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3-6
3.
Address failures caused by faulty selection circuits.
d.
Memory failures may be localized by the following procedure:
1.
Load the test pattern into the memory.
2.
Initiate a read operation at each address sequentially and check each read-
out for the following failures:
(a)
Operation failures:
No apparent response to commands applied to the
memory, or faulty operation at all addresses (Table 3-2)
(b) Partial data word failures:
Failures of one bit or series of two or
more bits at all addresses (Table 3-2)
(c)
Address failures:
Faulty memory operation at particular addresses
only (Table 3-2)
3.
These procedures may sometimes be accelerated by the continuous
memory access mode.
The computer can be placed in the continuous
memory access mode by the insertion of a jumper wire between
AlB3304 and AlB3333.
The jumper enables the continuous memory
access mode.
With the machine in the memory access mode, when the
start button is pressed, memory will be accessed at a 1 me rate.
Table 3-2.
Failure Modes and Probable Causes
Symptoms
No apparent response to
commands
Unable to read from any
address
Failure of one bit (ZERO or
ONE) at all addresses
Failure of one bit at certain
combinations of binary
address digits
Failure of one bit at one
address
Failure of four bits at
particular addresses
Probable Fault
1.
D. C. Voltage
2.
Loose or damaged cable PACs
3.
CM-003 PAC failure
4.
BANKX- passive
5.
Timing and control fault:
MCSET+, MEMCI+, MBSYL- and
RDATA- signals
1.
Read and Write CM-003 PACs
interchanged
2.
24 V supply
3.
STRBl+ signal
4.
RRCXX+ command
5.
BANKX- signal
1. Sense Amplifier PAC
2. Y -Switch or Sink PAC
3 . T G - 3 3 5 circuit
4. Sense winding
5. Data input missing
1. Sense Amplifier PAC
2. Y - Switch or Sink PAC
3. Y -Drive line
4. Y -Selection diode
1. Marginal voltages
2. Marginal Sense Amplifier PAC
1. Y -Switch PAC
2. Backplane resistors
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