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Page of SY31-0244-2
Revised December 1, 1971
By TNL: SN3 l-0307
4. 1.2.3 Poor Solder Connections and Welds
If a problem appears to be an open diode or an internal
open within the array, a complete resistance check should
be made. Any poor solder connections or welds should be
resoldered.
Also check for an open land pattern
in
the X-return card
(for an X-drive line). If there is an open land pattern, use
a piece of#- 30 wire to repair the break.
See the 5410 Service Aid on resoldering the conneCtions.
4.1.2.4 Shorts Between Drive Lines
Shorts between X- or Y-drive lines usually show up as drop-
ping one or more bits of two addresses. In almost all cases,
analysis of the failing addresses shows that two adjacent X-
or Y-drive lines are the problem. Once the two lines have
been located, make a resistance check of the lines, moving
from one end of the array to the other. Because of the re-
sistance of the windings, less resistance is seen as you get
closer to the short.
In almost all cases, the short is either some foreign material
between two adjacent pins or two pins touching. A visual
check with a strong light may show the short. However, if
foreign material is causing the short, it may not be visible.
Try passing a piece of paper between the pins at the area of
the short.
4.1.2.5 Defective Cores
A defective core position usually shows up as dropping a
single bit in a single address. This type of problem can be
caused by the individual core losing its magnetic properties
because it is cracked, chipped, or broken.
Vary the -30V drive voltage and the strobe setting to see if
the rate of failure changes. If you are unable to obtain a re-
liable operating position, BSM replacement is necessary. See
Sections 4.2 and 4.3 for drive voltage and strobe reoptimiza-
tion.
4-8
4.1.3 Intermittent or Random Failures
If a failure pattern cannot be determined, check the follow-
ing for possible failures causes:
1.
Using an oscilloscope, probe the:
2.
a. XY drive voltage pulses on the XY read and write
current source resistors and compare them to
those in Figures 4-7, 4-8, 4-9, and 4-10.
Note: Probe pins I and 3, which are common. No
pulse will be observed on resistor pin 2, since it is
ground.
b. Z drive voltage pulses on the Z (inhibit) current
limiting resistors and compare them to those
shown in Figure 4-11.
Note: No pulse is observed on resistor pin 2 since
it is the -30V power supply connection. Note also
that the magnitude of the pulses may vary slightly
if the XYZ drive voltage setting is not at -30V.
(XYZ drive voltage supply is a temperature cor-
recting supply.)
c. Control driver (Figure 4-12).
d. Strobe driver (Figure 4-13).
Note: If the strobe driver card is replaced, strobe
jumpers must be put in the new strobe driver card.
Check for improper setting of the -30V, +6V, -4 V,
-14V, and/or +3V. (Use a Weston* 901 meter or
equivalent when adjusting these voltages.)
Note: The + 3V supply should be adjusted with ref-
erence to +6V. This results in a negative reading
(Section 5 .2
.1 ).
3.
Check the voltage connectors to the large circuit
board (SR264 ).
4.
Check if back panel resistor assemblies (not XYZ re-
sistors) are misplugged (SR264 ).
5.
Check for loose interface cables or terminator cards
(SR201, 224, 228, 229).
6.
Check for improper MST-I levels at the interface.
*Trademark of Weston, Inc.
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