Heathkit H9 Manual page 38

P a se 3 6
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CONDITION
POSSIBLE CAUSE
9. -150 volts is incorrect.
1. D304.
2. c323.
10. +400 volts is incorrect.
1.
R335.
2.
D305 - D307.
3. c324 - c327.
VIDEO RELATED PROBLEMS
CONDITION
POSSIBLE CAUSE
1 1. No video (blank screen).
1. Anode voltage incorrect,
2. Grid voltages incorrect (G1, G2, G4).
3. No cathode drive.
4. Q308, Q309.
5. lC222A 1Viffi out of character generator circuit board).
6.
Videoiblanking chain on the character qenerator circuit board.
7. Brightness control R338 turned down.
8.
lC217A (blanking in).
12. Screen all white (raste|.
1.
Check grid voltages.
2.
Q308 or Q309 shorted.
3" tc222A.
4. Videoi blanking chain on the character generator circuit board.
5. Brightness control R338 turned up.
13. lnsufficient brightness or contrast.
1. Q308, Q309.
2. R342, R343.
3. C328, C329.
4. Check grid voltages.
14. A single bright horizontal line appears on the screen.
1. Vertical amplifier.
2.
Deflection yoke (vertical),
3.
Q301 - 0306.
4.
lC221A (V sync) on the character generator circuit board.
5. 1C216 (sync/frame counter) on the character generator circuit
board.
15. Too much or too little heioht. 1.
Height control R303 misadjusted.
2.
Q301, Q302.
3. C303 wrong value or installed backward.
16. Too much or to little width.
'1.
Adjust width jumper.
2.
C321.
3. Deflection yoke or 1301.
4. Flyback transformer T2.
17. No horizontal sync.
1. R325.
2 .
C 3 12 ,C 31 4.
3 . 1c 301 , l c 211 4.
18. No vertical sync.
1. lc221A.
2.
Q301.