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1 G
I
ENERAL
NFORMATION
Introduction
Principle of Operation
I
NTRODUCTION
The ZX Printer is designed for use with the Sinclair range of microcomputers, and provides a permanent
record of any computer output which may be displayed on the TV screen. Because graphic displays always
'join up', long programs, tables of results, elaborate patterns and graphs can be printed out as continuous
records, even if carried out in several parts.
P
O
RINCIPLE OF
PERATION
The printing mechanism is unconventional, and consists of two styli which pass successively across the
surface of the paper. Each pass represents one row of dots, and six rows of dots form the matrix for a
single line of print. A moderately high voltage (50V) is generated in the electronics within the printer, and
is routed to a conductor strip in the top cover.
Each stylus is hairpin-shaped so that one end passes over the surface of the paper whilst the other end
contacts the conductor strip, thus carrying the current to the natal lie coating of the paper. The return
path is through the coating to the conductive rubber roller, which also feeds the paper through the printer,
to the earth connections within the electronic circuitry. Before making contact with the paper, the stylus
passes over an 'L'-shaped insulating wafer; as the stylus leaves the wafer, it touches the paper and the
electrical continuity is sensed by the control electronics which then pulses the applied voltage to provide
the printing action.
A description of the control circuit is given in Section 2.
4
Sinclair ZX Spectrum Service Manual
Spectrum For Everyone https://spectrumforeveryone.com/
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