Electro-Metrics EM-2115, Instruction Manual

Page: 120 / 278

EM-2115APPENDIX 4A TROUBLESHOOTING MICROPROCESSOR BD ASSEMBLY
(EM21154A-4)
COMMON FAILURES: SYMPTOMS VS CAUSES
SYMPTOM-3
Front Panel Frequency Display has an error message indicated when:
1) Front panel switch is pushed.
2) Remote command given.
The error message format will be similar to the following example:
E40
Where: 4 means PIA #4 output does not agree with input.
POSSIBLE CAUSE-3
a. Failed PIA. (In example given: PIA #4 or U24.)
b. Output of PIA is being loaded or affected by the circuit which the PIA is control-
ling.
NOTE-3:
Refer to Table 4A.2, Address MAP, to translate PIA number to Reference
Designation number. Refer to Table 4A.3, PIA Table Listings, to obtain
what functions are controlled by a given PIA.
SYMPTOM-4
Total Failure, all functions in unit.
POSSIBLE CAUSE-4
a. A1A3-U16 has failed.
b. Crystal A1A3-Y1 has failed.
NOTE-4:
If the front panel switches or displays are partially working, then the mi-
croprocessor IC A1A3-U16 itself is probably okay.