IBM 1620 Manual page 5

CHECK LIST
I. General Information
A. On what operation does the machine fai I?
1. DFT
2. Customer work (Fortran, etc.)
3. Op code of failure
B. What is the frequency of error?
1. Time of day
2. Environment (temperature, etc.)
3. Does customer power fluctuate at certain
time of day? (welder, heavy machinery,
etc .)
II. General Check List
A. Have you checked for loose or bent connectors?
1. 32 pin connectors (x, y, etc.)
2. Edge connec tors.
3. Laminar buss (pins and terminals)
4. TB connectors (power supply, power
sequence, etc.)
B. Have you checked for grounds?
1. DC isolated ground
2. AC isolated ground
3. Ground straps (check contact from the gate
to the frame)
C. Have you checked the Power Suppl ies?
1. Voltage levels
2. Ripple
D. Have you checked Muffin fans?
1. Power supply fans
2. Gate fans
E. Does the machine fai I on margins?
1. Normal margins ± 15%
2 • :::30'10 ma rg ins
*3. Heat
*4. Cold
* Steps 3 and 4 are last ditch efforts and should be used
only after all otherprocedures fail (See Note 1).
III.Core Storage Check List
A. Have you checked the difference voltage using
1/4% accurate meter?
B. What lights are on?
C. What is the pattern of the fai lure?
1. Greater or less than 50; odd or even, etc.
2. Picking or dropping bits
3. What bits are affected?
D. Is the trouble in MBR rather than memory?
E. Memory Temperature 100
0
±
3
0
(Muffin Fan)
F. Have you seoped (using current probe)?
1. x,y drive lines
2.
z
(inhibit) drive lines
2.2
3. Decode Output
4. Current driver outputs
5. All I ines to the inductors
G. Have you scoped the sense lines (us i ng a 535
or equivalent scope and a type IIDII High
Gain Differential Pre-amp plug in unit)?
H. Have you checked the physical wiring of the
indicators?
I. Have you followed scope procedures i,n 1620
CE Reference Manual?
IV. MAR Check List
A. What console lights are on?
1. Op code of failure
2. Previous Op code
3. IIEII or
11111
cycle trigger of failure
4.
Which register failed
5. Fai lure to read, or write
6. Is the trouble in MAR triggers
7. Is the trouble in Inc. Dec. switch
8.
Is the trouble in Multiply Register or
TiC Circuits.
B. Have you scoped (using a current probe)?
1. Read drivers to all registers
2. Sense lines
3. Write drivers to all registers
4.
Bit drivers
Note 1: If errors do not become more frequent with
marginal check part (lor 2), block the fans and let
the gates heat up.
If part 3 does not solve the problem, obtain about
501bs. of dry ice, remove the filters from the gate,
place the dry ice on the floor, then construct a skirt
out of paper and cause all the air to be drawn from
around the dry ice.
Note 2: Observe the function of the IIEII or ' " 1 11 cycle
trigger to determine the register affected. Under some
triggers, more than one register is affected. Be critical
of the timing of the pulses on these lines. If the fail-
ure occurs while writing, it will be detected at the
time it is read out. In order to determine the cause,
scoping must be done at the time of writing. Some
intermediate checks can be performed by use of the
MAR Display Switch, by stopping at different trigger
times and displaying the register in question. Check
to be sure that only the registers called for by a trigger
are being operated on.