HP 3478A Technical Manual page 84

3478A 3478A
the A/D Controller (U462) is good. the A/D Cont roller (U462) is good. Go to paragraph
7-C-24 to check U462. 7-C-24 to check U462.
5. 5. If the v If the voltage is good oltage is good, connect p
of U201 (U102 pin 6 to pin of U201 (U102 pin 6 to pin 7).
6. 6. Measure for Measure for approximately
U201. U201.
7. 7. If the volta If the voltage at pin 6 of U201 is + ge at pin 6 of U201 is +8V, replace
U102. Before replacing U102. Before replacing U102, make sure
Controller (U462) is good Controller (U46 2) is good. . Go to paragra
to check U462. to check U462.
8. 8. If the voltage If the voltage is other
U201. U201.
e. e. If the voltages If the voltages on bo
approximately +8V, do the following: approximately +8V, do the following:
1. 1. Measure for Measure for approximately
U202. U202.
2. 2. If the voltage is wro If the voltage is wrong, connect pin 6 to p
of U202. of U202.
3. 3. If the If the voltage is voltage is now good,
Before replacing U102, make sure the A/D Before replacing U102, make sure the A/D
Controller (U462) is good Controller (U46 2) is good. . Go to paragra
to check U462. to check U462.
4. 4. If the voltage If the voltage is still wrong, replace U202
f. f. If the If the Ohms Current Ohms Current Source is
replace U203 and then U102. replace U203 and then U102.
7-C-22. 4-WIRE 7-C-22. 4-WIRE OHMS TROUBLES OHMS TROUBLESHOOTING
7-C-23. 7-C-23. The only The only difference b difference between
functions is that the 4-Wire Ohms Function uses the functions is that the 4-Wire Ohms Function uses the
Ohms SENSE Terminals and a different input path in Ohms SENSE Terminals and a different input path in
U102. Make sure the Front/Rea U102. Make sure the Front/Rear Switch is good and that
the wires from the terminals are connected correctly. the wires from the terminals are connected correctly.
Also, make sure the lead resistance of the test used in Also, make sure the lead resistance of the test used in
the 4-Wire Ohms Function is not excessive (<1/30 of full the 4-Wire Ohms Function is not excessive (<1/30 of full
scale reading in the LO INPUT lead and <1/3 of f scale reading in the LO INPUT lead and <1/3 of full scale
in the HI INPUT lead). in the HI INPUT lead). If everyth
U102 U102 may may be be
Go to paragraph
, connect pin 6 to pin 3 in 6 to pin 3
7).
approximately + 8V at + 8V at pin 6 of
8V, replace
U102, make sure the A/D
Go to paragraph 7-C-24 ph 7-C-24
is other than than +8V, re +8V, replace
on both pins th pins of U203 of U203 are
approximately +12V at +12V at pin 6 of
ng, connect pin 6 to pin 3
now good, replace U102. replace U102.
Go to paragraph 7-C-24 ph 7-C-24
is still wrong, replace U202. .
Source is still inoperat still inoperative,
HOOTING
etween the the two two ohms
r Switch is good and that
If everything appears to be good, ing appears to be good,
defective. defective.
replacing U102, make sure the A/D Controller (U462) is replacing U102, make sure the A/D Controller (U462) is
good. good. Go to paragr Go to paragraph 7-C-24 t
7-C-24. 7-C-24. CHECKING THE
7-C-25. 7-C-25. Do the
pin 6 of
Refer to Schematic 3. Refer to Schematic 3.
a. a. Turn the
the A/D
b. b. Move jumpers JM502
"D" position (JM403 pin 1 and 2), as shown in Figure 7- "D" position (JM403 pin 1 and 2), as shown in Figure 7-
C-1. C-1.
place
c. c. Obtain
as follows (shown in Figure 7-C-1) as follows (shown in
are
S S t t a a r r t t : :
S S t t o o p p : :
C C l l o o c c k k : :
pin 6 of
H H o o l l d d : :
S S e e l l f f - - T T e e s s t t : :
G G n n d d : :
in 3
ive,
d. d.
ohms
signatures: signatures:
U462 pin 32: 7ACA U462 pin 32: 7ACA
U462 pin 33: 20FO U462 pin 33: 20FO
U462 pin 34: 666H U462 pin 34: 666H
e. e. If any sig
ull scale
D (Flowchart D) for troubleshooting. D (Flowchart D) for troubleshooting.
Before Before
f. f. If the
defective. defective.
7-C-4 7-C-4
aph 7-C-24 to check U462.
CHECKING THE A/D CONTROLLER A/D CONTROLLER (U462)
Do the following to following to check the check the A/D Contro
Turn the 3478A off 3478A off. .
Move jumpers JM502, JM503, a , JM503, and JM403 to th
Obtain a a Signature Signature Analyzer. Analyzer. Set
Figure 7-C-1): :
T T P P 4 4 0 0 1 1 ( ( J J M M 4 4 0 0 3 3 p p i i n n 6 6 ) ) ( (
T T P P 4 4 0 0 2 2 ( ( J J M M 4 4 0 0 3 3 p p i i n n 5 5 ) ) ( (
T T P P 4 4 0 0 3 3 ( ( J J M M 4 4 0 0 3 3 p p i i n n 4 4 ) ) ( (
G G r r o o u u n n d d P P i i n n ( ( n n e e x x t t t t o o C C 2 2 0 0 3 3 ) )
Figure 7-C-1. JM403 SA Figure 7-C-1. JM403 SA Connection
Turn the Turn the 3478A o 3478A on and n and check the
If any signatures are wr natures are wrong, go to Service Group
If the signatures ar signatures are good, e good, the Input
TM 11-6625-3071-14 TM 11-6625-3071-14
o check U462.
(U462)
A/D Controller. ller.
nd JM403 to the e
Set and and connect connect
) )
) )
) )
O O u u t t
O O u u t t
Connection
check the following following
ong, go to Service Group
the Input Hybrid is Hybrid is