Master Series Service Manual
Does it only occur on one of the video outputs?
1 Is the CSYNC polarity link LK5 correct for your monitor?
2 If it only occurs on composite video, check that all the resistors (
R147 to R150 inclusive) to the output transistors are correct in
accordance with the circuit diagram. Do they all have good signals
going into them?
3) If it only occurs on UHF, check the signal as it passes through the
resistor network, IC40 pins 12 to 19 inclusive through resistors R69
75 77 78 84 85 87 and 89.
7.3.3 There is no colour on UHF.
1 Is the variable capacitor VC2 set to give the correct frequency of
17.7345MHz at IC43 pin 12?
2 Check connection to IC40 pin 11, and resistor summing node through
Li and C81 Q12 c88 and R140.
3 Check +5V supply on IC40 pin 20.
4 Try replacing IC40 as a last resort.
7.3.4 There is only one colour.
On RGB
1 Check the RGB connections out of the VIDPROC IC42 pins 14 12 and 10.
2 If the fault is only in mode 7 or 135 then check RGB connections
from SAA5050 IC32 pins 24 23 and 22 to the VIDPROC IC42 pins 13 11 and
9.
On UHF
1 Check RGB inputs to IC40 pins 6 7 and 8. If there are any faults,
check the connections from the VIDPROC IC42 pins 14 12 and 10. If any
nodes are stuck at +5V or ground then check for shorts. As a last
resort, try changing chips.
2 Check resistors R69 75 77 78 84 85 87 89 90 for the correct values
and that they have good signal levels at their IC40 ends.
7.3.5 The screen displays the wrong colours.
1 Check 1 and 2 above.
39
Issue 1
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