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Power Faults
See the section, Power System Service Checks, in
this manual.
Loading Faults
See the section on FLTs in this manual. Remember
that none of the central processing unit and very little
of the channel circuitry is used to load FLTs.
·
Programming Faults and Error Stops
Programming faults and error stop approaches to
troubleshooting are shown. Note that:
1. The machine status is logged out before begin-
ning a troubleshooting sequence.
2. FLT's are run before functional tests.
OTHER MAINTENANCE DOCUMENTATION
Error Check Analysis Diagrams
Error check analysis diagrams (ECAD' s) are com-
puter-drawn, engineering controlled, schematic
representations of the error register and the cir-
cuitry behind each possible error indication.
AL6
1 ---------
~
TR20
H
3
5
Position 4 - - - -
6
ECAD's are in Volume 1 Reference of Systems
Diagrams. To use ECAD's, turn to page UCA101
and find your particular error in the error register
block diagram. The numbers to the left of the error
register lead you to an ECAD specifically tailored
for that error. Further to the left is the ALD page
number of the parity checker for that error.
Each ECAD contains a block diagram simplified
to show the basic logic of the error checking circuit
and a list of ROS functions that pertain
to
the circuit.
In
addition, basic timings, scope points, pertinent
notes, and the complete logic for at least one bit
position of the error circuit are shown wherever
necessary.
Figure 2 shows how to read an ECAD block.
SERVICE AIDS
This section is for Customer Engineering Memoran-
dums (CEM's) and other aids helpful in servicing the
Model 50. CEM's are generated and distributed by
Field Engineering Technical Operations as the need
for them arises.
ALD Page Key
Figure 3 is a key to the Model 50 ALD pages showing
the basic content of each section of the ALD's.
1.
ROS Functions: Specifies the goting into the register. Enough of the control field specifications are reproduced to permit interpretation
of the function. In this example, AL6 would
be
shown
as
IAR
H(B-31), and TR 20 would be shown as Latch
H(0-31). Thus the two
sources of input to the H register are the latch and IAR. By examining the ROS word in control during the error cycle, the source of the
data in the H register can be pinpai nted.
2. Name of Register: Self explanatory.
3. ALO Pages: Self explanatory.
4. Scoping Paint: Refers to an entry in a testpaint table, from which scoping information can
be
obtained.
5.
Logout Location:
Refers ta the storage word(s) into which the register is logged on an error log out. This is a decimal
word address.
6. Indication: Specifies where in the switchable indicators the register is displayed.
FIGURE 2. ECAD BLOCK KEY
12
(3/71)
Model SO FEMM
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