49
(2) Remove the battery pack.
(3) Remove the sensor grill cover by removing the
three screws on the front of the instrument to
access the sensor compartment.
(4) Gently pull all of the sensors out of their
sockets.
(5) Remove the 6 screws holding the instrument
case together as shown in
Figure 5.3.1
and
separate the two halves of the case. (Be careful
to note which screws are equipped with O-rings,
and which are used to secure the weather cover
snaps.)
(6) Carefully remove the main circuit board and
liquid crystal display assembly from the
instrument housing.
(7) Disconnect the three-wire plug that connects the
main board to the audible alarm.
(8) Turn the main circuit board over to locate the
PROM chip in its socket. Note the exact
orientation of the chip in the socket.
Note: The PROM chip is located on the
same side of the main circuit board as the
four light emitting diodes (LEDs) and LCD
ribbon connector. The PROM is located in a
socket near the upper right hand corner of
the board as shown in Figure 5.3.2. The
reference designator (an electronic
component indicator number printed on the
main circuit board) is “U23”.
(9) Use the chip extraction tool supplied with the
replacement PROM to remove the old PROM
chip. (It is usually best to gently rock the tool
back and forth to loosen the PROM from the
socket rather than pulling it straight out.)
Note: Biosystems strongly recommends use of
a PROM removal tool or "chip puller" to remove
the old PROM. A chip puller should have been
supplied with your replacement PROM. Do not
use small screwdrivers or other non-
recommended devices to remove the old PROM!
Use of non-recommended devices can easily
cause damage to the PROM socket.
Chip pullers are readily available from most
local electronic supply stores or may be
obtained directly from Biosystems.
(10)
Insert the new PROM chip into the socket.
Be careful to properly align the flat corner of the
chip with the flat corner of the PROM socket.
(11)
Reinstall the main board. Make sure the
ribbon cable connecting the main board to the
meter display board and the audible alarm
connector are properly attached.
Be careful not to crimp any wires as the main
board is reattached.
(12)
Reassemble the case, being careful the
protective gasket is properly positioned between
the two sections of the instrument case. Make
sure that all screws, snaps, and O-rings are
properly positioned.
(13)
Replace the battery pack.
(14)
Re-initialize the PhD Ultra as discussed in
Section 4.4 of this manual.
(15)
Verify that all configuration, alarm and
service due settings are correct.
(14)
Calibrate the instrument before returning
to service!
Figure 5.3.1. PhD Ultra upper and lower case
assembly
5.3.2. PhD Ultra main circuit board (showing
placement of software PROM)
5.4
Motorized pump maintenance
Use of the optional motorized sample draw pump
(part number 54-05-A0101) allows the PhD Ultra to
continuously monitor remote locations. The slip-on
pump obtains power directly from the PhD Ultra
battery, and runs continuously as long as the
instrument is turned on. The instrument constantly
monitors the pump for proper performance. (A
flashing “P” indicator is the upper left corner of the
