Bad caps in Lexus instrument cluster

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  • KeriJane
    Mac Enthusiast
    • Sep 2008
    • 681
    • USA

    #1

    Bad caps in Lexus instrument cluster

    My latest recap..... The "#1 and "#2 circuit boards" out of an elderly Lexus LS400.

    "The dash lights won't work when cold and the new circuit board is over $800"

    It has high-voltage CCFL lighting for the instruments but surpisingly, the high-voltage section seemed OK and all of the larger NCC SXE series caps seemed to have pretty good ESR.

    A little Internet research pointed me to the right place.... Most of the small caps that look like polymers had extremely high ESR! The best one was like 28 ohm, the rest returned no reading.

    It seems that the fuel gauge and instrument lights are controlled by an onboard processor of some kind that needs just a little filtering to operate. 10, 1 and 4.7mfd doesn't seem like much but the lack of these tiny, SMD mounted caps kills the lights and the fuel gauge.

    I didn't have time for pics of the board but I can add pics of the old ones.
    In went some Nichicon PW of the same ratings and the cluster sprang back to life.

    The original caps had their leads pulled through a plastic mount and bent over to form a SMD package. Getting the new caps in place was a little touchy as the originals were put on a hot board and I was using just an iron.

    It's easy to cry "foul" and "bad, cheap caps" but this car was made in 1993 and is old enough to vote. 18 years seems pretty good actually.

    It just reminds me that today's cars are way too complicated for my tastes.

    Il stick to my Trabbi.
    The More You Learn The Less You Know!
  • Krankshaft
    Badcaps Legend
    • Jan 2007
    • 2328
    • USA

    #2
    Re: Bad caps in Lexus instrument cluster

    It seems the guys at Toyota were looking to differentiate themselves from the standard incandescent dash lights with the CCFLs.

    The main reason why they went with them instead of LEDs is they can be easily dimmmed by adjusting the voltage on an input wire to the inverter. Pretty ahead of it's time using CCFLs in 93.

    LEDs can't be dimmed in such a simple way if you drop below their forward voltage they instantly go out. You need a PWM supply to control the duty cycle to adjust their brightness.

    What are they using nowadays to light the dashes LEDs and electroluminescent sheets? I've lost track.
    Last edited by Krankshaft; 09-29-2011, 01:57 AM.
    Elements of the past and the future combining to make something not quite as good as either.

    Comment

    • kc8adu
      Super Moderator
      • Nov 2003
      • 8832
      • U.S.A!

      #3
      Re: Bad caps in Lexus instrument cluster

      yeah the imfamous smd lytic.no good for anything but to ensure the item will drop dead in a few years.
      good save!

      Comment

      • ipman
        Senior Member
        • Jul 2011
        • 159

        #4
        Re: Bad caps in Lexus instrument cluster

        Nowadays they used leds (all colors) allmost anywhere in cars.

        Comment

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