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  1. #1
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    13.9 V instead of 2.75 v, Which parts are failing?

    Hello,

    I am having trouble finding which parts are bad and causing I am getting 13.9 Volts instead of 2.75 Volts with pin 8 of X530 connector (red question mark)?
    X530 pin 8 is only for test and is not connected anywhere. Please advice which parts are failed and needs replacement in your opinion?

    thx

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  2. #2
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    Re: 13.9 V instead of 2.75 v, Which parts are failing?

    your schematic is very hard to read

    what is N403?
    what does the red line below and to right of red "?" connect to?

    without information about parts and what you are expecting it to do,
    it is difficult to suggest broken parts

    are the voltages and currents that lead to this 2.75 V location correct?



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  3. #3
    Full Member level 3
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    Re: 13.9 V instead of 2.75 v, Which parts are failing?

    Both N403 and N2 are OP07 operational amplifiers. I don't have better quality schematic. Red line shows connection of the X522 pin 8 to X570 pin 8 of another board. Pin 8 of X522 carrying a regulator signal. Regarding voltages and currents I don't know. All I can measure is X530 pin 8 voltage. This pin is for test.



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  4. #4
    Full Member level 3
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    Re: 13.9 V instead of 2.75 v, Which parts are failing?

    I checked V403 and V402 diodes on board and they are OK (0.7 forward and 1 revers selecting ohmmeter diode test). Also I checked R419, R405 and R420 resistors on board and all have correct resistances. Also voltage at the input (left side of R416 and R417) are both zero with respect to the ground. These voltages are OK according to the document. So this 13.9 v could only be coming from P15V (power supply voltage). Right? I guess only suspicion part is the OP07 operational amplifier now. Right?

    Please advice if you have any other suggestions.

    thx



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