The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

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  • RCA Alarm Clock: Recapping

    A power failure apparently pushed the ancient RCA alarm clock over the edge into a mode where it ignored its pushbuttons and displayed a time based on a hitherto unknown exoplanet. Popping the case revealed it’s been simmering in its own juices for quite a while:

    RCA Alarm Clock - PCB overheat
    RCA Alarm Clock – PCB overheat

    There’s nothing obviously scorched on the underside of the PCB, although a large SMD resistor might be the source of the problem.

    Having been around this block a few times, I unsoldered that big electrolytic cap with its guts protruding from the overwrap:

    RCA Alarm Clock - failed cap value
    RCA Alarm Clock – failed cap value

    Nope, that’s not really an electrolytic cap any more.

    Lacking a 2200 µF cap of suitable voltage rating, but knowing cap tolerances allow for considerable windage, this worked out well enough:

    RCA Alarm Clock - replacement caps
    RCA Alarm Clock – replacement caps

    Two smaller caps measuring on the low side of OK now reside in the e-waste box.

    The white diffuser over the last digit improves it in ways I do not profess to understand, but am pleased to implement:

    RCA Alarm Clock - in place
    RCA Alarm Clock – in place

    It’s held in place by two strips of LSE tape to see how it reacts to prolonged shear force, no matter how gentle.