Carbon Monoxide Alarm User Manual

Page 35
the value for the sensor in question should be within the
range listed in Section 5.2.2.1. If the sensor checks out,
recalibrate. Replace sensor if necessary.
7.2.3.5 Problem: "X" appears under channel
display for combustible gas
Possible causes:
Sensor failure. Loose connection.
Solution(s):
Tighten connections. Check sensor. Check output in
Diagnostics Test mode. Replace sensor if necessary.
7.2.3.6. Problem: Unstable oxygen readings
Possible causes:
Sensor failure. Loose connection.
Solution(s):
Check in Diagnostics Test mode, 595-935 counts
acceptable. If sensor checks out, examine retaining nuts
for tightness. Replace O2 sensor if necessary.
7.2.3.7 Problem: Display is blank
Possible causes:
Battery voltage too low. Operating temperature too low.
Bad LCD display assembly. Microprocessor locked-up or
"crashed."
Solution(s):
Take the instrument to a non-hazardous location. If cold,
allow instrument to warm back up to room temperature.
Plug the PhD
2
into the battery charger for several
minutes. With the instrument still connected to the
battery charger, attempt to turn the detector on. If this
works, the battery needs to be recharged or replaced. If
the instrument still fails to turn on, re-boot the
microprocessor using the procedures discussed in
Section 7.2.1. If the instrument still fails to turn on,
return to factory for repair.
7.2.3.8 Problem: No audible alarm
Possible causes:
Loose connection, alarm failure.
Solution(s):
Return to factory for repair.
7.2.3.9 Problem: Function keypad (+,-, Cal,
Alarm) doesn't work
Possible causes:
Not in Technician mode, microprocessor locked-up or
"crashed," loose connection, switch failure.
Solution(s)
Switch to Technician operating mode. Take the
instrument to a non-hazardous location. Plug the PhD
2
into the battery charger for several minutes. With the
instrument still connected to the battery charger, attempt
to turn the detector on. If this works, the battery needs to
be recharged or replaced. If the instrument still fails to
turn on, re-boot the microprocessor using the procedures
discussed in Section 7.2.1. If keypad buttons still fail to
function, return to factory for repair.
7.3 Changing the PhD
2
microprocessor PROM chip
The PhD
2
is a microprocessor controlled design. A
Programmable Read Only Memory (PROM) chip located
on the main circuit board is used to program the
instrument. New microprocessor software versions are
installed by removing the old PROM chip, and replacing it
with the newer version.
Note: PROM chip replacement requires opening the
instrument and removing an electronic component
located on the main circuit board of the detector.
This procedure should not be done by unauthorized
persons. In many cases it may be better to return the
detector to the factory for this procedure.
To replace the PhD
2
PROM chip:
(1) Make sure that the PhD
2
is turned off.
(2) Remove the five screws holding the instrument case
together and separate the two halves of the case.
(3) If the PhD
2
is equipped with an internally housed
lead acid battery, carefully pull the battery free of the
case.
Be careful not to disconnect the battery from the
main board! Disconnection of the battery will result
in the loss of recorded data.
If the PhD
2
is equipped with an externally removable
NiCad battery, simply leave the battery installed in its
normal position on the bottom of the lower half of the
instrument case.
(4) Remove the four Phillips head screws securing the
main circuit board to the instrument case.
(5) Disconnect the ribbon cable which connects the main
board to the meter display board.
(6) Carefully remove the PROM chip (IC-10) from its
socket.
(See Figure 7.3. for location of IC-10.)
Note: Biosystems strongly recommends use of a
PROM removal tool or "chip puller" to remove the IC.
Chip pullers are readily available at your nearest
electronics supply store.
(7) Insert the new PROM chip into the socket, being
careful to properly align position marks.