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3 F
D
AULT
IAGNOSIS AND
The following table is intended as a general guide to the diagnosis and rectification of most of the faults
which may occur after considerable usage of the printer.
Fault
1. Poor print quality:
a) Vertical zig-zag usually
worse on right-hand side.
b) Horizontal lines unevenly
spaced.
c)
Print fading out over part
of line
d) 'Noisy' printing
2. No print:
3. Motor not operating:
4. Motor running slowly:
5. Inadequate paper feed:
9
Sinclair ZX Spectrum Service Manual
Spectrum For Everyone https://spectrumforeveryone.com/
R
EPAIR
Possible Cause
a) Worn belt
b) Worn belt
c)
Dirt on conductor strip in
top cover
d) i) Excessive gain on TR5
ii) Insufficient signal from
encoder.
a) If print is all black, check
TR4.
b) If no image, check that
white wire is connected to
conductor strip.
c)
Dirt on photodiode and/or
LED.
d) Defective photodiode
and/or LED.
a) Conductor strip has
become loose in top
cover.
b) Motor bevel pinion
touching motor mounting
screws.
a) Excessive friction on
encoder disc.
b) Excessive gain on TR5.
a) Insufficient spring
pressure on paper pinch
roller
b) Paper reel ends jammed
against the cover.
Remedy
a) Fit new belt.
b) Fit new belt.
c)
Clean and lubricate
conductor strip – use
Electrolube.
d) i) Fit ZTX551 in place of
ZTX550
ii) Fit new ULA.
a) If defective, change TR4.
b) Connect white wire to
conductive strip and check
50V is present on strip.
c)
Clean photodiode and/or
LED.
d) Fit new photodiode
and/or LED.
a) Fit new top cover
assembly.
b) Check tightness of screws
and reset gear mesh (see
Figure 4).
a) Slightly slacken base insert
screw near encoder disc.
b) Fit ZTX551 in place of
ZTX550.
a) Fit new 0.60mm dia.
Springs.
b) Ensure that reel is wound
tightly and not touching
cover.
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