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Joined 2 years ago
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Cake day: June 23rd, 2024

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  • Yes, scrolling moves the content. As if it’s being gripped by the bottom of the wheel I’m rotating with my finger from the top.

    Holding a toy tire

    Imagine a toy monster truck on a sheet of paper. Push the wheels forward, page moves backward.

    Inverse scrolling is like a high-heeled rubber shoe attached to the tip of my finger advancing the page. There’s some logic to it but that’s not what a wheel is like unless it’s an Apple mouse’s touch wheel. But they can’t be trusted to design a mouse: one had a circular cross-section, another charged from the bottom.

    The big question is: which is natural? Fortunately, mice exist in nature so there’s a way to find out. Hold one tightly like this, release the front hand… Which way will the cloth move?
    Holding a lab rat



  • Yes, SCART’s features are fucking clever but it got unwieldy thick because by the spec, each cable had to be separately shielded. Even the widescreen control signal that’s mostly DC. Why not use differential pairs to reduce thickness and cost, modulate the audio and control signals together for fewer wires, and add a 5V rail to accomodate little demodulating converters (if you want separate audio devices) and eventually power PVR/tuner dongles? Most people use TV speakers anyway, that’s the whole point of a single connector of an A/V standard. Not to mention how easily it fell out, almost every other connector holds better, and the ports are hard to feel on the back of the TV. If it’s a giant 32" one nearly flush against a wall, good luck lining it up whenever you yank a controller cord and the vibration makes it fall off! And while a small STB can hang off RCA jacks, SCART sometimes disconnects by the weight of the cable itself. Or it gets angled so the video passthrough stops working and you only find later your VCR recorded just audio.

    I think it’s because of these problems, the biggest one emerged: SCART never became a worldwide standard. Nowadays, TVs are made for a world market, so even North America finally enjoys PAL-compatible sets (while most Europe-market ones and many VCRs were 3-standard since 1990), but unfortunately SCART is basically gone, not to mention very few capture cards were made with real RGB input because RCA component is stupid (why 3 connectors when no consumer ever mixes color channels? (mixing requires external sync, which is only on pro equipment and an extra cable anyway) why not decide between YPbPr and RGB before writing the standard?)

    clever Frenchies

    Don’t say that. SCART is awesome despite its flaws but the same people also cursed half of Europe with fucking SECAM. Imagine needing a 64µs, 5MHz-bandwidth delay line just to decode color at all (unlike NTSC/PAL’s QAM, SECAM’s FM allows just a single chroma channel per line, alternatingly carrying U and V axes), and a frequency-modulation+pre-emphasis system in every console/camera/DVD player to encode it, plus no color killer option (disabling the colorburst) for sharp B/W like on the Apple II!

    In PAL, information between subsequent lines was used too but only to correct recovered carrier phase between colorbursts, which was optional (cheaper sets kept NTSC-style hue controls) and could be handled by a locked oscillator rather than a whole-ass delay line (before shift registers (digital sequential-access-memory), every color set had fucking piezo transducers and physical waves travelling through precisely cut quartz, WTF?!).



  • The anode current for such a small screen area is pretty low, I’d guess tens of μA. The flyback also provides a few hundred V to 1 kV for various grids like focus and brightness of the electron gun, which take similar current. Since they all use voltages adjustable in different ranges, a single series of resistors and potentiometers is employed as an adjustable potential divider, consuming usually less than 1 mA (1 W).

    With such small sets (or ancient vacuum tube ones), the power draw of the electronics driving the deflection coils is also considerable. I’d guess about 2 W for the CRT heater, 1 W for the HV, 1 W for the sync, amplification and deflection.


  • I’ve been to 39C3 and EH23. Here’s a photo of my badge, advertising something I shadily imported to Germany :)

    https://witter.cz/@[email protected]/116374451432382202

    There is a 12V-negotiating USB-C module (I had to mod it to support any of my powerbanks, and the only one is the size of the thing, twice as heavy and a fire risk (trash-picked AlzaPower solar crap with puffed-up 20Ah cell shoddily replaced with found 6x 18650 that should last 8-10 h), but on EH23 I was smart enough to get a long-enough cable to reach a pocket so my neck didn’t hurt) and the ESP-32 is wrapped in insulating tape except the video and DIP switches (not implemented yet, I was in a rush to get any image) to prevent shorts, powered from another powerbank (the big one can’t do dual voltage).

    The screwdriver, from a shitty Merkur-like construction toy set, is plus-shaped but not as sharp as Phillips and non-magnetic, making it easy to adjust the potentiometers (a Phillips would wear them out, and a flat one would be less convenient) without the display getting all wonky (even the magnetic field inside Hamburg S-Bahn trains from their power lines makes it wobble!)

    The 3 kV is presumably only reachable via the thickly insulated wire between the flyback transformer and anode, however some high voltage does exist on the PCB between the CRT grids (for example, there’s about 48 volts between the brightness and contrast potentiometers). I used a piece of acrylic to cover the bare PCB but it fell off (shitty transparent tape) and I got shocked through my T-shirt. A little unpleasant but the current is low, especially after the small HV capacitor discharges, it felt like a normal static electricity fluffy clothing incident. I prepared the same piece of acrylic with holes for potentiometers for the front but it was matte, fell off even sooner, made it hard to adjust, and it was unlikely someone would reach inside so I abandoned it.

    I may or may not make a true solid-state sequential color TV someday. I already acquired mono TFT displays (3.5", "RGB"x320x240 except the subpixels are physically clear so effectively 960x240) and RGB LED tape that can be lit in stripes to “race the beam”: the display can be VSYNCed (in digital video mode at great expense of CPU power unlike the framebuffered SPI mode). I don’t want an annoying 20Hz flicker like the original Col’R’Tel (really, how could they sell it even in the 50s without an epilepsy warning?!) so I also bought a transparent ITO heating sheet with adhesive, the only way I can make the LCD crystals respond above 60 Hz (LCDs are way faster when heated; modern ones can do over 120 Hz at ambient temperatures but this old shitty one was the only mono TFT LCD I could afford). It could work great with an NES emulator on an ESP32, at 3.5:1 subpixel ratio (7:6≈1.17 pixel aspect ratio) I reach close to the original NES’s pixel aspect ratio of 8:7≈1.13 at high sharpness… The driver IC datasheet does not rule out overclocking up to 180 Hz, that would be perfect for the NES but the saturation would suffer (it would in daylight too)

    Mono TFT LCDs are identical to conventional RGB ones except lacking color dyes but I’m pissed they aren’t more common and thus cost a premium (usually 2x-3x). Look at the green “WC”/red “WC”/red “WC/Porucha” indicator in EC trains: a mono LCD with R/G backlight could do this with one ninth of the power (all subpixels lit red/green, not just one of three, plus color LEDs (direct or phosphor, doesn’t matter) instead of white with color filter, the only disadvantage is mild desaturation in ambient light). This applies to B/W monochrome information panels too. Also, a blue/yellow sequential-color mono LCD or 🟨⬜🟦 subpixel layout on train departure LCDs could save ½-⅔ of the power, even more in direct sunlight (and the special-subpixel ones have the advantage that color would barely degrade in sunlight, while the disadvantage is that they don’t exist AFAIK).




  • I use the screen module from one of these as a nametag at cons, upside-down of course, with an ESP32. It accepts 12V DC and regular composite video (or variations at 75 Ω, 1-1.5 Vpp AC-coupled at cca 15kHz horizontal but 45-120 Hz vertical, or presumably even more if I tweak some component values). Jan Šlehofer used a color wheel to make a Col’R’Tel and dared to call it “solid state” in his YouTube video (the nearest Czech word is tranzistorový, which means no vacuum tubes as switching devices and he does fill this criterion but “solid state” additionally means no moving parts (that would require a super rare liquid crystal color shutter - LCCS - even Daniel Kobrle aka Danyk/DiodeGoneWild was unable to source a replacement one for his luxury early digital Tektronix oscilloscope) and arguably no CRT, although even 1960s TV sets were marketed as “solid state”).