Williams Sinistar - Page 19

MORE DIAGNOSTIC MODE TESTS
TEST & PROCEDURES VIDEO SEQUENCES REMEDY OR ADJUSTMENT
REPLACE RAM 1B REPLACE RAM 2B
1) light red screen
2) red screen
3) dark red screen
too-light or
too-dark red
or grey band
magenta band
4) light green screen
5) green screen
6) dark green screen
yellow band cyan band
7) light blue screen
8) blue screen
magenta band too-light or too
-dark blue or
grey band
4) light green screen green band dark green band
or grey band
5) green screen light green band dark green band
or grey band
COLOUR RAM TEST
(Test 6)
Note that a blank sequence
or two sequences with the
same shade indicate a faulty 1A flip-flop, 1B RAM or 2B
RAM or a failure in the colour analogue circuit. Check
voltages on Q1 (green transistor), Q2 (red transistor) and
Q3 (blue transistor). During the eight full screen colour
tests, the base voltage (centre Pin) on each transistor
should vary between 3.8v (brightest colour) and 4.4v (no
colour)
Colour
RAM
check
(1) CRT sequences through 8
colours, 2 seconds each
(2) Thick vertical band
indicates colour RAM fault.
6) dark green screen - grey band
cross hatch pattern Aids you in setting up
vertical and
horizontal linearity, convergence and focus.
red screen
green screen
blue screen
colour bars
Aids you
in optimising colour purity
MONITOR & COLOUR RAM TEST
(Test 7)
MAGENTA
CYAN
YELLOW
WHITE
BLACK
BLUE
GREEN
RED
Colour Bar Pattern
colour bars
•
double-width
•
half-width
•
transposed
•
missing
If colour RAM test 6 indicates
no faults,
symptoms at left suggest a fault in 1A, 1B,
2B or 2C chips.