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Can someone help me sort these 2 hot resistors ?

Discussion in 'Troubleshooting and Repair' started by Sillencio, Nov 6, 2019.

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  1. Sillencio

    Sillencio

    2
    0
    Nov 6, 2019
    Hello. This is my first thread here. I am having issues with this LTC PAA210CD amplifier. The biggest problem are these two resistors which get extremely hot when the amp is on. Can someone help me to sort this problem out ? I would really appreciate it.
     

    Attached Files:

  2. duke37

    duke37

    5,301
    740
    Jan 9, 2011
    You need a circuit diagram, Does it work?
    The resistors are close to the output transistors so they may be linked. Check the output transistors for shorts.
    There are enough transistors for a stereo set so you could compare the voltages on one channel with the other. Use a lamp limiter to reduce the voltage and limit the current.
     
  3. Bluejets

    Bluejets

    3,784
    783
    Oct 5, 2014
    Look like output transistor ballast resistors and with a 5w rating I would imagine it would be normal to get "hot" if that is a form of test procedure.:)
     
  4. 73's de Edd

    73's de Edd

    2,805
    1,176
    Aug 21, 2015
    Sir Sillencio / quiet . . . . . . . .


    Referencing to your photo #1 . . .

    You have two sets of two power transistors arranged across the top, being mounted to the heatsink.
    There is an associated 0.22 ohm @ 5 W ceramic cased resistor below each power transistor.
    Of those . . . . the 2nd resistor has seen extended heat strain.
    That is thereby suggesting a severe or increased current drain being related to the second transistor.
    Now . . . .are both of your audio channels working and if so is the power and quality of sound being the same ?
    OR . . . is one channel being dead ? . . .or distorted ?

    A start of analysis could be to take a DVM in DC mode and set at a very low range ( unless autoranging) , then power up the unit with no music input and measure across the 3rd resistors leads and log down. Then measure across the 4th resistors leads . . .log down.
    Now aren't they being about the same ? . . . . . highly suspicioned . . . . . .
    Then move to the 1st resistor and measure across it . . .log it down. Finally, measure across the 2nd resistor and that one should show a somewhat higher reading, than the others.
    Also, can you confirm that all 4 transistors are being 2sC5198's.

    Standing by . . . . . . .

    73's de Edd . . . . .

    Shin:
    An anatomical part of the body, principally used for finding furniture in the dark.



    .
     
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  5. Sillencio

    Sillencio

    2
    0
    Nov 6, 2019
    Hello Edd. I just want to say that you saved my day ! All i did is replaced the pair of resistors and the pair of transistors, and the amp works without a bit of heat. Thanks once more !!
     
  6. 73's de Edd

    73's de Edd

    2,805
    1,176
    Aug 21, 2015
    REJOICE ! . . . . . now . . . . . Let there be music . . . .
     
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