Podcast #128: We chat with Kent C Dodds about why he loves React and discuss what life was like in the dark days before Git. Listen now.
32

Where did the 80x25 text terminal size come from? Quick answer: It's one Punch Card Per Line Resulting in 24/25 lines (cards) per screen when using a 4:3 tube and a reasonable font as dictated by proportions fostered since Roman times. Detailed Answer: Prior to the 1981 release of the IBM PC, the VT05 (72x20 1971), VT52 (80x12 1974), and VT100 (80x25 ...


31

CRT TVs are analog devices, there is no "pixel", but the size of the spot limits the resolution of the image, as the size of silver nitrate crystals limits the resolution of photo films. Several arrangements of the colour stripes on the CRT tubes have been designed, they are a compromise between resolution, luminosity and the precise alignment of the ...


24

The EHT (extra-high-tension) circuits used to drive colour CRT displays run at 25kV (kilo-volts), and the capacitors contain enough stored charge to kill you stone dead if you touch the wrong thing, and the stored charge does not disappear as soon as you switch the device off. I would take it to a repair shop if I were you. The technicians will have the ...


22

It's a little cheaper to build all-in-one units because you only need one cabinet and one power supply, and you need fewer cables and connectors and supporting electronics. And back then, people didn't often have monitors that they could reuse on new computers, just televisions which often had only RF inputs and couldn't produce a sharp image for text. So ...


19

Canonically in NTSC standards the drawn lines are tilted slightly so that the start of the odd field starting at the left is perfectly level with the top of the even field starting in the middle horizontally. The actual angle though is so tiny, ~0.09 degrees, that it's negligible compared to the rotation error you'd get just from the earth's magnetic field ...


17

The 1701 and 1702 are virtually identical. They have the same specs, tube, inputs, casing, and manufacturer. The only real difference is the 1701 is older (1982 to early '83, 1702 is late '83) and the fact that the 1701 shipped with a 5-pin composite video cable instead of an 8-pin luma-chroma cable in the box (both monitors support both inputs). A full ...


17

A lot of early PCs and terminals were designed to use either TVs or monitors that were built around CRTs that were built to the same specifications as TVs. While (traditional standard definition) TVs don't have a well defined upper limit of horizontal resolution, in practice few of them were capable of handling a signal which varied faster than about 13 or ...


15

IIRC, the electron gun was actually installed in a position where it was rotated slightly relative to the tube, to compensate for this effect, so the scan lines did end up being horizontal.


13

The 80 columns comes via IBM terminals such as the 3270, which themselves got it from IBM punched cards. There was no particular reason to pick 80 over some other width for punched cards except that it is a nice round number and reflects the engineering limits of the day. The 25 rows is due to the power-of-two nature of RAM chips. These were extremely ...


13

Horizontal deflection circuit is intended to make linearly increasing current in the deflection coil. At the end of ray scanning from left to right, the deflection coil should be re-magnetized in a short time by applying higher reverse voltage to it. Typical schematics for the circuit looks like this: http://repairfaq.cis.upenn.edu/sam/deflfaq.htm#dsbdc . ...


12

I don’t think they ever recommended a monitor. As far as I can remember, Atari communications showed Atari computers on their own, or connected to TVs; see for example this 1200XL advert, and Atari UK’s magazine, Atari I/O (issues 2, 3, 4, and 5). At least in Europe, 8-bit Ataris produced nice video on most TVs (I didn’t grow up with NTSC so I don’t know how ...


12

Yes there are a lot of compensations in a CRT like: magnets counteracting background magnetic fields circuits counteracting curvature of CRT screen surface circuits counteracting different length of the beam (edges/center) "linearizations" of brightness (gamma correction) and probably much more I can not think of right now... But back to your question the ...


11

Based on a quick perusal of the November 1982 edition of Acorn User — a user base reliably rich enough at least to consider a monitor — options then included (size unstated where the advert omits it, but I think that implies 14"): colour BMC 1401: £240, £258.75 colour Microvitec 1431: £269, £270, £284 colour MC 370M: £289 unspecified brand colour: £325, £...


11

Non-CRT monochrome screens used various colours related to the underlying technology: monochrome plasma screens were reddish-orange; see for example the PLATO terminals or the Toshiba 4400SX; early LCD screens were bluish, some more than others; I particularly remember early Toshiba laptops being notably blue (see this photo of a T1000), and many “graphical”...


10

The very short answer is no, because no “green screen” standard is compatible with VGA (which is where 640×480 was introduced). The slightly longer answer is yes, but only in a very small number of situations. The important aspect here is the signal sent from whatever system is driving the display, to the display. Early display adapters (apart from those ...


10

A typical black and white television will be capable of displaying 80-column text that can be read, but such text will generally be sufficiently unpleasant to read that some other kind of display would be preferable. Among other things, a monitor which is adjusted to have extremely sharp focus and modulate the beam very sharply will generally produce a ...


10

I've witnessed a monochrome monitor (actually, two of them) fried through software. I worked with a friend who had a weak grasp of ethics. He worked on an IBM PC/AT clone running DOS. It had both a regular CGA card driving a color CRT, and a Hercules card driving a monochrome CRT. I no longer recall why he had an extra monitor; I can only guess that it ...


10

The two specific problems you've mentioned, frame skipping and tearing aren't a function of the video card. They're software and/or CPU problems so your choice of video card don't matter. All video cards capable of outputting a PAL composite signal will output a "perfect" 50 HZ PAL signal, probably even more "perfect" in terms of precise timing than what old ...


9

The CRT itself is essentially a high voltage, high capacitance device on steroids and can hold a charge for well over a week. Touching the wrong contacts with your bare hands will throw you across the room or kill you. Years ago I discharged a 26" CRT - melted the ground wire (10 AWG) and about 2" of a screwdriver...right hand paralyzed for almost a week. I ...


9

Caveat: 'Why Not' questions are like 'What If' and rarely have a definite answer. It's an (educated) speculation at best. In case of interface and connectors, NIH (Not Invented Here) is a big issue. Beside the fact that adding more interfaces costs money, manufacturers usually love to have closed systems where they control - and most important sell all ...


9

TLDR: It's a soft spot for optimization around the ability to display 25 lines of text. (And why this is important has been discussed some time ago in an answer to your question about why 80x25 became standard) Preface: As usual with such decisions there are many factors involved - and most of them are not hard but variable within a certain frame and in ...


9

It was because I forgot to plug a jumper into a socket that switches it from a 240V AC input to 120V AC input (socket M5). I simply forgot to plug it in. That's not the ONLY thing I did wrong, but it's the one that mattered. Here's a complete list of ways in which I nubbed this up, for future readers benefit: I forgot the 120 V AC plug (see above) I tested ...


9

Isolating transformer won't help; the HV parts just have to be avoided when making the picture adjustments (mainly, that's not hard). All the red/green/blue circuitry is innocuous circa 50VDC stuff, on the cathode end of the picture tube neck, not as hazardous as the focus adjustment (which is an insulated control) to the only fat HV wire at the neck. None ...


8

That's an IBM PS/1 monitor. The large DB connector is used to give supply to the computer (which has not a power supply of itself). The monitor is VGA capable, so as long as you connect it to a VGA adapter and set it to 640x480 @60Hz, you are fine. The monitor can go down to 50Hz, and possible, up to 72Hz.


8

As others have said, Atari didn't recommend a monitor as far as I'm aware, but I can confirm S-Video on a Sony PVM looks fantastic. I remember as a kid my Dad telling me why he'd bought a Sony TV (a little 14" Trinitron) and him showing me the manual for Archon. Interestingly enough, EA did recommend a Sony ;)


8

Magnetic coils (the coils that magnetically deflect the electron beam in a CRT) have an electric resistance which is a direct function of the frequency of the current flow. If that resistance is getting too low (because the coils and circuitry are operated at a different frequency they are intended for), either the circuitry that regulates the current ...


8

There are basically two distinct "tell-tales" for electrolytic capacitor leakage: Bulging pressure release plates at the top of the capacitor, with possible signs of leakage emanating from there. Fishy odor. Absent both of those indicators, I'm inclined to think the staining of the PCB is from another source. Also, the electrolyte from the caps is highly ...


8

Sometime in 1980 (or maybe 1981) my school district purchased it's first batch of Apple II+ computers. The hardware our specific school district purchased consisted of Apple II+ computers, each with a single floppy disk drive and a small (maybe 8") black and white monitor. The only monitor Apple sold with the II series in 1980/81 was the Apple III Monitor. ...


8

Here's a Sanyo VM-4209 in a 1977 Apple II advertisement. It has a black handle on top (the VM-4509/DM 5109CX has a beige colored recessed handle): And another photo to show the color of the case better:


7

Fault you describe implies problem with electron ray sweeping... Triangle wave generator this circuitry is used for x and y sweeping across the screen area. If the shape is not triangular but curved it can create distortions like you describe. There are few common reasons what could cause it: electric fault of some kind like bad electrolyte capacitor, ...


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