HP 437B Service Manual

HP 437B
Service Sheet BDI
Table 8-5. Single Error Codes and Troubleshooting Suggestions
Troubleshooting Suggestions
61 only Stack RAM failure (A3U9).
Check for TTL signals at A3U9 pins 20, 22, 27.
If TTL signals are present, replace A3U9.
62 only ROM checksum failure (A3U8).
Replace A3U8.
64 only RAM failure (A3U9).
Replace A3U9.
65 only Analog I/O PIA Failure (A3U24).
Replace A3U24.
66 only Keyboard and Display PIA Failure (A3U25).
Verify TTL signals at A3U22 pins 21 and 22. If signals are
67 only
present, replace A3U25.
If a TTL signal is not present at A3U9 pin 20, connect a logic probe
to A3U12 pin 10. Set the Power Meter’s LINE switch to STBY, then ON.
A high-low-high transition should be detected at A3U12 pin 10. If not,
replace A3U12.
Analog-to-Digital converter failure.
Verify TTL signals at the following locations
on Service Sheet A3b: A3U12 pin 11, 13. A3U14 pins 7, 10, 11.
A3U18 pins 13, 26. A3U24 pins 5 - 8, 40. If the TTL signals are
present, troubleshoot circuit block Q on Service Sheet Adc
and circuit blocks L, M, and N on Service Sheet A4b.
HP-IB failure (A3U4).
Verify a TTL signal at A3U12 pin 12. If present, replace A3U4.
Timer failure (A3U18).
Verify TTL signals at A3U16 pin 3, A3U22 pins 16 , and
A3U18 pin 3. If present, replace A3U18 or A3U21.
Verify TTL signals at A3U18 pin 3, then check for a TTL low at
A3U21B pin 9. If A3U21B pin 9 is not low, replace A3U21.
If a TTL signal is present at A3U18 pin 3 and A3U21B pin 9 is
at TTL low, check for TTL signals at A3U22 pin 16. If TTL signals are
not present at A3U22 pin 16, replace A3U22.
SERVICE 8-25

HP 437B Specifications

General

Brand	HP
Model	437B
Category	Measuring Instruments
Language	English