data lines.
In this instance probe these lines with an
oscilloscope and look for any address or data lines that are in-
active (no data or periodic state transition).
If an in-active
i,
line is found the processor may be at fault but the problem is
most likely a bad port or latch somewhere on the
bus.
This type
of hardware failure generally requires replacement of the
Audiometer Board,as this is probably the most cost effective way
to resolve this type of problem.
A lock-up may also occur as the result of a defective EPROM
(U505).
This EPROM contains all the instructions for the
processor to execute.
If there are no instructions the processor
may pause or get "LOST".
This type of failure very seldom occurs
as these EPROMS are very stable devices.
When a new processor is
installed into the audiometer board it
may lock-up.
There are internal system configuration registers
that must be loaded by shorting
JP1
pins 1 and 2 (Mode B pin 2 of
the processor to ground) prior to power-up.
After power-up wait
for a period of (2 or 3 seconds) then power the unit down and
remove the jumper.
The operator/technician should then load
default data and perform self calibration (refer to Section 4,
Calibration).
It is important to note that this problem could
also occur if a data error was present in the EEPROM portion of
the processor.
6.7 POWER SUPPLY RELATED PROBLEMS
The GSI 17 is powered by battery or by the Power Module (Battery
Eliminator/AC Adapter).
When a power supply is suspected to be
defective,
first check the power source.
Have the batteries been
replaced? Were the batteries new?
Dated?
Is the power
eliminator functioning properly?
Is there 13 V present at the
connector which attaches to the GSI
17?
When these questions
have been answered then proceed with troubleshooting on the
Audiometer Board.
Check for the presence of 7 Vdc to 13 Vdc at
the positive terminal of
C101
(use
TP100
for ground reference).
Check the positive
terminal of
C100
for
+5
Vdc.
Check the
negative terminal of Cl03 for -5 Vdc.
NOTE:
If any power supply voltage is incorrect the problem may
be the result of a short or load somewhere on the line.
It
is best to try lifting the regulator output pin
and
measure
the
lifted pin prior to replacing the device.
If the
regulator
output is
correct with the pin lifted, check
the power
supply
capacitors for low impedance or a shorted device.
If the operating life of the batteries appears diminished,the low
battery indicator may be improperly calibrated or the GSI 17 is
drawing excessive current. Refer to
Section 4,
Calibration, for
the battery calibration procedure.
53
To Next Page
Loading...
