Heathkit H9 - Page 38

Pase36
@
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.
C312,C314.
3. 1c301, lc2114.
18. No vertical
sync.
1. lc221A.
2.
Q301.