IBM 1620 Manual page 41

CORE STORAGE SERVICING PROCEDURE
Because of the size of core storage wires and terminals,
a strong light and magnifying glass is desirable when
broken wires and shorts are suspected.
In diagnosing memory problems, it should be kept in
mind that a short in core storage will cause a split in
Problem
T.
No read or write in any position of memory
2. Missing bits in either all even addresses (or odd)
ina II add resses e ithe r <50 or:>50.
3. Extra bits in either all even addresses (or odd) in
all addresses either<50
0'>50.
4. Dropping all bits in banks of 10 addresses, i.e.,
X02.XX, X 12.XX to X92.XX.
5. Dropping all bits in addresses as patterned below:
(a) 200 addresses
6.
(b) Common digits in either units, tens and ten
K or hundreds and thousands, i.e., OOOXX to
099XX and 100XX to 199XXor OXXOO to
OXX99 and 1XXOO to 1XX99.
With conditions in Step 5 but in banks of 10.
Operation Switch #3
Switch #4
Force all bits Normal Normal
Blank Memory Transferred Transferred
Force Flag
8 1
s Normal Transferred
(88)
Force
7' s (77)
Transferred Normal
4.3
current which would cause the shorted line to carry
less current than is necessary for proper operation.
Therefore, with this type of failure, unpredictable
resul ts can occur:
Possible Cause
Bias winding, current source, or current driver.
Open sense winding or weak presense amplifier.
Shorted inhibit drives.
Open inhibit winding or weak inhibit driver.
Shorted sense amp.
Decode switch or associated wire in matrix switch.
(An open decode switch can cause damage to other
decode switches).
Open X or Y line.
Open inductor.
Switch #5 Switch #6
Transferred Transferred
Normal Normal
Transferred Normal
Normal
Transferred