Specifications

AINTENANCE AND

ROUBLESHOOTING

748410-A

August 1999

Chemiluminescense Detector Analyzer Module

Rosemount Analytical NGA 2000

Reaction Chamber Installation

To reinstall, hold the housing in the inverted position while sliding the Reaction Chamber

O-ring and window into position and the tubing into the slot in the housing. Hold the

Reaction Chamber in place while rotating the housing upright. Replace the hold-down

screws.

The procedure described above is for the purpose of maintaining the relative

positions of windows and O-ring to the Reaction Chamber during installation.

Replace the top cap and screws. Reverse the removal procedure to reinstall the Detector

Assembly into the Analyzer Module.

Photodiode Removal

Remove the Detector Assembly as described above. Invert the housing to access the

mounting bracket. Remove the (3) screws and shoulder washers from the bracket. Remove

the bracket, insulating disk and bottom plate as a unit to minimize the spread of the heatsink

compound.

Remove the (2) screws holding the lower section of the Detector Housing, then slide the

section along the cable and remove.

Remove the (2) screws holding the socket, thermistor and photodiode in place, being

careful not to lose the washers that are used as shims.

Grasp the socket and photodiode base while slowly rotating to separate the photodiode

from the housing. Some friction will be felt as an O-ring is used around the photodiode as a

seal.

Photodiode Installation

To replace the photodiode, carefully remove the diode from the green socket, and replace

with a new one. Before mounting the new diode, the top cap of the enclosure should be

temporarily removed and the (2) screws holding the Reaction Chamber loosened about two

turns. This allows air which is trapped between the O-ring seals to escape when the diode is

inserted. It also maintains the position of the O-ring and window in the upper compartment.

The new photodiode should be slowly inserted into the housing while gradually rotating the

body. This allows the O-ring to properly seat. Continue replacing screws, washers,

thermistors, etc., with the thicker shim (washer) on the opposite side of the socket from the

thermistor.

NOTE