Photodiode And Amplifier Troubleshooting; Table 8-4. Signature Table - HP 5501B Operating And Service Manual

Pin U1
1 41A5
2 0000
3 8816
4 F9C3
5 UA4P
6 CCPC
7 0000
8 27HH
9 6678
10 OP7C
11 4UHP
12 7U30
13 3P9S
14 41A5
15 NC
16 NC
NC = A3U1-3, A3U5-6, and A3U19 are 14-pin package Configuration.

8-140. Photodiode and Amplifier Troubleshooting

8-141. This procedure assumes that the power supplies are functioning properly. Use a dedicated
digital voltmeter, not the signature analyzer voltmeter function.
a. Bypass high-voltage interlock by setting A1S2 to TEST. Set HTR OK jumper to LO,
PHOTO DIODE jumper to TEST, LIQ CRYS jumper to PASS. Is voltage at TP16 more
negative than -4V? If no, go to step e. If yes, go to step b.
b. Set LIQ CRYS jumper to ACT. Is voltage at TP16 more positive than -1V? If no, go to step
e. If yes, go to step d.
c. Verify U11 (Pin 13) is 0 V ±10 m V. If not, replace U11. Verify voltage atTP16 is 6/11 of
that at U11 D pin 14 and voltage at junction of R20 - R22 is 1/11 of that at U11D (Pin 14).
If not, check A3R6, R17, R20, R22, and R24. Also U12A or U12D may be incorrectly
loading this node.
d. Amplifier is OK. Check photodiode. Verify laser is on. Set PHOTO DIODE jumper to NRM.
Measure TP16 voltage. If it is >=+0.5V then photodiode A4CR1 is good. If it is
approximately -6V then either the photodiode is shorted or U11 is bad. If it is -0.5V to
+0.5V go to step e.
e. Remove PHOTO DIODE jumper and check for diode action between the left hand pin of
the jumper and ground. If no diode action is observed, replace A4CR1. Otherwise, not
enough light is reaching the photodiode. Remove the A6 Sampler Assembly and inspect
the liquid crystal, beam splitters and A4CR1 for dirt, scratches, etc. If OK, see Liquid
Crystal Troubleshooting.

Table 8-4. Signature Table

U2 U3 U4
4UHP CCPC 6678
7U30 41A5 0000
41A5 FP96 8A5F
4A39 41A5 0000
41A5 FP96 2OH3
4A39 8U33 FP96
0000 0000 UA4P
7130 3P9S 0000
8U33 7U30 6678
6678 41A5 AOHO
538U 20H3 88F5
F9C3 FP96 0000
41A5 CCPC 538U
41A5 41A5 0000
NC NC 4UHP
NC NC 41A5
US U6
4CCA 41A5 CCPC
FP96 0000 41A5
P861 FO9F 27HH
4UHP CU8C 0000
P861 267H 41A5
4H86 9CHA UA4P
0000 0000 0000
41A5 4UHP 34FP
41A5 4CCA 7C10
41A5 4A39 4UHP
A5P7 FF57 41A5
P861 0000 34FP
OP7C 9CHA 4UHP
41A5 41A5 41A5
NC NC NC
NC NC NC
HP5501B
Service
U8 U9 U19
4CCA F9C3
4H86 8816
A5P7 41A5
4UHP 0000
7130 4A39
6678 3721
7C10 0000
0000 0000
UA4P 41A5
34FP 3721
7U30 7U30
FP96 0000
41A5 CCPC
0000 41A5
XXXX NC
41A5 NC
8-41