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    EEVblog #1022 – Finding A $50 Oscilloscope On Ebay

    Another look at finding a $50 analog oscilloscope on ebay. Forum HERE Podcast: DownloadBe Sociable, ...

    • Chris Davis

      I’m sure I’ve already seen this??

    • hdavis

      Not to freak you out, but I wonder if the covering on the back is asbestos. I’m sure they would want to fireproof the electronics especially after the Apollo 1 fire.

      • Could be. But only really dangerous if you grind the stuff up.

    • Synthetase

      I don’t think those chips are as under-utilised as you’ve mentioned, I think they’re double sided (at least), which means that although it looks like half the pins aren’t used on the top, they’re going to circuitry on the bottom. Observations: at 14:29 we get the circuit diagram and silicon etch tracks of the inverter. Pin nine is shown in the schematic to be connected to the pull-up resistor on the common anode of the diodes (and thence to pin 1), but it’s not connected on the ‘top view’ etch diagram, which leads me to assume all that apparent spare space on the top, has traces along the bottom going to pins 9, 10, 11. From here, I reason that the main limiting factor on these things (at least in the way they are being used) is the number of pins, not the minimum size of the die. As you say, it’s not like you couldn’t fit another few comonents in the space on the tops of the chips that have already been uncovered, just that all the pins have been used, so there’s no way of connecting the extra components to the outside world.

      Anyway, fascinating look back into the history of the integrated circuit, Dave. Cheers 🙂

    • tlhIngan

      Fundamentals Friday suggestioh – how DTL logic works and explain how that inverter works.

      • Bruno Kremel

        That is actually pretty simple.. just look at diagram of that DTL inverter and imagine 0V and then 5V on input.. I think that you’ll figure out rest.

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