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2) Power ripple check
1.
Turn power off.
2.
Remove the
Logic Element
covet and
the power
assembly safety
cover.
DANGER: Primary voltage is present on power assembly.
3. Turn power on
and measure the ripple using
output connector pins of the power assembly
and Video
Elements should be
connected to
Ripple should be as follows:
oscilloscope at the
(Known good Keyboard
the
Logic Element) •
--,
I
Voltages
Scope Probe I Maximum Limit I
l-
+-
--I
I
+
5 Vdc
Pin 3
I
200 mV P-P
I
I
-I
I
-12 Vdc
Pin 4
240 mV P-P
I
I-
-I
I
+12 Vdc
Pin 2
See note
1
I
L~.--~~~.1..-~--~~-------"--~--~----------J
Note 1: Ripple
for
+12 Vdc
line
is
hard to· be
measured.
Instead
of
measuring
of
this
line
observe
the
displayed pattern.
Ripple problem of this
line will
cause the jittering of display.
If any ripple
does not meet the above
specif1cation, exchange the
power assembly.
• Scoping Procedure for Ripple
1&> ..............
···T···· ............... .
9o~--+-r-!--r-t-....--±-r-t-"'1""""1rr-t--t---i
~
t
1-
J.
10~~.-t-J-f.-'-!-""+..ic...+f'
........
t--"""-t--t--1
?········································
.
~
Displayed Voltage scale: 50 mV per cm
Turn scope power on.
Connect a
10: 1 (10X)
probe to CH
1
INPUT.
Set A Triggering Source to INT.
Set A Triggering Coupling to DC.
Set SWEEP MODE to AUTO TRIG.
Set TIME BASE to 5 MSEC/DIV.
Set MODE to CB 1.
Set CH
1
AC/GND/DC switch to GND.
Set CH
1
VOLTS/DIV to 5 MV.
Set POSITION,
tNTENSITY, and
FOCUS for
sharp
trace
in
the
center
of
display.
Connect the probe ground to Pin 6 of the
output. connector
pins of
the power
assembly.
(Use
the
short
ground
wire.)
Set CH
1
AC/GND/DC switch to AC.
•
Connect the probe to
the voltage pin to
be tested.
11/10/79
2-7a
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