This article focuses primarily on because they are the most accessible—you can use a simple audio cable from your laptop to the Spectrum.
: Later models like the +2 used a modified System Test ROM that included a loop-back lead for testing RS232 and keypad sockets. The +3 has a built-in self-test activated by holding BREAK during reset, followed by the keys QAZMLP . zx spectrum test program link
It identifies specific faulty RAM chips by IC number, saving you from desoldering everything. This article focuses primarily on because they are
