New Stuff For Old Stuff :: Blog

A fter watching this video from RMC I ordered some bits from ZXRenew; a new membrane keyboard and a couple of the modulator replacements. In the past I've used the ZX-CCB  and thought I'd try the ZXRenew Composite Modulator Replacement . I knew that in my box of ZX81 parts I had one with a duff keyboard. It didn't really need that label because the connectors had obviously cracked and crumbled.  Otherwise the case is in reasonable shape (the red ZX81 can be easily touched up). The board looks great. Most chips are in sockets and in the past I've obviously found the ULA to be good and heatsinked (heatsunk?) it. The other side of the board is a bit fluxy, but I think this is a 'bought assembled' one. The modulator was in good shape but pretty useless today. It's easy to remove it without damaging anything, and keep it somewhere safe.  Here's the replacement in place. The switches determine whether the circuitry adds the 'backporch' to the video si...

T he ZX81 was my first computer. Mine was screwed to a board with a terrible external keyboard, and I was proud of the fact that someone had fitted 2k of RAM. It was my introduction to BASIC and machine language. Let's not forget that the humble zeddy is a vehicle for a Z80 (which has 16-bit features) running at >3Mz. (Of course you can only harness that amazing power in fast mode, ie without display output, because much of the CPU time is usually used to generate the display.) Other than buying some kind of box that will convert the TV signal (with which I had limited success), it's possible to perform surgery to convert the output to composite, which modern displays may be more likely to display (but still maybe not in the case of the ZX81s with the older ULA). Here are three methods - rewiring (cost zero), using some simple components (cost pence) and a purchased modification (still less than a tenner.) With the newer issue 81 it's possible to simply tap the...