-“-“-“-“-”
;
A5 IF ASSEMBLY
-m--m----
RESOLUTION
BANDW I OTH
I
10.7 MHz
IF ADJ OFF
EANDWI DTH
(WHITE)
1
---------------
J
I
CAL OSC
I
+lV
DC
L---------,
IF ADJ OFF
w54
DISCONNECTED
J3
+-is-
I
ILINEAR

j+J-

D-

w54
J4
,‘-,
J
LOG
I
u
(RED)
)
?
IWITH COUNTER ON
I
BURSTS OF 5.35 MHz
I
APPROX 10 mSEC 5
VP-P
I
w53
IJ5
(-)
I
/,
!
lyL
(BROWN)
w55
J6
A
I
L.&
(WHITE/
)
I
BLUE)
I
, A4 LOG AMP/CAL OSC ASSEMBLY
1
.---m---------------
W27

w

(ORANGE) SK171
Figure 9-2. IF Section Troubleshooting with the TAM
Both the digital control and DACs are multiplexed onto test point “channels” through
resistive networks. One DAC from each of the quad-DAC packages feeds into a network.
The TAM varies each DAC individually to isolate which ones failed. Similarly, 10
digitally-controlled lines feed into a network and are monitored by the TAM. The channels
used to monitor the DACs are listed below:
Channel A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A5J9
pin 1
(MSl)
Channel B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A5J9 pin 3 (MS3)
Channel C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A5J9 pin 4 (MS4)
Channel D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A5J9
pin 2 (MS2)
1.
On the HP 85623 spectrum analyzer, press
(PRESET),
MOIIULE
, and Diagnose. Select
Cal
fist
Troubleshooting Nude.
2. On the HP 85623 spectrum analyzer, disconnect W27 (coax 3) from
A5J5
and monitor the
output of A5J5 with a second spectrum analyzer.
IF Section 9-7