Video Problems; Wrong Color; Rgb Problem - Tandy 26-3334 Service Manual

6.2 Video Problems
1)
No
Display/No Sync/Noisy Video
•
Check Cable and Cable Connection
•
Check Power Supply and Transistor
Bias
Voltage
(Q2, Q3)
•
NTSC:
Check Video Signal
at
TP6
PAL: Check Video Signal
at
CVIDEO
OUT of CN8
*Before proceeding
next check, load
Diagnostic Program Pak (Color
Bar)
or run the
program below
•
Check Video Signal
at
Emitter
of
Q3 and check C67
•
Check Video Signal
at
Emitter
of
Q2 and check C54
•
Check Video level
at
TP7
(Waveform
1)
•
PAL:
Check Sync Signal
at
Collec-
tor of Qll (Waveform
16)
•
PAL: Check
the items
in 5)
RGB
Problem
10
'**COLOR BAR TEST**
30
ON BRK GOTO
1000
40
HSCREEN
2
50
GOSUB
500
100
FOR
R=0 TO
7
110
HCOLOR R,8
120
HLINE(R*40,0)-((R+1)*40,192),
FSET,BF
130
NEXT
R
140
GOTO
140
*500 DATA 63,36,31,18
*510 DATA 9,7,11,0
520
FOR X=0
TO
7
530
READ A(X):NEXT X
540
FOR
R=0 TO
7
550
PALETTE R,A(R):NEXT R
560
RETURN
1000
PALETTE
CMP:
END
*
For PAL
500
DATA 63,54,27,18
510
DATA 45,36,9,0
2)
Wrong Color
•
Check Video Signal
(TP7) and Chroma
level (Waveforms
1
and
2)
•
Adjust
TV
control
3)
Ho Color
•
Check Video Signal
at TP6 (PAL:
CVIDEO OUT of CN8) and Color Burst
Signal (Waveform
2)
4)
Random Character/Clear Screen/No
Sign-on
•
Check RAS*
(TP4),
CAS*
(TP5)
•
Check pin
1
and pin
2
of IC15
•
Check pin
20 of IC2
•
Check IC16
-19 (Dynamic RAM)
•
Check
the items
in
6.4
Processing
Problem
5)
RGB Problem
•
Check
Red, Green, Blue Signal
(Waveforms
3
through
5)
using
Program Pak or Test program
below
•
Check HSYNC, VSYNC (Waveform
6)
10
'RGB
LEVEL CHECK
11
**COLOR-D* 4/3/1986
20 PALETTE RGB
30
ON BRK GOTO 1000
40
HSCREEN
2
50
GOSUB 500
100
FOR
R=0 TO
15
110
HCOLOR R,0
120
HLINE(R*20,0)-((R+l)*20,
192),
PSET,BF
130 NEXT
R
140
GOTO
140
*500 DATA 63,54,27,36
*510 DATA 18,9,32,16
*520 DATA 8,4,2,1
*530 DATA 45,40,5,0
535
DIM
A(16)
540
FOR X=0 TO
15
550
READ A(X):NEXT X
560
FOR
R=0 TO
15
570 PALETTE
R,A(R):NEXT
R
580 RETURN
1000
PALETTE
CMP:
END
For PAL
500
DATA 63,54,27,18
510
DATA 45,36,9,0
520
DATA 56,48,24,16
530
DATA 40,32,8,7
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