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SECTION V
Replacement of electronic circuit boards:
The HPT 100 should provide reliable operation over an extended period of time. If you
suspect the unit is inoperative, please refer to Section IV for information on using the
Diagnostic Shunt to determine if your unit is working properly. Please replace the circuit
board only if you determine that the board may be defective. Use of a conductive work
table and wrist strap is required as the boards are static sensitive. Consult factory for
proper training prior to performing field service. As any safety approvals are voided by
modifications or non factory repairs to the HPT 100, return safety listed products to
Ametek for service. Ametek is not responsible for improperly serviced units.
1.
Remove all power from the unit.
2.
Open the threaded cover ring or conduit adapter near the top of the unit by turning in a
counter clockwise direction.
3.
Remove the Mil connector/filter assembly or pigtail/filter assembly by pulling out with your
hand. Make a note of the original orientation of the filters as they must be replaced in the
same location.
4.
In most cases, the filter assembly will come out leaving the main board in place. If so, use a
needle nose pliers and gently pull out the main board by pulling on the raised center tab at
the top of the center of the board.
5.
Note the location of the compensator board assembly. This component is a 14 pin DIP
package connected to the main board with 14 gold pins. Before removing the compensator
board, note the orientation of the part to assist in remounting to a new main circuit board
assembly. Remove the compensator network using a DIP extractor to prevent bending pins.
6.
Re mount the compensator board noting the orientation into a spare circuit board assembly,
(K574514 for 4/20 mA version or K574518 for 0-5 Vdc). Push compensator board all the
way in, to provide clearance for the case to slide over it.
7.
Observe the round case from the top and note the location of a welded key opposite to the pot
access cover (this is employed in earlier style units). Note the flat on the round circuit board
of the main circuit board assembly. Remount the assembly by placing the flat next to the key
(when utilized) or in the original orientation (when not utilized) and insert the board
assembly until the board snaps into the mating connector. This can be done with your finger.
8.
Insert the Mil connector/filter assembly or pigtail/filter assembly by first noting the location
of the indent adjacent to one threaded filter and on the underside of the assembly(when
utilized) or by reference to original orientation. Note also the two holes in the round circuit
board (three for voltage output units) which is part of the main circuit board assembly. For
earlier style units, line the indent to the key welded to the case and carefully insert the Mil
connector/filter assembly or pigtail/filter into the round board. For later style units rely on
the orientation notes made during disassembly. Make sure the filter leads line up with the
available mating holes on the round circuit board. Gently push in but do not force or you
will bend the filter leads. Gently continue until mating is achieved.
9.
Place the threaded cover ring or conduit adapter back on the top of the unit and turn
clockwise to seal (do not apply excessive force or damage will result). Recalibrate the unit
using the procedure outlined in Section IV. (field service calibration)
pg. 5-2
SERVICE
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