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A project log for Bad Apple on a Breadboard

Playing the "Bad Apple!!" demo video using a custom breadboard circuit made out of standard logic chips, with no CPU

George FootGeorge Foot 09/18/2020 at 21:120 Comments

So after a very long hiatus, during which this project was mothballed and put in storage, I've started to get around to writing up how this works!

In order to do that I've reunited the various parts, including some that I'd scavenged for use in other projects.  I also found that I'd forgotten to take detailed photographs before disassembling, and lacking an up-to-date schematic, that made putting it back together a risky business.

There was just enough wiring visible in some of my YouTube videos for me to figure out roughly where things went, and luckily when I plugged it into the TV, it worked just like it used to!

This was certainly a surprise - I had at least been expecting the EPROM to have degraded, as it has no UV protection at all.  But it seems fine.

As a result I've been able to reverse-engineer some schematics (PDF attached), which are also in the gallery if you prefer to browse them as images.  These cover everything on the breadboards, principally the video output circuitry (PAL composite output, with the right timings, sync pulses, serrations, etc) and the Bad Apple video stream decompressor/decoder.

Hopefully I'll soon add some documentation on how the whole thing works - but in the meantime, do let me know if you have any questions about the schematics or the circuit, I'm always happy to explain!

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