How to build a composite video adapter
(for the Speccy's edge connector)
As our own little hardware project, at YSAC towers we decided to try to get composite video out of a 48K Spectrum (this won't work on 128K models as the composite signals on the connector are not available) via the edge connector. We obtained the necessary bits:
If you're thinking the edge connector looks too short, so were we. This was a slight (ahem) "schoolboy error" during the ordering process. The idea was to get one which fit over the wider part of the edge connector, the plastic casing on one side slotting into the gap and keeping it all lined up.
The connector which actually ended up with was half the size of that intended, but fortunately long enough to reach the vital pins 14 and 15, and the plastic edge too wide and offset to slot into the gap without being cut anyway, thereby requiring both sides to be cut:
Ideally a right-angled connection would have been used, but these weren't available in that size and ultimately the straight-edged one turned out fairly neat anyway.
At this point a multimeter was used to ensure the connector was lined up (none of the pins were shorting).
The second mistake was the composite port wasn't the right type to fit onto the stripboard, and had to be glued. The strips on the board where the edge connector fits on needed to be stripped off as well so nothing shorted (the intention being to solder all the pins to the board to keep it in place - this never happened)
Now all that was left to do was seat the edge connector on the board, and connect pin 14 on the bottom - counted from pin 1 at the far right of the Speccy (the gap is pin 5) - to composite ground (the outer part of the composite port), and pin 15 on the bottom to composite signal. Our soldering skills are apalling, but the necessary connections were made.
That's it! If your soldering skills are as bad as ours, use an entire roll of insulating tape to ensure none of the metal touches. Perhaps the whole thing ought to go in a box, but that wasn't on the original shopping list, so we just covered the whole thing with another roll of insulating tape.
Check the Spectrum is still working via RF, first without the adapter, then with it connected. Next comes the exciting bit: use the new composite port. Et voila! One composite-enabled Spectrum.