(date: 2024-12-08 07:05:12)
date: 2024-12-08, from: Old Ventage Computing Research
I still have my literal first home computer (the Tomy Tutor), and it so happens I also have my literal first game console: the Tandyvision One, Tandy Radio Shack’s label variant of the Mattel Intellivision Master Component.
Like my original Tutor, this is one system I’d never part with, so if I were going to make some tweaks to it this would be the unit. We’re going to do two mods in this article, neither particularly complex but nonetheless handy: composite video and sound outputs for improved quality and flexibility, and a power cycle hard reset button for convenience and less wear on the power switch. Some drilling and soldering required but not very much.
The Mattel Intellivision proper originally hails from 1978 and is notable for remaining supported and sold in three different decades (until 1990). Its development is explained well in many places, including by the Blue Sky Rangers themselves, so I’ll talk here mostly about the variants. Most of them looked like (and were) ordinary Master Components with different trim; for example, early units were manufactured by GTE Sylvania and GTE had a label variant of their own using silver inlays instead of Mattel standard gold, sold until around 1980. Probably the most “extreme” was the 1981 Sears Super Video Arcade, which had a rather different beige top case and detachable controllers, but was nevertheless manufactured by Mattel under contract using the same basic hardware and slightly different EXEC ROMs. The Super Video Arcade was especially notable because the prior Sears Video Arcade was an Atari 2600 VCS clone. Other variants from around this time include the 1982 Bandai Intellivision, also otherwise identical to a standard Master Component except for Japanese television channel tuning, and the Digiplay Intellivision (also sold as Digimed), which was manufactured by a Sharp subsidiary in Brazil due to that country’s then-protectionist policy against imported electronics.
Tandy’s particular spin was also later in the Inty’s lifecycle. In 1981 Mattel Electronics moved manufacturing to its own facilities in Hong Kong; by 1982 they were working on the “Big Mac” project that became the 1983 Intellivision II, a smaller and cheaper cost-reduced version. Tandy, always willing to label engineer first and innovate second (sometimes third, or tenth), made a deal with Mattel as OEM to rebadge some of the remaining O.G. Master Components and sell them in Radio Shack stores.
The console then appeared (“New for 83!”) in the 1983 general catalogue, billed as compatible with the Intellivision and Sears Super Video Arcade. By then, however, only 15 cartridges were specifically listed for sale; these ranged from $17.95 for Checkers to $29.95 for Astrosmash! or Snafu and $34.95 for Star Strike ($58 to $111). A separate “hotline” allowed people to order additional titles through their local Radio Shack, availability permitting, at no extra charge. Tandy did not attempt to rebadge any of these cartridges either, though some vendors like Parker Brothers explicitly listed the Tandyvision as compatible on some titles, and they do not appear to have ever sold the Intellivoice — or for that matter the doomed Keyboard Component, which by then was all but a distant memory.
We came by ours near the end of its run; we certainly wouldn’t have paid full price for it because money was tight in those days. Prior to this we had an Atari Ultra Pong Doubles, but I don’t consider it my “first” because we hardly played it as kids and its purchase predates my memory (it later broke and got thrown away). Instead, in 1983 the video game crash swept in with a bang and we were able to get the Tandyvision for substantially less than list. Plus, diving in the dollar game bins at Kaybee Toys gave us a huge library for pennies compared with what we would have paid during the Inty’s heyday. Even Mom played it somewhat, though Dad, myself and my sisters were the big users, and we had a lot of rotating family two-player games. I have many fond memories in particular of Triple Action, Snafu and Parker Brothers’ Frogger.
Though we were oblivious to it at the time, the video game crash caused Mattel console sales to plummet by nearly sixty percent and killed the Intellivision business unit, which Mattel eventually sold off to an investor group in 1984. As for Tandy, they sold their remaining stock until it was gone — ours was one of those — and then cancelled the product; it does not appear in any subsequent catalogue. Despite being arguably more powerful than some of the categorical computer systems Tandy sold then, it was never advertised in Radio Shack’s computer catalogues either.
Let’s finish talking about Inty variants briefly before we crack this one open. The Intellivision lived on after the 1983 crash in the form of the INTV Corporation, headed by a former Mattel senior VP, which bought the rights and existing stock for $20 million (about $61 million in 2024 dollars). When the existing inventory of Inty IIs ran out in 1985, sales were still decent, so the company resurrected the original Master Component in a cheaper form as the INTV System III (not to be confused with the unreleased Intellivision III). This unit came in black and silver, somewhat like the GTE Sylvania, but added an LED power light and omitted the front woodtrim paneling. Its controllers were in my opinion poorer quality, but by being based on the original model it could use off-the-shelf chips in stock instead of the custom consolidated logic chips in the II — we’ll talk about the chipset a little later on. INTV later rebadged the System III as the SuperPro System, but it was otherwise the same except for an unknown number of late units using the same upgraded hardware as the unreleased 1989 Tutorvision. INTV shifted to NES and Sega development as Inty sales dropped, but their licensing arrangements required them to discontinue the Intellivision in 1990 and the company went bankrupt in 1991. Near as I can determine, only Digiplay sold a non-Mattel version of the Intellivision II (in Brazil), and only Mattel ever offered the Entertainment Computer System.
This system went in storage for a number of years because its video chip started acting up and I got my Inty fix with a Sylvania Intellivision in the interim (my buddy was living in Santa Maria on the California Central Coast at the time and we found it for $cheap at a thrift store downtown, back when such finds were still possible). Later I added the Intellivoice from a VCF seller and the Cuttle Cart 3. The idea was always to repair it and I have spares in stock to pull from, but when I got it out of storage (prior to the robbery) it suddenly decided to start working again. In fact, it works perfectly now, just as it used to. I’m not sure why.
Anyway, let’s get started. There are six Phillips-head screws in the bottom case in the large recessed openings. Remove those and turn it over.
But wait! I hear you say. Doesn’t the Inty already have a reset button? Yes, it does, but we’re using a Cuttle Cart 3, which stores ROM images on an SD card and gives you an on-screen menu (pictures to follow). Once you select a game to play, then if you press the reset button by itself, it just resets that game exactly like the console would if an actual physical cartridge with that ROM were installed. To return to the menu requires holding down the CLEAR button as you reset, or power cycling. So, as a convenient alternative which also can double as a panic button, let’s add a button to the Tandyvision that acts like a power cycle.
The STIC, in fact, is what actually resets the system. Let’s consider the situation where the (existing) reset button is pressed, which is a switch connected to ground on one side and the STIC’s RSTIN pin on the other. This switch is normally open, so a pull-up resistor connects it to +5V. When RSTIN is grounded, this forces a reset, causing the STIC to automatically assert its MSYNC line. This line is wired to the corresponding MSYNC line on the CP1610 and the EXEC system, graphics and cartridge ROMs, resetting the CPU and putting them all into the same bus state. (This is necessary because the CP1600 and CP1610 multiplex their data and address lines, so the ROMs and the CPU need to all agree on which state the bus is in; the system RAM has special separate handling for this.) The CPU then starts executing the startup sequence from $1000 in the EXEC ROM.
The power-on situation is similar. In NTSC systems like this one, clock signals are generated by an AY-3-8915 Color Processor off a 7.15909MHz crystal (divided down by two for the 3.579545MHz NTSC colourburst and four for each phase of the two-phase system clock at 1.7897725MHz, yielding an effective CPU speed of 894.88625kHz); PAL systems use a discrete clock and colour circuit with a PAL STIC and 4MHz crystal for a 2MHz system clock (1MHz CPU). Clock generation occurs immediately with power. When the STIC starts getting clock signals after power on, it will also assert MSYNC and reset the system. The startup sequence continues from there.
Because of all these voltages running around, a momentary interruption on any one of the stepped-down power lines is not enough to trigger a reset, which is why the power switch cuts them all. The only one that when interrupted can break every power circuit by itself is the single ground/earth wire to the power supply board, which is the green wire with a faint yellow stripe. That’s the one we’ll cut. You’ll note that there is a tangent point in the wire bundle curve where it touches the bottom case, so we’ll install a button there, then cut, strip and connect the two halves of the ground line.
For the button we will use a momentary off switch (i.e., the button switch is normally closed and pressing it opens the circuit). This particular button was very handy because it has little holes that fit the wire, so it was just a matter of threading them through, making sure the two sides were separated, and crimping it down. No soldering needed.
This particular button is also secured by a screw-on collar that attaches from the front, so the hole we make in the case needs to be big enough to allow the button to stick out from the inside but smaller than its largest diametre. I drilled a small pilot hole and then got a bigger bit to ream out the hole. There was already a scuff on the bottom case; I didn’t do that with the drill, I swear.
Now for our second modification, which is a bit more involved: composite audio and video outputs. This is a very common modification and the overall process should work similarly for PAL and Bandai NTSC units. Essentially, we’ll use a small circuit to tap the video and audio signals to the RF modulator but adjust the video impedance to a typical 75 ohm composite output, and then run the signals out to external connectors. This is the basic notion.
The US FCC was very strict about shielding and radio emissions in 1978, so on the original Master Component everything apart from the power circuit lives in a shielded submodule called the logic board assembly. (This was not the case for the Intellivision II, which further helped it to be cheaper.) This submodule is in fact soldered shut for even less RF leakage, with just a few holes for the channel selector, RF out, screw mounts and reset button. Since this mod unavoidably involves some permanent modification to the logic board, even of a minor sort, I decided to do it on a separate known good logic board assembly I had on the shelf from another machine (another Tandyvision, as it happens). That way if I screwed it up, at least I wasn’t doing it to the original assembly from my real machine. Plus, I still don’t know why the STIC chip in my original console decided to pull a Lazarus, while this replacement one was unlikely to require service anytime soon.
To get into it, remove the screws holding the controller tray and take the tray out, disconnect the power ribbon cable and the blue jumper cable next to it, carefully unplug the controllers (note their orientation — there are a lot of fine wires!) and then lift out the entire submodule from the bottom case. Fortunately, the age of the solder even on this obviously newer unit is such that a good tug with a metal spatula will break most of the joins cold (I only had to heat up a couple). The “top” we are opening here is actually the bottom, so turn it over and remove the metal shield when the joins are open.
On the lower half, again starting at the left, we see the 5-pin power connector ribbon and the blue jumper wire. This wire crosses the 7.16MHz crystal and the AY-3-8915 Color Processor which would be replaced with a simpler clock circuit here and a 4MHz crystal elsewhere in PAL units. The two 2114-type RAMs at U12A and U12B are again replacements for another 256-byte GTE 3539 used as CPU-exclusive “scratchpad RAM,” and the two large chips marked “ROM” next to it are the RO-3-9504 and RO-3-9502 halves of the EXEC ROM (part of it is also in the 9503 GROM and copied to RAM on startup). Finally, an ASTEC UM1285 RF modulator is at the bottom, or a UM1287 in PAL units, and to the left of that is the prong for the channel 3/4 switch.
The circuit for converting the audio and video is all discrete components and not very complicated, and even a butterfingered idiot like me could probably build it on perf board. However, I found this nice little tiny SMT version on eBay (not affiliated, just satisfied), which gave me an idea: while most comp mods for the Inty run the wires out to a board outside of the submodule, this was small enough I could fit it all inside the logic board assembly and just have wires run to the ports. This wouldn’t likely make much difference to the video quality but I liked it being a bit more self-contained.
The circuit requires its own +5V and ground, plus the video and audio signals going into the RF modulator. These signals are carried on the wire closest to the RF modulator’s RCA jack (video) and two back from that (audio). The others are the RF modulator’s +12V supply and the channel selector. (There are now some kits that use this +12V line and step it down to +5V, but this particular board doesn’t have a voltage regulator.)
For the power connection, however, I didn’t want those waving around and shorting anything, especially since I decided I would take power directly from the ribbon connector. These wires are thus soldered in position. I chose to use green wires all the way through to indicate connections to ground, so the green wire taps the incoming ground line from the power supply board, and the yellow wire taps +5V. I buzzed everything out with the continuity tester and got good continuity with no shorts.
The wires on the other end of the new circuit board are video, audio and a single ground, which I split into two. I ran these wires out of the pre-existing hole next to the RF RCA jack and closed up the submodule (it doesn’t need to be soldered shut).
Unlike the button, the new RCA jacks’ screw-on collars go on the back. I took off the little sleeve rings and soldered them to the green ground wires, then selected bits for both the pilot hole and main hole. Here we will insert them from the front, so the bit for the main hole needs to be sized appropriately to be larger than the body of the jack but smaller than the front flange.
Before putting them in, I plugged in the power ribbon and blue jumper and did a quick video test. These RCA jacks have a little crevice for the plug tip and the sleeve rings just slip on. (Yes, that’s a Radio Shack cable plugged into it; it seemed appropriate.) I’ll show you grabs from the video in a minute, but I was very pleased with the output.
Many of the comp mods out there chose to install their jacks in the gap under the power supply board (i.e., the left corner of the unit) near the power cord, but that didn’t seem like a great place to run a video signal. Instead, I decided to put the holes in the right corner near the cartridge port, since the wires are thin and can route easily there. I was very careful to keep the pilot holes level with each other so we’d have a nicely aligned pair of connectors. I’ve seen a version of this mod that hooks a 3D-printed set of ports into the cooling vents, but that seems a little clunky to me personally.
Installed. I chose the red jack for the video signal.
The green wires with the ground sleeve loops easily reach the jacks, but I had to solder extensions onto the orange video and audio wires. These jacks come with an insulating washer that goes between the collar and the sleeve loop, so I put that on next, and then cinched the collars down tight. I then looped the signal wires into the tip crevices. The wires stayed nicely in position. Everything can be easily dismantled and reassembled if I need to get back into the logic board assembly.
Full video and audio test through the line input on my CRT games TV. It looks great!
I reattached the controllers (they aren’t keyed and while you probably won’t blow up the unit if you misalign the connectors, the controller(s) won’t work if you do), screwed back in the tray on top of the submodule, and made sure the controller strain relief blocks were in their little divots before putting the top case back on. Finally, after putting the screws in the back, I plunked the glamour cap back on the power switch.
Reassembled and functional in its new place of honour where the GTE Sylvania Inty used to be. Don’t worry, I’m not getting rid of it. I had a lot of fun with the Sylvie and I may find another TV to hook it up to.
Here’s an unretouched grab of the output on my Inogeni composite capture box. The colours aren’t as saturated as they are on the TV but that’s probably just something about the way the TV is adjusted. Otherwise, it’s nice and crisp and has just about no noise at all.
How does this compare with the RF output? Let’s take the TV grab from my article on an Intellivision reimplementation using an NES-on-a-chip. This grab was done with the Sylvie, but the Sylvie has an RF modulator that’s nearly as good as this one. The Inogeni VGA box grabbed it while connected to an LCDT600 to display the RF signal and I’m not sure if that’s why the top of the screen has that red shift, though the colours are otherwise nice and there is relatively little ghosting.
But the composite output, even though the colours are a bit muted, has hardly any ghosting.
Plus, the RF jack is still live, so I can display a picture on RF and composite video at the same time.
So I decided to keep it that way, just like he left it. You know, in case he ever drops by for a game of Biplanes or something. I’ll even let him win.
https://oldvcr.blogspot.com/2024/12/composite-and-hard-reset-mods-for.html
date: 2024-12-07, from: Richard Murray’s blog
SimpleSeq v0.24, Tea v0.18, Pushy collectors, Fascinating corona, Sombralyssia and the Tilley Lamp.
https://heyrick.eu/blog/index.php?diary=20241207
date: 2024-12-07, from: Hubersn RISC OS blog
Seit Ende Oktober gibt es ein neues Release (v3, wie sie mancherorts genannt wird) von RISC OS Direct, basierend auf der aktuellen „unstable“-Entwicklungsversion von RISC OS 5.31. Eine Weile war das etwas aufwändiger in der Installation – man musste erst mal das v2-Image auf eine microSD-Karte bringen, obwohl die RISC OS-Partition nur knapp 8 GiB groß war war die Image-Datei leider so groß, dass man normalerweise eine 32GB-Karte brauchte, und dann musste man davon booten … Read More →
http://riscosblog.huber-net.de/2024/12/risc-os-direct-5-31/
date: 2024-12-07, from: Icon Bar, RISC OS News
Big Ben has announced that their RISC OS eXperience will be taking place again in 2025.
http://www.iconbar.com/comments/rss/news2142.html
date: 2024-12-07, from: Hubersn RISC OS blog
Lange nichts mehr gebloggt zum Thema RISC OS – insofern ist das „jetzt“ im Titel relativ zu sehen. Bevor ich die 1,5 Jahre Pause aufarbeite, dachte ich, es sei nur fair, wenn ich erst mal das Pilling-Triple vollende. Drei Blog-Posts in Folge (die ursprüngliche „Freigeben als Open Source“-Meldung, dann das Open Source-Release von SparkFS, jetzt der aktuelle Artikel) rund um die Software des vermutlich produktivsten Entwicklers der RISC OS-Szene – niemand hat das mehr verdient … Read More →
http://riscosblog.huber-net.de/2024/12/ovation-pro-ist-jetzt-open-source/
date: 2024-12-07, from: Computer ads from the Past
Some computer related levity from OZ
https://computeradsfromthepast.substack.com/p/comics-from-198512-australian-personal
date: 2024-12-06, from: Digital Antiquarian
For some of you, Andrew Plotkin will need no introduction. The rest of you ought to know that he’s quite an amazing guy, easily one of the half-dozen most important figures in the history of post-Infocom interactive fiction. By my best reckoning, he’s written an even dozen fully realized, polished text adventures in all, from […]
https://www.filfre.net/2024/12/a-conversation-with-andrew-plotkin/
date: 2024-12-06, from: Computer ads from the Past
This British inventor speaks about his ZX-80 computer system.
https://computeradsfromthepast.substack.com/p/creative-computing-magazine-interviews
date: 2024-12-06, from: RiscOS Story
And there’s now a beta version of the Impression User Manual in Bound format Chris Hall has made available a new version of RingBind. The application offers an alternative way to view user manuals and other publications on screen, making them look like ring-bound manuals, as though open on your desk – provided they have first been converted to the Bound format (and file-type). With version 0.20, a few bugs have been corrected, and the software now correctly implements page-to-page links – so rather than thumb (in a virtual manner)…
https://www.riscository.com/2024/ringbind-version-0-20/
date: 2024-12-06, from: Icon Bar, RISC OS News
TIB now has a social media account on Bluesky!
http://www.iconbar.com/comments/rss/news2137.html
date: 2024-12-06, from: Icon Bar, RISC OS News
Archive Magazine 27:3 was released this week.
http://www.iconbar.com/comments/rss/news2140.html
date: 2024-12-04, from: Linux Magazine
Just in time for the holidays, the developer of the Cinnamon desktop has shipped a new release to help spice up your eggnog with new features and a new look.
http://www.linux-magazine.com/Online/News/Latest-Cinnamon-Desktop-Releases-with-a-Bold-New-Look
date: 2024-12-03, from: Linux Magazine
If you’ve been waiting for Armbian to support OrangePi 5 Max and Radxa ROCK 5B+, the wait is over.
http://www.linux-magazine.com/Online/News/Armbian-24.11-Released-with-Expanded-Hardware-Support
date: 2024-12-03, from: Linux Magazine
SUSE has been a very powerful player in the European market, but it knows it must branch out to gain serious traction. Will a name change do the trick?
http://www.linux-magazine.com/Online/News/SUSE-Renames-Several-Products-for-Better-Name-Recognition
date: 2024-12-02, from: Icon Bar, RISC OS News
Archive 27:3 has landed in our inbox and should be landing on your doormats shortly… Let us know when you hear the thud!
http://www.iconbar.com/comments/rss/news2138.html
date: 2024-12-02, from: Icon Bar, RISC OS News
The December 2024 WROCC talk is on wednesday. As usual it takes place on Zoom and kicks off at 7.45pm.
http://www.iconbar.com/comments/rss/news2134.html
date: 2024-12-01, from: Richard Murray’s blog
Advent Calendars 2024, It was the other man, Poor Celebrations, Stew pizza, Advertising fail, Lidl air fryer, Composing music.
https://heyrick.eu/blog/index.php?diary=20241201
date: 2024-12-01, from: Icon Bar, RISC OS News
Many thanks to David Pitt for kicking off our 2024 Advent Calendar with some festive fun (It’s not too late to send us yours). David says “For a little festive fun how about a Christmas tree for the Taskmanager icon bar icon.” Absolutely!
http://www.iconbar.com/comments/rss/news2133.html
date: 2024-12-01, from: Computer ads from the Past
The Gold Standard
https://computeradsfromthepast.substack.com/p/maxells-mf-2-dd-floppies