Model 755R

Instruction Manual

748213-S April 2002

pins 15 and 16 of the detector connector J12, should be approximately 89 ohms.

If resistance is correct, and the combined resistance is incorrect, heater HR1 may be open.

To reach the leads of HR1, remove the circuit board on the heater assembly. Resistance of HR1 should be approximately 21 ohms.

To check operation of the heater circuit, connect a voltmeter across R61 on the Power Supply Board. Normally, the voltage will be 4

VDC when cold and will drop to approximately

0.4VDC at control temperature. Temperature sensor RT1 is mounted in the detector, with leads accessible at pins 10 and 11 of detector connector J12. The sensor resistance should be 1M ohms at 25°C and approximately 149K ohms at operating temperature of 65°C.

A. Detector/Magnet Assembly - Exploded View

B. Optical Bench - Exploded View

 

 

Connector

Sample Pre-Heating

 

J12

Coil

 

 

Connector

Photocell

 

Lock Screws (2)

 

Board

 

 

 

Sample Inlet

 

 

Tube

 

 

Sample Out-

 

Dual

let Tube

 

Lamp Retaining

Photocell

 

 

 

 

Set Screw

 

Magnet

 

 

Detector Assembly Assembly

Lamp Viewing

 

Optical Bench Assembly

Source Lamp

Hole

Assembly

Mounting Screws (2)

 

 

 

Figure 6-1. Detector/Magnet Assembly

Rosemount Analytical Inc. A Division of Emerson Process Management

Maintenance and Service

6-3