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relocating a hot IC

Discussion in 'Troubleshooting and Repair' started by looxuser, Mar 25, 2016.

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  1. looxuser

    looxuser

    77
    2
    Dec 28, 2015
    Hi All, I've noticed my CD player on old Hifi was troublesome, sometimes not ejecting the disc tray or spinning the disc once tray closed. On inspection I noticed heat damage around the pin landings of a dual op amp IC used for the servo functions in question (dark burnt areas) Under magnification I could see the pin landings on the PCB had lifted and many of them had cracks in the lines off to other components, Re soldering and trying to bridge these cracks has simply made them a bigger mess a lifted the traces further. That said now I've removed the IC i've managed a reasonable trace repair.

    The Op Amp is an IC with a heat displacement fin, so my question to the forum is rather than putting the op amp IC back in its original position can I relocate it and fasten via its fin to the metal case of the CD player and use some ribbon cable to wire it back to its original landing on the PCB?

    Benefits of this I see are...
    1. better heat dispersion for the IC.
    2. Less direct heat to the IC pins when trying to solder it to poor PCB landings or nearby components.
    3. Less chance i'll mess up may trace / landings repairs.
    4. I can strip back longer lengths on the ribbon cable so I can solder these and bridge gaps in PCB traces.
    5. The IC was bunched up inside a whole series of electrolytic capacitors etc so long term heat exposure from the IC to those is probably not a great design in the first place. The IC was surrounded by a fabric jacket of what appears to be heat / fire resistant matting.

    Concern is...

    5. As the PCB traces to the IC are different thicknesses (widths) would the ribbon introduce volt drops that the IC may be sensitive to thereby effecting its function. It is after all powering tiny movements of the laser motors.

    Comments appreciated folks. Cheers
     
  2. dorke

    dorke

    2,342
    665
    Jun 20, 2015
    What CD player(brand and model)?
    What IC is it?
    A photo of the area in question could help as well.
     
    davenn likes this.
  3. looxuser

    looxuser

    77
    2
    Dec 28, 2015
    Hi aiwa dx-z95, the chip is LA6510 (drive loading motor an focus coil), the area concerned i think is to tiny for my phone to focus for a picture im affaid sorry
     
  4. shrtrnd

    shrtrnd

    3,796
    503
    Jan 15, 2010
    I hate being the bearer of potential bad news, but offer my 2-cents worth here.
    It's entirely possible that normal operational heat got to the area over time if it was poorly designed.
    But I never discount the possibility that something else in the circuit went, causing the heat damage you see.
    Considering the obvious heat-related issue here, it's possible those caps dried-out and caused the damage.
    I like your idea of trying to better disperse the heat, but I'd be real careful about making sure I replaced any suspected components damaged by all that heat, before
    I just fixed the trace on the board, and worked on dissipating future heat. If the components are weak or faulty, everything is just going to heat-up all over again.
     
  5. duke37

    duke37

    5,364
    769
    Jan 9, 2011
    If you extend the connections to an op-amp, the system might go into oscillation due to added inductance and capacitince.
     
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