HP 3478A Technical Manual page 89

3478A 3478A
g. g. The R The RAM c AM can be an be che
from it. from it. One caution when ch One caution when checking the RAM, t
the RAM will be lost and the 3478A will need to be the RAM will be lost and the 3478A will need to be
recalibrated. recalibrated. Do the Do the following: following:
1.To check the RAM, leave the Start and Stop 1.To check the RAM, leave the Start and Stop
inputs of the Signature Analyzer connected as in step c, inputs of the Signature Analyzer connected as in step c,
bu but c t co o nn nnec ect t t the he Cl Cloc ock t k to T o TP5
2. 2. Using Using a fla a flat bla t blade sc de screwdr
CAL ENABLE Switch to the calibration enable position CAL ENABLE Switch to the calibration enable position
(the slot of the switch is in the vertical position, as shown (the slot of the switch is in the vertical position, as shown
on the front panel). on the front panel).
3. 3. Take Take the the follow following
U512 pin 11: C577 U512 pin 13: 4296 U512 pin 15: U512 pin 11: C577 U512 pin 13: 4296 U512 pin 15:
8U25 8U25
4. 4. If th If the sig e signat nature ures are w
defective. defective. Before re Before replacing t placing the RAM
RAM's R/W line RAM's R/W line reads a reads a signature
signature is wrong, signature is wrong, replace U515. replace U515. If the
good, replace U512. good, replace U512.
5. 5. If If the the signa signature tures are
cause the cause the failure. failure. Go to Go to Flowchart
D-I 1) for further troubleshooting. D-I 1) for further troubleshooting.
7-D-25. Voltmeter 7-D-25. Voltmeter Complete Complete
7-D-26. The Voltmeter Co 7-D-26. The Voltmeter Complete pulse is
put after put after an an input input measurement measurement is is completed.
troubleshoot the operation, with a logic probe, check and troubleshoot the operation, with a logic probe, check and
make sure pin 25 of US01 is toggling. make sure pin 25 of US01 is toggling. If the probe doe
not show not show toggling, US01 toggling, US01 is most likely
probe shows toggling, make sure R538 is not open, and probe shows toggling, make sure R538 is not open, and
CR504 and C CR504 and CR505 are not R505 are not shorted.
diodes are good, replace U508. diodes are good, replace U508.
7-D-27. 7-D-27. Address Address Switch Switch Failure
7-D-28. 7-D-28. An address swit An address switch failure can be caused by
switch itself or US10. switch itself or U S10. The address switch The address switch can easily b
checked using a logic probe. . With all switches of the ad- checked using a logic probe
dress switch on (up), pins 9, 10, 11, 12, 13, 14, 15, and dress switch on (up), pins 9, 10, 11, 12, 13, 14, 15, and
16 of the 16 of the switch are switch are low. low. With all switches off
the pins are high. If the switch is g the pins are high. If the switch is good, replace US10.
7-D-29. 7-D-29. External External Trigger Trigger
7-D-30. 7-D-30. An external An external trigger failure trigger failure can be cause
defective U514 defective U514 or HP-IB Chip. or HP-IB Chip. Do the following:
a. a. Set Set the 3 the 3478 478A to t A to the Si
b. b. Usi Using a ng a log logic pr ic probe
high. If the pin high. If the pin 1s low, do 1s low, do the following:
checked b cked by re y readi ading da ng data ba
ecking the RAM, the data in
P5 ( ( ). ).
rewdriver, iver, set t set the fr he front p
ing signa signature tures. s. U512 U512 pin pin 9: 9: H709
s are wron rong, th g, the RAM ma e RAM may be
he RAM, make , make sure t
signature of 4296 of 4296. .
If the signature is signature is
s are good good, ot , other her circu circuitry
Flowchart A (see A (see paragraph paragraph 7- 7-
mplete pulse is normally out normally out- -
completed.
If the probe does s
is most likely defective. defective. If the
shorted. If the resistor If the resistor and
Failure
ch failure can be caused by the
can easily be e
With all switches of the ad-
With all switches off (down),
ood, replace US10.
can be caused by
Do the following:
he Singl ngle Tr e Trigg igger m er mode ode. .
obe, mak , make su e sure pi re pin 5 of U n 5 of U514
the following:
ta back ck
he data in
c. c. If p
pulse (i.e., toggle) pin 5. pulse (i.e., toggle) pin 5.
d. d. Usi
ont panel anel
U514. U514.
e. e. If p
while checking the pin with a logic probe, apply a trigger while checking the pin with a logic probe, apply a trigger
pulse to the 3478A's EX TRIG connector (i.e., short the pulse to the 3478A's EX TRIG connector (i.e., short the
H709
input of the connecto input of
triggered, pin 9 of U514 should toggle high and then l triggered, pin 9 of U514 should toggle high and then low.
f. f.
y be
toggle, USO1 may be defective. toggle, USO1 may be defective.
sure the he
If the If the
7-D-31. 7-D-31. FLOATING COMMON
7-D-32. Floating Common F 7-D-32.
A/D Converter an A/D Conv
itry may may
paragraphs have the failures and troubleshooting paragraphs have the failures and troubleshooting
information. information.
7-D-33. 7-D-33. Pre-Troubleshooting
7-D-34. 7-D-34. Before
Logic Circuitry and A/D Logic Circuitry and A/D Converter, perform the following:
To To
a. a. Che
Supplies. Make sure they Supplies.
If the
level, and are not oscillating. level, and
follows: follows:
and
the
b. b. Che
are at the correct level a are at th
can be checked at U405 pin 6, the -10V supply at U404 can be checked at U405 pin 6, the -10V supply at U404
(down),
pin 6, and the buffered + 10V supply at JM201. pin 6, and the buffered + 10V supply at JM201.
c. c. Mak
is good, is good, as shown
d by a a
missing or incorrect, make sure the CPU's clock (at pin missing or incorrect, make sure the CPU's clock (at pin 2 2
and 3 and 3 of U462) is
Y460, if the Y460,
U462. U462.
7-D-35. A/D Converter 7-D-35.
514 is is
7-D-36. 7-D-36.
Overload, Constant Zero, Floating, or Noisy Overload, Constant Zero, Floating, or Noisy Readings.
7-D-7 7-D-7
1.Check for a low at pin 4 of U514. 1.Check for a low at pin 4 of U514.
2.If pin 4 of U514 is low, replace U514. 2.If pin 4 of U514 is low, replace U514.
3.If pin 4 of U514 is high, replace U503. 3.If pin 4 of U514 is high, replace U503.
If pin 5 o in 5 of U51 f U514 is hi 4 is high, u
Using a lo ng a logic p gic prob robe, c e, chec
If pin 9 in 9 is l is low ow, re , repla place U ce US14
the connector to g r to ground). round). When the 3478A
If If pin pin 9 d 9 does oes not not tog toggle gle, r , repl
FLOATING COMMON LOGIC FAILURES
Floating Common Failures can be failures ailures can be failures in the
erter and the d the A/D Cont A/D Controller.
Pre-Troubleshooting Information
Before troubleshooting troubleshooting the
Converter, perform the following:
Check th ck the 34 e 3478A 78A's F 's Floa
Make sure they are stable, ar are stable, are at the correct
are not oscillating. The power supplies a The power supplies are as
P P o o w w e e r r C C h h e e c c k k e e d d
S S u u p p p p l l y y a a t t
+ 5V V + 5 J J M M 7 7 0 0 1 1
- - 1 1 5 5 V V J J M M 7 7 0 0 2 2
+ + 1 1 5 5 V V J J M M 7 7 0 0 3 3
Check an ck and make d make sur sure th
e correct level and are quiet. nd are quiet. The + 10V supply
Make su e sure t re the A he ALE l LE line ine at TP
as shown in Figure in Figure 7-D-S.
of U462) is at 10.98M at 10.98MHz.
if the signal is missing. signal is missing. If still missing,
A/D Converter Failure and Failure and Troubleshooting
An A/D Conve An A/ D Converter fa rter failure can
TM 11-6625-3071-14 TM 11-6625-3071-14
gh, usin sing a log g a logic pu ic pulse lser, r,
heck for a h k for a high a igh at pin 9 o t pin 9 of f
S14. . If t If the he pin pin 1s h 1s high igh, ,
When the 3478A is is
ow.
eplace ace U51 U514. 4. If If it it doe does s
LOGIC FAILURES
in the
roller. The following The following
Information
the Floating Floating Common Common
loatin ting Com g Common P mon Powe ower r
e at the correct
re as
V V o o l l t t a a g g e e
l l e e v v e e l l
+ + 4 4 . . 9 9 V V t t o o + + 5 5 . . 1 1 V V
- - 1 1 4 4 . . 4 4 V V t t o o - - 1 1 5 5 . . 6 6 V V
+ + 1 1 4 4 . . 4 4 V V t t o o - - 1 1 5 5 . . 6 6 V V
e the Ref e Refere erence S nce Supp upplie lies s
The + 10V supply
at TP403 ( 403 (U46 U462 pin 2 pin 11)
7-D-S. If the signal is If the signal is
Hz. Try replacing Try replacing crystal crystal
If still missing, replace replace
Troubleshooting
ilure can show show up as up as
Readings.
11)