HP 437B - MULTIPLE ERROR CODES AND TROUBLESHOOTING SUGGESTIONS (CONT.)

HP 437B
Service Sheet BD1
Table 8-6. Multiple Error Codes and Troubleshooting Suggestions (Cont.)
Troubleshooting Suggestions
66, 65, 70, 68, 69 Verify TTL signals at A3U12 pin 13. If TTL signals are
present, replace A3U12. See the note following in this table.
66, 65, 70, 69, 67 Verify TTL signals at A3U20 pin 7. If TTL signals are
present, replace A3U20. See the note following in this table.
66, 65, 70, 68, 69, 75, 67 Verify TTL signals at A3U6 pin 2. If TTL
signals are present, replace A3U6. See the note following in this table.
Note - A malfunction in any of the following components will cause
the previous three error code combinations: A3U4, A3U6, A3U18,
A3U24, A3U25, and A3U27.
67, 65, 73, 69, 75 Verify TTL signals at A3U6 pin 4. If TTL signals are
present, replace A3U6.
68, 69, 67 Verify TTL signals at A3U20 pin 9. If TTL signals are present,
replace A3U20.
69, 67 Verify TTL signals at A3U18 pin 15. If TTL signals are not
present, replace A3U12. If TTL signals are present, replace A3U18.
70, 67 Verify TTL signals at A3U12 pin 12. If TTL signals are not
present, replace A3U12. If TTL signals are present, replace A3U4.
70, 68 Verify TTL signals at A3U19 pin 4. If TTL signals are not
present, replace A3U19. If TTL signals are present, replace
A3U4 and A3U26.
75, 67 Verify TTL signals at A3U24 pin 39. If TTL signals are present
replace A3U24.
8-28 SERVICE
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