Teledyne 9110TH - Nitrogen Oxides Analyzer - Manual (Page 269)

Troubleshooting & Repair Model 9110TH NOx Analyzer
Teledyne Analytical Instruments 249
7.6.5. REPLACING THE PMT, HVPS OR TEC
The photo multiplier tube (PMT) should last for the lifetime of the analyzer. However,
in some cases, the high voltage power supply (HVPS) or the thermo-electric cooler
(TEC) may fail. In case of PMT, HVPS or TEC failure, the sensor assembly needs to be
opened in order to change one of these components. Refer to Figure 7-18 for the
structure of the 9110TH/M sensor assembly and follow the steps below for replacement
of one of its components. We recommend to ensure that the PMT, HVPS or TEC
modules are, indeed, faulty to prevent unnecessary opening of the sensor.
CAUTION
Although it is possible for a skilled technician to change the PMT or HVPS
through the front panel with the sensor assembly mounted to the analyzer,
we recommend to remove the entire assembly and carry this procedure out
on a clean, anti-static table with the user wearing an anti-static wrist strap to
prevent static discharge damage to the assembly or its circuits.
1. Power down the analyzer, disconnect the power cord.
2. Remove the cover and disconnect all pneumatic and electrical connections from the
sensor assembly.
3. If the TEC is to be replaced, remove the reaction cell assembly at this point by
unscrewing two holding screws. This is necessary only if the PMT cold block is to
be removed.
This step is not necessary if the HVPS or the PMT only are exchanged.