Monday, 8 September 2014

RAM Cartridge for the Yamaha DX7 Synthesizer (Part II: Prototyping)

You knew it! If you followed my Les Paul DIY build log, you're not surprised to hear that I managed to bungle the DX7 cartridge project in a similarly spectacular fashion, and it's all my fault.

The prototype boards arrived, and they look awesome! The PCB material is of a dark violet color, and all the solder pads are golden. I ordered them at OSH Park, where you'll always get (multiples of) 3 boards.

DX7 cartridge prototype boards, rightmost already populated.
When I checked them I saw instantly that I made the connector part too small. Instead of measuring the proper connector spacing, I violated Sommerer's Law ("your assumptions are wrong") and assumed them to be the usual one tenth of an inch or 2.54mm. Well, its closer to 3 mm, so they don't fit. Oh, well!

Now, instead of throwing them away and order another batch with the proper dimensions, I'll use them as tinkering material. I already ordered a small sheet of blank double sided circuit board, which I'll cut to size using a high-tech template that I made from an obsolete phone card.

I'll make the properly spaced connector traces by filing or scratching gaps into the copper layer, and then glue the contraption as a new connector onto the PCB. All that's needed then is pieces of wire connecting the pads on the cartridge PCB with the corresponding pads on the new connector. It'll look hideous, but serve its purpose.

But first I have to wait for the blank PCB to arrive.

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