Disk Controller Board Checkout - NorthStar HORIZON Manual

DISK CONTROLLER BOARD CHECKOUT
The following checkout procedure may be followed for a newly
assembled board. However, you may choose to skip this section
and return to it later only if the disk controller does not seem
to be operating correctly. It can also be used to diagnose
problems in previously operational boards.
The following terms are used in specifying eXDected test results:
GND
LOVi
HIGH
+5V
AC
ground, 0 volts DC
logic zero, 0-.7 volts, normally about .3 volts
logic one, 2.4-5.0 volts, normally about 3 volts
+5 volts from power supplv
Signal with pulses (as opposed to DC signal)
Vihen referring to the name of a signal from the schematic
drawings, if the signal is identified with a bar over its name,
then the name is followed by a slash (e.g., STORE/) in the
checkout instructions. When describing an AC pulse, the notation
(±W,P) refers to a positive or negative pulse with a width of W
appearing with a period of P. For example, a Dositive pulse with
width 120 nanoseconds appearing every 25 microseconds would be
described as (+120ns,25us) See Appendix 1 for details on how to
detect pulse signals.
If an oscilloscope will be used to test the board, a "scope
ground" may be installed by soldering a "bridge" of jumper wire
between the two PC board holes that connect edge connector pins
50 and 100 near location l2D. Note that either of the two
regulator machine screws can also be used for ground test points.
Gl. with the computer power off, install only the disk
controller board into the motherboard. The ribbon cable
should not be plugged into the board. Turn on the computer
power and check for the following counter timing signals:
SIGNAL
LCLK/
CC3
CC6
Cell
Cel5
SC03
(no name)
AUTO-Off'
LOCATION
l5B pin 12
6A pin 11
7A pin 11
8A pin 11
9A pin 11
l5C pin 6
3D pin 6
6C pin 11
DESCRIPTION
AC, 500ns square wave
AC, Sus square wave
AC, l28us square wave (some jitte
AC, 2ms square wave (some jitter)
AC, 32ms square wave (some jitter
AC, 500ms square wave
AC, 8.3sec square wave
AC, (+8.3sec,33sec)
If the signals are not as listed then refer to the schematic
drawings and trace backwards to locate and correct the
problem.
North Star HORIZON Computer
50