Memotech Limited MTX 500, Service Manual

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26
SYMPTOM 1
On power up:- No display or only a black and white
display.
a)
Cause of Trouble
Black and White output.
Check Point
Video Board
Oscillation of Xtal 4.433619Mhz or pin 17 of LM1889
IC47.
Repair Method
1 If pulse is present on P17 of LM1889 turn CVI
until oscillation is at its optimum pitch 3v
peek to peek. See fig no 1.
2 If pulse is absent LM1889 is faulty - or
associated circuitry.
b)
Cause of Trouble
Rapid Fading of colours.
Check Point
Tantalum Capacitor on 5v pin 2 of the modulator
Repair Method
1 Check Tantalum is a 22uf -Ve leg is earthed and
+ Ve leg is sufficiently soldered to the 5v pin
2 of Modulator.
2 If still faulty replace pal board.
MTX Service Manual