2.6 Fault-Finding Guide
As with any complex digital equipment the possible fault permutations
are vast, thus the following table is not intended to be an exhaustive
list
of the
faults
that
might
occur
on the
Spectrum.
It is
intended
as a
guide only
to
possible courses
of
action
to
follow when
faults
show
up in
particular
areas
of the
circuit.
These
areas
are
listed
in
the table with sub-headings, in no particular order of priority. It is
envisaged
that
the
ZXTP
test
tape
has
been
loaded,
or an
attempt
has
been made to load the tape, in order to check for a faulty condition.
AREA SYMPTOM ACTION
TV screen dead, TR4 base-collector Remove TR4
smoke appears on shorted.
switch-on.
Short
persists
with
1.
Check
TR5 and
C44.
TR4 removed. 2. Visually check track.
3. Check TR4.
TR4 blows again. 1. Change TR4 and TR5 (even
though TR5 checks out).
2.
Check
that
TR5
circuit
components
are to
latest
specification.
Not initialising. No '(C)1982 Follow fault-finding
Sine!air. Research procedure, paragraph 2.2
Ltd1 statement. ^above. ' y y y
No video. No video. 1. Change IC1.
2. Check TR1 and TR2.
NOTE:
Table
4.1 No
video after
1.
Visually
check
IC1 and
sets out typical ULA changed. socket,
signals found on 3. Check for shorting
IC14 pins 1-18 between C65 and R53.
IC14 pins 1-18. 4. Carry out fault-finding
procedure,para 2.2 above.
1. Check voltage drop across
R64.
2. Check +5V regulator 0/P
and +9V regulator I/P.
3. Check PWR socket not
shorted.
4. Check power unit.
To Next Page
Loading...
