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Two singleshots (135 ns and 450 ns) in the clock
section of the M9/M9A should be checked and adjusted.
The 450-ns singleshot (AlH6D09) prevents any read
reset pulse during the first part of a read cycle.
If
the 450-ns singleshot does not fire, check the +18-
volt power supply.
When scoping main storage, especially the clock
section, the best place to sync the scope is write
control at AlH6J07. All timing is with respect to
plus store select as it appears at AlH6G05.
X read/write driver timing (AlH6B07) and Y
read/write driver timing (AlH6J05) should be a 2. 5-
to 3. 0-volt signal. A pulse of less than 2. 5V de-
creases driver current and causes random failures.
The read-write latch is a 6. 0-volt pulse.
If
zeros
cannot be read, check to see that strobes A and B
at AlJ6G12 and AlJ6J04 are present.
I
Delay Line Driver
In checking the delay line card (4906), be sure that
the input to the delay line driver 02A-AlC6Dll is a
positive pulse (Figure 58). The output of the delay
line driver (02A-AlC6Jll) should be the same as
the input.
If
the output of the delay line driver (02A-AlC6Jll)
has ghost pulses between the normal pulses, the delay
line is open and the card should be changed.
If
there
is no pulse at 02A-AlC6Jll on delay line card
(4906), the delay line driver may
be
bad.
If
chang-
ing the card does not correct the pulse, there is
probably something shorting out the delay line (for
example, a cold flow on one of the yellow timing
wires). Check the yellow timing wires associated
with the delay line card to see
if
any of them are
pulled tight around a pin and shorting out. The tim-
ing chart on ALD Page AAOOl should be used if any
storage timings are changed.
.J!
" ;
T
...... .-1
-
. .
:
.J
"
v
FIGURE 58. INPUT TO DELAY LINE DRIVER
84
(3/71)
.Model SO FEMM
I
Layout of M9/M9A Plane
Figure 59 is a block diagram of the M9/M9A read-
write drive system. Layout of the planes is in
Figure 60.
X drive lines in Figure 60 on pins 6 through 69
go through all 18 planes to the D2 board on the back
of the array, jumper down, and come back through
all 18 planes on pins 228 through 291. X drive lines
on pins 80 through 143 go through the array to the D2
board, jumper down, and come back through the
array on pins 154 through 217.
Use a current probe when checking the drive
circuits. Currents should be checked on the gray
wires to card locations BlM2 and BlG6 on the BSM.
The X current will be on the -gray wires to pins G03
and J04. The Y current will be on the gray wires to
pins Dl2 and Bl2.
+60V
+60V
Read
Dvr
Gate
Decode
Read
Terminator
Write
Dvr
Cl Board
FIGURE 59. M9/M9A DRIVE SYSTEM
I
X Drive Current
B
Read Gate
Transistor
Write Diode
Network
Read Diode
Network
Write Gate
An example of good X current is shown in Figure 61.
The read pulse is longer than the write.
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