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9.4
The phototransistor TR9 is soldered to the board, while the LED is on
flying leads stuck into the base insert.
lot of tolerances but there should be greater than 200 mV p-p at pin 2
of the ULA when operating.
etched encoder disc, encoder disc working loose, incorrectly formed
slot m the base frame in front of the phototransistor (some have
metal shims with photo-etched slots) .
front of the phototransistor also give misleading results.
operation
oscilloscope probe on the emitter.
9.5
Transistor TR6 switches the motor on and off.
lines of an 'L print' the motor runs slowly; this is accomplished by
switching
conjunction with the phototransistor output.
9.6
The motor is fitted internally with a vanstor ring suppressor.
Without this it would generate so much interference to make it
unusable. It is unlikely, however, that this would occur.
of
transistor
TR9
TR6 on
and off,
These items are subject to a
Common faults encountered include, over-
Dirt in the encoder disc or in
can
be
readily checked using
using the time constant
2.4
During the last two
R13/C8
The
an
in
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