External Trigger Inoperative; Voltmeter Complete Inoperative; Hp-Ib Address Selection Inoperative - HP 3456A Operating And Service Manual

Service
panded waveform.) Ir the waveform is not present,
replace U21.
A
. 2V
5 ,.sec.
2 ,.sec.
Figure 8·A·12. Receiver Date.
d. Measure for the waveform shown in Figure 8-A-13
at pin 14 of U21. If the waveform is not present, replace
U21. If the waveform is present, make sure the same
waveform is at pin 8 of U22. I f the waveform is not at
pin 8, try U2 and/or U6.
. 2 V
5 ,.sec.
Figure 8·A·13. Figure Receive Clock.
e. Use a logic probe and make sure pin 9 of U22 tog­
gJes. I f pin 9 toggles, continue with the next step. If pin
9 does nOl toggle. make sure pin 1 3 of U I 3 toggles. If
pin J 3 does not toggle. replace U13. If pin 14 toggles,
replace U 1 1 .
f. Make sure pin 1 of U20 toggles. If not, replace U6.
g. Connect channel A of a dual trace oscilloscope to
pin 3 of U22 and channel B to pin I of U20 (use the
scope set-up information in Figure 8-A-14). Make sure
the measured waveforms are as shown in Figure 8-A-14.
Also make sure pin 4, 5, 6, and 1 3 are the same as pin 3.
If any waveforms are bad, replace U22.
8-A-20
Pos. Trig.
Pos. Trig.
Pos. Trig.
h. Using the same set·up as in Step g (previous step),
connect channel A of the oscilloscope to pin 10 of U22.
Make sure the measured waveforms are as shown in
Figure 8-A- 1 5 . Also make sure pin 1 I and 12 are the
same as pin 10. If any waveforms are bad, replace U22 .
. 2 ,.sec.
Figure 8·A·14. High level Data.
If all of the waveforms in Step g and h are good,
1.
replace U20.
.2V
.2 ,.sec. Nag. Trig. use Channel B
Figure 8·A·15. Low Level Data .
B-A-47. MISCELLANEOUS FAILURES.
8·A·48. External Trigger Inoperative.
8-A-49. Make sure pin 5 of A3U5 changes from low to
high to low, when the 3456A is externally triggered. If it
does not, make sure diodes CR3 and CR4. resistors R2
and R3, and U4 are good. I f still bad, replace A4U 19. If
pin 5 of A3U5 does change, replace A3U 16.
B·A·50. Voltmeter Complete Inoperative.
8-A-5 1 . Make sure diodes A3CRI and CR2 are not
shorted. Try A4U19.
B·A·52. Hp·IB Address Selection Inoperative.
8-A-53. Make sure the 3456A HP-IB is otherwise work­
ing correctly. If not, go
troubleshooting. I f it is good, try A3U16.
Model 3456A
Pos. Trig. use Channel A
10
Paragraph 8-A-25 for
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