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”).
Damn, that’s so sick. Using this unit actually made me want to buy one for myself and take the CRT module out of it. Do you know if the module exposes the high voltage parts like TVs do, or is it safer to work with?
Edit: also have you been to Maker Fair Prague? I missed the one this year but I’m considering going to the one in Germany
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).
Ok, that truly is unbelievably cool. I see on your Mastodon that you also played with those S-Bahn segmented displays that I’ve always been curious about
Not me, I just theorized. I met people from C3PB (@[email protected]) with their giant Parklight24 display and wondered what it could be used for. Also, @[email protected] had a Geascript display at 39c3, smaller (U/S-Bahn single liner in train) but with proportional font.
Oh is it hitting the screen from the front instead of the back?
Yeah, the screen is slanted and it’s hitting it from underneath
Yup. The metal anode is phosphor-coated. What’s more interesting: it’s using a standard “defection IC” to detect sync pulses and generate horizontal and vertical ramps but the focus and horizontal width change dynamically as the picture is scanned top-to-bottom to achieve keystone correction and maintain sharpness.
For the curious: you can actually see the CRT electron gun if you look closely enough
If the microwave is broken you can put a Hotpocket up to it for 2 minutes.
The power draw is 4 watts, not much more than a color LCD of this size and brightness, and most of it is the CRT heater. Very little ionizing radiation at 3 kV.
Bigger CRT TVs are even more power efficient by screen area, especially transistorized B/W ones, which were about as good as CCFL-backlit color LCDs.
4W is impressive given how high voltages are needed for any CRT. I suppose the current must be minuscule to compensate?
The anode current for such a small screen area is pretty low. The flyback also provides a few hundred V to 1 kV for various grids like focus and brightness of the electron gun. 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.
