Sinclair kits

(Sorry for the message on a dead thread - i've been catching up on an e-mail backlog.) I ordered two of the ZX81 kits from Zebra Systems in January - one to relive the ZX81 building experience (with a better soldering iron than I had 15 years ago), and one to keep around in kit form. I received the kits about 2 weeks after I placed the order. The ZX81 kits from Zebra are early (issue 1) releases of the ZX81, and include a UHF RF modulator. Video format is selectable between NTSC, PAL, and SECAM by changing a few resistors. There are different connections for the RF modulator marked marked USA, UK, and Fr on the board; however, the assembly instructions say to ignore these and connect the modulator to the UK and Fr connections. The RF output is approximately on UHF channel 33 in the US. In the Sinclair minimal cost tradition, the RF modulator is not crystal controlled and the output frequency tends to drift - a television tuner with adjustable fine tuning is a good thing to have. Alternately, you can pick off composite video before the RF modulator and use it to drive a monitor. Although the ZX81's video output is not particularly well suited for driving a 75 or 300 Ohm load, the picture is usable, and the addition of a single-transistor amplifier stage for impedance matching can provide reasonable composite video output. The supplied power supply has a 110 VAC input and outputs 9 VDC at 1A, so finding a replacement power supply for your local AC line voltage shouldn't be much of a problem. Zebra (or the tech school that Zebra bought the kits from) supplies their own instructions, which are geared towards assemblers in the US. The Sinclair instructions are not included. Assemblers in countries that use non-NTSC video standards will need to look at the schematic to determine the correct positions of a few resistors. Fortunately, the schematic diagram is included. The two books that are included with the kit ("BASIC Basics" and "Basic Basics of Basic BASIC", or something like that) aren't (in my opinion) useful for much other than pointing out some of the peculiarities of Sinclair BASIC. ZX81 kits were available in the USA by mail order ($149 kit, $199 assembled, IIRC) for about a year before Timex started selling assembled T/S 1000 machines here. Some other Sinclair-branded machines were sold in the US as well; I have US-spec ZX80, ZX81, and QL machines. The machines (that I know of) that were sold by Timex are as follows: Timex/Sinclair 1000 - 2K RAM version of the ZX81 Timex/Sinclair 1500 - 16K RAM version of the ZX81 in a rubber-key Spectrum case Timex/Sinclair 2068 - Enhanced 48K Spectrum with 3-voice sound, extended video modes, some weird bank switching logic, a cartridge port, and a joystick interface. Plastic keys and a space bar. Some of Timex's improvements supposedly made their way into the 128K Spectrum. There was also supposedly a Timex/Sinclair 2048 (not the same as the Timex Computer 2048), which, I assume, was a 2068 with less memory or fewer features. -- Scott Ware s-ware(a)nwu.edu