HP 3484A Operating And Service Manual page 57

PRELIMINARY CHECK
Check power supply voltages.
NOTES
I . Use INPUT LOW (black} terminal as ground
connection unless otherwise stated .
2. After repair of Amplifier Assembly, perform
Adjustment Procedures, Paragraph 5-13.
34 8 4 A-C - 3039 4
Model 3484A
PASSES
Q
I. Set 3484A FUNCTION to VDC, RANGE to
JO V, SAMPLE RATE fully clockwise, FILTER
OUT. Remove Amplifier Assembly A3 (or AS}
from 3480A/B. Connect 3484A E;n(J2 pin 7) to
Sense (J2 pin 9). Connect de voltmeter between
Em
and INPUT LOW terminal. Connect de
standard to 3484A INPUT. Set standard output
to 15.990 V. (If limiting occurs on only one
polarity , set de standard output to this polarity.)
DC voltmeter reading should be the same as de
standard output.
FAILS
2. If de voltmeter reading is the same as INPUT
voltage, trouble is in 3480A/B. Refer to 3480A/B
Operating and Service Manual.
3. Replace 3480A/B Amplifier Assembly and dis·
connect short from
Em
to Sense. Disconnect de
voltmeter. Disconnect one end of either A2CRl4
or I 5 . Display should be approximately
15.990
v.
Section V
4. If display is correct, and limiting occurred with
positive input voltage, A2CRl4 is probably
shorted.
5. If display is correct , and limiting occurred with
negative input voltage, A2CRI 5 is probably
shorted.
6. If limiting is still present with positive input
voltage reconnect A2CRl4 or 15. Check A2CR20
and A2Ql9.
7. If limiting is still present with negative input
voltage, reconnect A2CR14 or 15. Check
A2CR26 and A2Q20.
Figure 5-13. Limited DC Display Troubleshooting Tree.
5-19