to the board and then the output 24V connector?
     
  17. retched

    AAC Fanatic!

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    Noooo.

    One lead would be BEFORE the regulators dropped the voltage to 24v.

    Come to think of it, if you can find the regulators, you may only have to change a set resistor to change the voltage from 24v to 12v.

    Can you follow the traces back to see what type of voltage regulators this uses?
     
  18. Blacksypher

    Thread Starter Member

    Apr 29, 2011
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    your right there are 3 regulators and 3 24v markings on them
     
  19. retched

    AAC Fanatic!

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    Can you read any other marking on the regulators?

    Maybe take a CLEAR picture?
     
  20. retched

    AAC Fanatic!

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    Actually, do you have access to the schematic to the new supply? (Hopefully in PDF format)
     
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