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c.
Turn off the RP-61 Power Supply.
Remove the 4. 7K resistor and replace the
thermistor leads.
The voltage will change as a function of memory stack temperature (de-
creases O. 5% for a 1 °C rise in temperature) but will be at the proper value for best memory
operation.
The 24v supply can vary typically ±5% without causing memory errors.
Strobe Timing Calibration. -- The timing of the sense amplifier strobe pulse is set for each
unit to give optimum operating margins.
The core stack nameplate shows the time between
the leading edge (1. 5v point) of the RXSWA+ and STRBl- signals.
It
should not be necessary
to adjust the strobe timing.
If a change in timing is required to obtain proper memory oper-
ation, the associated PACs should be checked (e.g., CM-006, CM-032/CM-033, and
PA-335) before a timing change is made.
The CM-003 description in the appendix should be
referred to if a timing change is required.
Corrective Maintenance Procedures
Corrective maintenance procedures consist of electrical and mechanical inspection
and memory system troubleshooting.
Corrective Maintenance Inspection. -- Before beginning troubleshooting procedures, a
thorough inspection of the system should be performed.
Check that the system is not physi-
cally damaged and that no wires have been torn accidentally from the equipment.
Make sure
electrical connectors and PACs fit firmly in their sockets.
Memory System Troubleshooting Procedures
Memory system troubleshooting consists of determining the type of problem, pre-
dicting the µ-PAC at fault, and locating the faulty circuit.
Test procedures to aid in trouble-
shooting are listed below.
CAUTION
Use oscilloscope probes carefully to avoid shorting of connector
terminals resulting in damage to the PAC.
a.
Sometimes, spare PACs may be used. to isolate faulty circuits by interchanging
identical PACs and noting any shift in the faulty bits or addresses.
All memory PACs are
interchangeable except the Timing Distributor PAC, Model CM-003, which has jumper wires
for delay line timing.
b.
Refer to PAC schematic and assembly drawings in the appendix to isolate the
defective components on the printed circuit card.
Replace defective components.
c.
Memory failures are generally of the following types:
1.
Operation failures, which are caused by faulty timing and control circuits.
2.
Partial data word failures caused by a faulty sense amplifier, or data
regeneration circuits.
3-5
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