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EEVblog #1334 – Mystery Dumpster Teardown

Mystery dumpster teardown time! With the most amazing mechanical mains power switch you’ll ever see! ...

9 comments

  1. Of course the power supply was worked on. Look at that TO-220 transistor at 7:45. It was salvaged from somewhere else, where it was screwed on top of dielectric pad, and that dielectric pad is still there stuck on the package.

  2. What’s up with the banana on top of the DSA? 🙂

  3. With a large mains transformer, changing the input voltage selector 2:1 should make a 4:1 change in primary resistance, not 2:1 as in the video. This is because you have two separate windings that are put in parallel for 120V or series for 240V. In this video the transformer must have single winding tapped at 50%. That means the 120V half section of the winding has to be rated at the full VA of the transformer, and so it uses more copper than necessary. Okay for small trannies maybe but not bigger ones.

  4. Bananas are standard for DSAs. For a DSO, of course, it’s apples. Or possibly something more exotic in Australia, but in the US it’s apples.

  5. When you first powered it up, the LED displays were very bright and faded over time.. Was that just exposure on the camera or did they really fade?

  6. On your DSA, wouldn’t the “chirp” mode be your frequency sweep? I mean a chirp is defined by three parameters – start frequency, end frequency and duration and that signal is monotonically increasing (or decreasing) through the duration.

    I.e., frequency sweep.

    (It’s a special type of impulse response – you give it a pulse and it gives you a stretched pulse. The end result is if you feed that lengthened sweep back into an inverse chirp (sweep the other way) you get the original pulse back. So it’s used for radars and such).

    Also these days – would such a device still use passive and active filters, or will they just stick the input signal into a reasonably fast ADC (it’s 100kHz – 192kHz sampling/24bit audio DACs are cheap, plentiful, precise and accurate which get you 96% of the way there) and then shove it into a DSP and then a DAC?

  7. There is a DC coupling for a High pass filter ? Why ?

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