Tandy CM-4 User Manual

TROUBLESHOOTING
GUIDE
Circuits
checked:
• Power
regulator
circuit
•
Protector
circuit
•
Horizontal
sync
circuit
NO
POWER
Does
150V
appear between
the
anode
of
SCR701 and
ground?
Yes
Connect a
zener
diode (60V)
between
the
gate
of
SCR701
and
T702-to-D716
junction:
connect
the
zener
diode anode to the gate of
SCR701
.
Is
the power
circuit
activated?
i-
— —
-*
—
—
«
J
»«! D705
1
1
1
Yes
D716
i
i
i
No
Connect
a
resistor
(15W,
50
ohms)
between
TP-91
and
T702-to-D7
16
junction.
Is the horizontal
sync circuit
activated?
No
Yes
Does
18V
appear
between pin(S)of
IC701
and ground?
—
No
Yes
Does
7.8V appear
between
pin(7)of
IC701
and
ground?
—
No
|
R615
D605
)
IC601
R613
t\
Q601
R620
i
Q602
D603
I
D602
JR717
R719
D714i
|R716
D713
|
i
i
i
IC701
R706
*
R707
R709
!
R711 C707
Yes
SCR701
R712
R705
C709
C710
I
J
18

Tandy CM-4 Specifications

General

Brand	Tandy
Model	CM-4
Category	Monitor
Language	English