EAI 580 Computing System — General Maintenance Instructions (Chapter 2)
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CHAPTER 2
GENERAL MAINTENANCE INSTRUCTIONS
2.1 GENERAL INFORMATION
This chapter provides the maintenance technician with general information concerning the 580
Computing System. The Computing Components manual of this series (EAI Publication Number
00 800. 2057-0) provides a specific maintenance guide for each individual tray,
The technician is referred to the following: (a) Reference Handbook for patching procedures
of the various computational components (EAI Publication Number 00 800, 2055-0); and Ap-
plications Reference Library Bulletins available through the EAI Advertising Department,
West Long Branch, New Jersey.
2.2 PREVENTIVE MAINTENANCE
The primary goal of preventive maintenance is to minimize downtime. This is accomplished
by a systematic check of the equipment to detect any decline in performance. Detailed and
carefully maintained records and malfunction reports should be kept. These records (if care-
fully analyzed) will provide information to evaluate a given maintenance program, This per-
mits the maintenance technician to establish an efficient program for his particular installa-
tion.
The preventive maintenance routines are divided into two groups. These groups are frequent
(daily to weekly) checks, and infrequent (semi-annual) checks.
2.2.1 Daily to Weekly Checks
GENERAL MAINTENANCE INSTRUCTIONS
Perk i. unloading amplifier balance and unloadi
teient warm-up (1/2 hour).
ng adjustment after suf-
Check RDAC amplifier balance,
ee SaHpmeat should be checked for ink and paper supply as well as for |
general operating conditions and calibration.
. &
8. The readout functio
t functions should be checked for operation.
- certa at all equipment necessar eduled operation is available and
in operating condition.
GENERAL MAINTENANCE INSTRUCTIONS
EAI maintains a highly trained and skilled Service Engineering staff that is available to a cus-
tomer on two terms: either resident or temporary basis. The Suggested preventive mainten-
ance routines are based on the experience of this staff in both EAI Computation Centers and
Customer installations throughout the world.
2.3 SERVICE TECHNIQUES
The following Suggestions and techniques are given to aid maintenance personnel who are not yet
familiar with the servicing of transistorized equipment.
2.3.1 Etched-Circuit Board Soldering
The techniques and precautions employed while soldering any electronic equipment apply to |
etched-circuit boards; however, several additional factors should also be considered.
Wire leads or components fastened to the board by their leads may be replaced in the following
manner:
1. If a component (IC can, transistor, ete.) is to be replaced, remove it with a pair
of "flush cutters" by clipping the leads as high, and as close to the "can" as pos-
; sible (Figure 2.1), Remaining now are only the wire leads,
CLEAN
. <— BOARD
cea A, pence BY =
SOLDER PULLING DOWNY
Figure 2.1. Removat of Flat Pack
tions, and
4. Bend the leads on the new components or jumper to fit the board connections,
insert the component without cutting the leads.
5. With the component held in place, touch the iron to the lead allowing solder to a)
down the lead and form a fillet. As soon as fillet is formed, remove the iron. ; i
not necessary to completely fill the hole with solder as some components (transistors,
diodes, etc.) are easily damaged by excessive heat.
ible
6. When all leads have been soldered, cut the lead off as close to the board 4 ee
n a
(flush cutters). Carefully scrape off excess flux and solder from the board wi
of the components is much easier if special soldering iron tips such as the Ungar Elec-
iber 856 (5/8 inch diameter cup) and Number 858 (bar) are used. These tips are
onent removal only, and permit all leads to be freed together.
of bus wire over it. Again, extreme care should be taken not to over-
it to separate from the board,
can be damaged by excessive heat. If it be-
sistor, the transistor should be removed
treme care should be taken to prevent
and work as quickly as possible,
ved only when there is
or diodes, a heat sink
s<ENERAL MAINTENANCE INSTRUCTIONS
a a a
CHAPTER 2 GENERAL MAINTENANCE INSTRUCTIONS
common method of accomplishing this is by using a mica, anodized aluminum, or fiberglass
washer with silicon grease. The washer provides electrical insulation and the Silicon grease
increases the heat conduction. When replacing the power transistor, use only a single washer
and coat both sides with silicon grease; Dow Corning Number 340 Compound, EAI 00 942, 0025-0
(or equivalent). As a final precaution before applying power to the unit, check the resistance
between the body of the transistor and the heat sink to ensure that no short or high resistance
leakage patch exists between these points.
Diodes, electrolytic capacitors, and the transistors themselves used in transistor circuits are
frequently damaged by voltage overlaod. Transistors should never be removed or inserted with
power applied, and special care must be taken in the selection and use of test equipment. Sig-
nal generators commonly used in servicing vacuum tube circuits are often capable of producing
enough output to overload and permanently damage the diodes, electrolytic capacitors, and
transistors of the type used in transistor circuits. Always start with the minimum output sig-
nal and slowly increase it to the desired level,
The meter used for continuity and resistance checks must be carefully chosen. Some ohmmeters
use batteries with a higher voltage rating than the transistors and capacitors being checked, and
can destroy them. A meter witha 1-1/2 volt battery is recommended. In order to prevent
damage to the small electrolytic capacitors it is essential to determine the polarity of the ohm-
meter leads. This may be accomplished with another meter set to a low de scale,
2.3.3 Transistor Troubleshooting
As with any other type of electronic circuit, the first step in troubleshooting transistor circuits
is a visual inspection for charred, discolored, or leaky components; broken, shorted, or
loose connections; heavily tarnished or broken connectors; and physical damage to the board
itself. The next step is to replace any relays, ovens, or choppers, which are socket mounted
on the board, with units known to be good. This is done not only because it is fairly easy, but
also because each contains mechanical moving parts which may fail due to normal wear. If the -
trouble is not located by either of these steps, the board may be dynamically tested by applying
all supply voltages and a signal input and then checking voltages and signals on the board until
the trouble is isolated. If dynamic testing is impossible due to the lack of. oo
availability of "down time” on the equipment in which it is used, the
GENERAL MAINTENANCE INSTRUCTIONS
Others are effectively isolated by capacitors in series with them. When it becomes
po unsolder and lift one end of a component from the board to isolate it for resistance
resistors Should be chosen whenever possible. Resistors are least likely to be damaged
Tn many cases, by carefully selecting the correct lead to disconnect, several compon-
ted at one time.
. ssary to risk overheating a transistor by unsoldering it to make resistance
+ For example, lifting one end of the collector load resistor and one end of the emitter
© would effectively isolate the transistor in a normal transistor amplifier stage.
is isolated, it may be checked using the following procedures:
1, Set the ohmmeter to a high range and connect it between the base and the collector
_ leads; reverse the leads and note which connection caused the higher reader. This
is the reverse-bias direction.
the ohmmeter to reverse-bias the transistor and note the reading. Short
1¢ emitter. The reading should decrease. Remove the short.
the base to the emitter and note the reading. Reconnect the short,
GENERAL MAINTENANCE INSTRUCTIONS
If the programmer reports a malfunction during a problem run, the technician should request
& copy of the programmer's computer diagram, amplifier and attenuator assignment sheets, etc.
The technician should be familiar with both Analog and Digital programming symbols and var-
ious programming notations in order to obtain maximum information from the data,
Because the Console is a completely self-contained Computer, disconnection of the peripheral
Sear will locate the faults in either the console or the
Component is located, maintenance information conc
handbook, and/or chapter within the 580 Maintenance
associated manuals at the front of this manual,
peripheral equipment. Once the major
erning that unit may be found in the respective
€ manuals. Refer to the index and list of
The DVM, display unit, and monitoring oscilloscope are also very useful in troubleshooting,
When a particular tray is suspect, interchange it with an identical unused tray and, if the trouble
a clears, the fault is isolated to the replaced tray. If the tro
uble remains, the patching is prob-
ably in error, If an unused tray is not available, switch position with an identical unit that
is in use and check to see if the malfunction follows the tray.
= -
Another method is to remove the patching from the Suspected unit and patch in its place, an 1
hed identical unit. If the trouble is cleared, repatch the original unit back into the problem to as-
_—_ ? certain that some unnoticed patching error was not rectified in the change.
7 ~ 2.5 MAINTENANCE EQUIPMENT
—- a
7 In the 580 Computing System, most components are mounted on plu
g-in cards and/or trays. This
allows rapid replacement of a defective unit with a spare unit. The interruption to con putation.
is brief; actual repair of the defective unit can then be made at the convenience of the technician.
With this concept, it is necessary to maintain a supply of spares. The
ular rotational schedule, allows regular computer comp rents toga th:
tenance with little or no computer down-time, 4 m