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5.5.2
various clip-on connections for tiny 100-pin IC legs.
Digital dc voltmeter.
Extension cable, allowing the drive to be operated on a
bench while connected to power.
Connection to the SCSI bus
is not required.
Techniques and Waveform Descriptions
Place the drive so the PCB is easily accessible.
Remove the WS
shorting plug, if installed.
Plug in power, but not the SCSI bus
connector.
The waveforms are shown in Figures 2-12, 5-1, 5-2 and 5-3
and the schematics are in SECTION 3.
CAUTION
Be careful not to short IC pins together or to
ground.
Be especially careful with -WR GATE
and -BUF WR GATE.
If either of these signals is
shorted to ground or another signal, the drive may
write over and destroy data and servo tracks.
Some of the signals can be observed at J5, the
test connector, where there is less danger of
shorts.
1.
DC Voltages
Measure (all + with respect to ground):
5 V dc and 12 V dc input power, near J2, or on J5.
3.7 V dc reference voltage at pin 10 of U28.
2.5 V dc reference voltage at pin 11 of U10.
3.7 V dc reference voltage at pin 12 of U10.
2.
Spin-up
Listen to the motor spin up.
In order for the motor to spin, there
must be:
o
A continuous low level on U8, pin 2.
DICEY asserts this
-SPIN signal after the RAM test and other initialization
tests are passed.
o
1 V peak-to-peak at 2 MHz on top of 1 V dc, on U8, pin 4.
The 2 MHz is derived from the 12 MHz clock, divided down by
FYLO, U9.
5-3
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