Fluke PM6681 - Page 62

Trigger Level DAC’s
(Functional
Level
8)
Figure
5~20
Trigger level DACs,
U63 and U64.
Figure
5-21
Timing
diagram
for Trigger level
DAC’s.
A
sawtooth signal
of
approximately
12.5 Hz is generated
“
Run
the
DAC test, Test
9.
on
both the A
and
B trigger
levels. The sawtooth spans
—
Use test pin P5 to trigger
the
oscilloscope.
over the
complete trigger
level
range, and the B
value
equals the A
value
multiplied
by
-1.
This
means
that both
signals
can be
added
by using the
oscilloscopes ADD TRA-
CE function with
the result of
approximately zero.
“
Check
all signals
on U63 to U67.
NOTE: U3, and
U67 are located
at the bottom side of the PCA,
see
Figure
5-20
and
Figure
5-21.
“
Trace
the signal
from
U65 and U66
pin
6,
to TRIGGER
LEVEL
A and B OUT,
Pill pin 1 and
2
at
the
rear pa-
nel.
-
Connect
TRIGGER
LEVEL A
and B OUT to the oscillos-
cope and
check the
result
by
using the ADD
TRACE
function.
If
you find any
fault, continue
with
traditional troubleshoo-
ting techniques
and replace
defective circuits. See also
Chapter
4,
Circuit
Descriptions,
Trigger Level Circuits.
5-14
Troubleshooting