Part III

Model 6600

 

 

 

 

 

 

 

 

 

The reference and measuring signal at the first stage of integration can be observed by placing the scope probe across capacitors C4 and C5 respectively located at PC Board 1 in the detector unit. A dual trace scope is advantageous but not required for this observation.

The test points’ significance is that they reveal proper switch action. The display shows a sawtooth pattern which is a charge-discharge of the first capacitor in the integrating network. This ripple is the AC component of the reference and measuring signal after the pulses are converted to DC. The sawtooth patterns must be displayed 180 with respect to each other as viewed with a dual trace scope. They must be both present.

If one is missing, this means that the switch is not switching.

If the sawtooth shows a broken pattern, this means the switching action is feeble or irregular.

The faulty condition of the switch can usually be corrected by moving the switch up and down or rotating it in its holder.

The magnetic mercury reed switch is activated by the action of a bar magnet and a rotating chopper disc.

An aluminum motor mounting block houses a bar magnet. This bar magnet is positioned in parallel with the mercury chopper switch.

The chopper disc is the green and black disc mounted on the filter wheel shaft next to the motor. The disc is composed of both magnetic and nonmagnetic materials.

As the shaft rotates, the magnetic portion of the disc shorts the magnetic flux as it passes between the magnet and the switch. The nonmagnetic portion of the disc will allow flux lines from the bar magnet to activate the mercury switch.

7.6Sample Cell Maintenance

The Sample Cell needs inspection every 6 weeks. For E.P. systems, open the sample compartment and inspect the cell windows for dirt and oil film. This inspection can be quickly done by removing the external folded optyical path assembly from the main Control/Analysis Unit. Disassemble all, clean and reassemble exactly as before. Re-zero and span calibrate the unit preferably with zero prepared water and span fluids. Thereafter, recheck span flow as appli- cable. Reset span flag valu to new calibration values as performed during startup procedure.

CAUTION: wear UV goggles if lamp left on.

1-42 Part III Teledyne Analytical Instruments

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Teledyne 6600 manual Sample Cell Maintenance