1.37″ CRT Restored By Hacklab For Miniature MAME Cabinet

For $5, [William] of Toronto’s Hacklab hackerspace got a hold of one of the smallest CRT screens ever made – about the size of a large coin. Over the course of a couple sessions – including a public hack boothside at their Mini Makerfaire – [William], [Igor], and several other members managed to connect it as a monitor directly off a Raspberry Pi. The end-goal is the world’s smallest MAME cabinet (smaller by almost half than this LCD one).

As Canada followed the US and stopped broadcasting analog back in 2011, it became quite a challenge to feed the screen a video source. They disclosed early that the easiest solution would just be an RF transmitter on the Pi and then tune the micro-set to that channel. Too easy. They wanted something elegant and challenging so they went digging into the circuitry to find a place to insert a composite video signal directly.

The real story here is their persistence at reverse engineering. The PCB was folded like a cardboard box to fit in the original case, making large portions of the circuitboard and wiring inaccessible. Even when they managed to trace the signal to what they thought was the appropriate chip (marked C80580), they could not find any information on the 30 year old chip. Noting that every other chip on the board was Panasonic and started with “AN5”, [Igor] suspected the mystery silicon was just renamed and went through every single datasheet he could find with that prefix. Combined with form factor, pin count and purpose, his sleuthing was rewarded with a guess for a match – the AN5715. His hunch was correct – using that datasheet led him to the answers they required.

Then they just had to figure out how get the composite signal the Pi outputted into something the chip would use to display the correct image. There were no shortage of challenges, failures and dead ends here either, but they had help from the rest of their membership.

Their project log is an interesting narrative through the process and in the end of course, it worked. It is displayed beautifully with a clear acrylic case and ready for a cabinet to be built.

27 thoughts on “1.37″ CRT Restored By Hacklab For Miniature MAME Cabinet

    1. yeah, should use a tube for an old video camera viewfinder….

      but really the small screen isn’t great unless you’re doing something portable

      maybe a “computer for ants” with the crt would be cool, but not really in any more than a novelty

      might also be cool to try and make a computer terminal like in “Brazil” with a fresnel lens in front of a small crt and some kind of teletype or typewriter keyboard

    2. Ahahaha, I did an image search and this TV actually had a lens accessory so you could see it. That is really bad/funny when you know people can’t even see your product so you bundle a magnifier. Apple should do the same with reading glasses, all the grannies around have the silly (tiny) iPhones and can’t see the darn things

  1. The most incongruous thing in these small device builds is the size of the wires and connectors. We all need new families of affordable smaller cables and connectors. I most definitely would like a much smaller Ethernet connector and cable, for example. Check out old Bell System tinsel wire for fine wires that will not break from bending – fine stranded wire wound spiral on a latex core and used int he coiled handset and phone extension cords. A modernized version of that would be a good start.

    1. Time to go wireless, the tinsel wire was half the noise on old landlines. Micro USB is a poor connector, the mini is much more reliable. Wet spaghetti cords are designer BS destined for the can. If it ain’t tough’ it’s wimpy crap.

    1. I had fun once with a vidicon cam and CRT viewfinder combo, adjusting everything at both ends. Different aspect ratios, frame rates as well as all the distortions seen on what passes for TV now.
      How about pre-war British TV with 400 lines but in ultra-widescreen!
      It was a camera from the 1/2 inch RTR era. The CRT was about a whole inch or more.
      It would be quite a hack to mod a big TV to display some of these “alternate world” versions of this TV camera.

  2. I have a little 1/2″ viewfinder crt. I flipped the x deflection coils (was made to be viewed in a mirror) and glued a small magnet on to center the image, and hooked it up to a plug and play. Pacman was very hard, but not impossible to play. Forget Xevious. Mappy was still pretty fun.

    I also bought a bunch of old 4″-9″ tvs from goodwill for $2-$6 each. Most of them had no video input, so I just probed around with a scope on all the chips until I found the pin with all the static, cut the trace, and injected my own video signal. Not fool proof, but it got the job done in ten minutes.

    1. Wished my local Goodwill still carried small TVs. They no longer accept any TV that is more than 1″ thick so I don’t have a source of small CRT TVs, just from tiny viewfinder CRT in camera they still sells.

      1. Hello, another one from the present day lurking here in the misty past…

        Check out the Entex Adventurevision. An expensive portable games console from the 1980s. Didn’t use a Nipkow disk, instead used a column of 40 red LEDs, with a vibrating mirror. Same method the Nintendo Virtual Boy used a few years later. But it’s still an electromechanical monitor, just scanning 40 lights in this case instead of 1.

        There were only, I think, 4 games released for it. Until recently, when somebody wrote some homebrew software. It’s a niche market, for a console almost nobody could afford back then. It’s a shame cos I’d love one. They’re just so damn nifty! Maybe I’ll try the emulator and realise the games are all awful. Hope so!

  3. This is why I like going to Goodwill and Salvation Army. Now and then they have old video camera with viewfinder and quite often for under $5. Lots of spare parts in the camera as well some that I can maybe use. B&W CRT are fairly easy to deal with, most of what I got only used 3 lines to the mainboard: ground, 5v, and composite.

    Color viewfinder is very hard to find as most went with small LCD instead of CRT but I did get one. Still haven’t figured that one out yet as the chip were unmarked and there’s 8 wires, guessing RGBHV plus power and 2 ground.

  4. Understanding back in the day TV CRTs where remanufactured, the “CRT Restored” in the title lead me to believe I was going see that someone restore the actual CRT, not hack the appliance the CRT was mounted in.

    1. Yeah, I remember in the back of Radio-Electronics magazine they used to advertise equipment for rebuilding CRTs.
      I have a REM picture tube restorer. It was better than most restorets, because the “Rejuvenate” function was slower and you could monitor the cathode emission while rejuvenating it. If the emission started to drop, it was time to stop.
      Other devices the Rejuvenate function just blasted the cathode, and often ruined it.

  5. Once upon a time, they had digital to photographic slide copiers – Polaroid made some I think. They had small CRTs with very high resolution – when some of us were still using EGA, these things were over 1000 pixels vertically; ISTR some at up to 4000! If you could find one of those it would be an awesome tiny high-res display. I don’t know if they were digital or analog input.

    1. The Polaroid Palette. I wrote driver software for them in 1987-1988. They were a true film recorder with a mono CRT and a filter wheel. Early ones were CGA resolution, later ones EGA. They used an ingenious interlacing scheme to double the vertical resolution.

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