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TAPE UNIT TESTER
A field tester (Figure 17) is used to perform off-line
maintenance on 2420 tape units. (Tester must have
Engineering<Change # 731211 installed for 2420.:.7 opera-
tion.) External power cable (part 460663) is required to
power the tape· unit and tester. When operating with the
field tester, the 2420 tape unit can perform read, write,
rewind, .and rewind-unload operations.
To Use !he field tester, turn tape power off, connect
the tester cable to tape unit signal connector A, and
insert a line terminator (part 5417910) in signal con-
nector B. To perform an operation, turn tape power on,
mount and load a work tape, put the tape unit in 'ready'
status by depressing the tape unit start pushbutton, and
set the field tester controls for the desired operation.
Figure 18 shows the tester control settings for given
operations.
Tester Switches and Controls
Rewind-Unload
This spring-loaded switch sends a rewind-unload signal to
the tape unit to rewind and unload tape if the start/ stop
switch is in the stop position.
Rewind
This spring-loaded switch sends a rewind signal to the
tape unit to rewind tape to load point if the auto-cycle
switch is off.
Auto-Cycle
This two-position switch is set to the auto cycle position
to cause a rewind signal to be gated to the tape unit
when the end-of-tape reflective marker is sensed; in this
position, the rewind switch is disabled. In the off posi-
tion, it enables the rewind switch.
Read/Write
When the tape unit
is
ready and in forward status, this
switch sets or resets the tape unit read/write status
trigger.
Count 5
This switch provides two ranges for the variable go-up and
go-down controls. When in the off position, go-up and
go-down time may be independently varied from approxi-
mately 2 ms to 30 ms. When this switch is set to CT5,
go-up and go-down may be varied from approximately
300 ms to 6 seconds, permitting the start/stop envelope
to be checked for count 5 conditions.
16
Start/Stop
The starting and stopping of tape is controlled by this
three-position switch. In the start position, tape moves
intermittently under control of a multivibrator, the count
5 setting, and go-up and go-down controls. In the go
position, tape moves continuously. In the stop position,
go is inactive, tape does not move, and the rewind/unload
switch is enabled.
Forward/Backward
This switch controls the direction of tape motion in the
tape unit. The backward position disables the set read and
set write lines to the tape unit.
Mode
This two-position rotary switch selects the proper cir-
cuitry for either PE or NRZI recording, as required by
the model of tape unit being tested.
Write Frequency/Model
This rotary switch selects the proper recording mode and
write frequency for the model of tape unit being tested.
Set to model 6 for 2420-7 operation.
Go-Up and Go-Down
These controls proVide for varying the go-up and go-down
time. Two ranges are prOVided, depending on the setting
of the count 5 switch. With the count 5 switch off, go-up
and/or go-down may be varied from 2 ms to 30 ms
(approXimately). With the count 5 switch set to CT5,
go-up and/or go-down is varied from 300 ms to 6 seconds
(approxima tely).
Read Scan 1
This rotary switch connects anyone of the nine read
buses to the read scan 1 signal hub. If the mode switch is
set to NRZI, this same read signal is amplified and
available for checking at the asymmetry jack.
Read Scan 2
This rotary switch connects anyone of the nine read
buses to the read scan 2 signal hub.
Bit Switches
Each bit switch set to 1 during a write operation causes
I-bits to be written continuously in the corresponding
track. Switches set to 0 cause the corresponding tracks to
be erased.
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