digital cassette recorder with the ZX81 - makes the storing of programs more reliable for Sinclair's smallest

In the May 1984 issue of Elektor we mentioned that connecting the digital cassette recorder described in January of this year to the output of a ZX 81 can cause problems. Since then we have worked day and night (in spirit at least) to find a solution to help owners of this computer. This article deals with what we came up with. digital cassette recorder with the ZX81 elektor september 1984 digital cassette recorder with the ZX81 A few changes are needed both to the cassette recorder board and the ZX 81 board and we will begin with the latter. Part of the circuit of the ZX 81 is shown in figure 1. The computer"s output signal must be amplified by making a new cassette output. This is done by connec- ting a 10 k resistor to the TV/TAPE output (pin 16) of ICI. All this means is soldering the resistor to R29 on the printed circuit board, as indicated by figure lb. The out- put signal then has an amplitude of 150 mVpp. The digital cassette recorder operates by driving the tape into sat...