Electro-Metrics EM-2115, Instruction Manual

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EM-2115APPENDIX 4A TROUBLESHOOTING MICROPROCESSOR BD ASSEMBLY
(EM21154A-1)
APPENDIX 4A
EM-2115
TROUBLESHOOTING MICROPROCESSOR ASSEMBLY A1A3
4A-1.0 Introduction
The information and procedures in Appendix 4A are used for diagnosing problems on the
internal Microprocessor Assembly A1A3 of the EM-2115.
4A-2.0 Failure Diagnosis
The firmware for the Microprocessor Assembly contains built-in troubleshooting aids for
diagnosing problems with any of the internal PIAs' (Peripheral Interface Adapter). This is one of
the more common failures within the microprocesser circuitry.
For certain failures, an error code will flash on the Frequency Display and is associated
with a particular PIA on the Microprocessor Assembly. PIA numbers 1 to 5 are checked each
time a front panel switch is pushed or a remote command is issued. The firmware reads the out-
put of the PIA and compares it to the input of the PIA. If there is a difference, an error message
will flash on the Frequency Display corresponding to the PIA that does not agree.
The error may be caused by any number of things including:
a. A defective PIA,
b. A failure in the circuit being driven by the PIA,
c. A failure in the battery backup on the RAM (Random Access Memory),
d. An out of tolerance condition on the 5 VDC power supply, etc.
4A-3.0 Trouble shooting Techniques
Common sense should prevail when troubleshooting the Microprocessor Assembly since
failures range from the very obvious, to the very subtle. Refer to Table 4A.1 (Common Failures:
Symptoms Vs Causes) for a listing of the most common failure symptoms versus the most likely
causes for that particular problem.
A few points to remember:
a. Always check the +5 VDC supply voltage directly on the Microprocessor Assem-
bly first. The +5 VDC supply must be +5.0 VDC ±0.1 VDC as measured directly
on the Microprocessor Assembly. If the supply is out of tolerance, any number of
failures may become evident. If the supply is out of tolerance, check for bad con-
nections or loose ground connections first.
b. Check and verify that all ICs'and connectors on the Microprocessor Assembly are
fully seated in their sockets.