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26Mar/190

VTech Socrates – Educational Video System

This poor unit was found in a box of random junk at the local tip shop. It's a VTech Socrates educational computer based of the Zilog Z80 chipset. It seems to have standard RF input/output, but someone has gone ahead and wired in their own antenna cable? The couldn't be bothered finding a screw-to-plug antenna adapter?

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After working out how to tune an analog signal on my TV, I applied 12v... A very slow screen started to appear! Is that Johnny-5?

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Giant Bomb's Review of the system doesn't give a favourable view. It seems that the unit had a 'very short life' due to slow graphics/animation and little software being available. It does mention the extra items, such as the mouse and touchpad... of which I've been unable to find physical examples of.

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The expandability is obvious in the above photos.. you can see the Cartridge slot and Expansion slot on either side of the motherboard.

Composite Mod

Just like most items that come across my workbench, I don't believe there's any need to keep them as RF-output. RF modulators were a requirement back in the day as TVs only had RF-antenna input. RF was fine for terrestrial signals, where a cable would be slightly inconvenient! Not so when the unit producing the a/v output was located right next to the TV. Once composite signals started appearing on TVs, there was absolutely no need to convert to-and-from RF. Of course, it was already too late for devices that only had RF output.

The RF modulation circuits in these units usually consist of a silver modulator unit and the inputs to this are more-or-less the exact composite signal required. Removing (or bypassing) the modulator is an easy step and RCA sockets can usually be installed somewhere in such units. Here's how to do it on a Famicom.

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Anyway, back to the Socrates. The original owner had already trashed the RF modulator, so I chose to remove it. The ribbon that runs to it is pretty hard to work with, but I spliced into it and ran the wires to RCA sockets instead. I provided both right and left audio plugs, but they're both wired to the same single mono audio output signal.

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From there, the picture was clean and crisp. The sound too! Of course, it's always hard to take photos of CRTs.. I tested it on the BeoVision MX 7000.

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And.. about that refresh rate... this was it trying to draw a spelling game over about 12 seconds...

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I was presented with R A I O D as a scambled word challenge...

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Nope.. it doesn't know what RAID-0 is.

Cartridges

A short time googling found me at Team Europe's blog post regarding the innards of a VTech Cartridge. How cute are they? Designed after a floppy drive, of which you jam in the side of the machine when it's turned off.

The insides look as simple as an EPROM on a board with a single capacitor? I was about to ask for the board pinout, as it seems there's one or two traces under the chip, but then I came across their post from this year regarding their multicart! Hah, it's exactly as expected... an EPROM on a very simple circuit board. They've used an EPROM that's 8x too large, to fit 8 images (all games ever produced) on the chip... you then select the start offset with the dipswitch.

I've sent out a message requesting one... let's hope they're still available!

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