Teledyne 9110T - Nitrogen Oxides Analyzer - Manual (Page 314)

Model 9110T NOx Analyzer Troubleshooting & Service
Teledyne Analytical Instruments 314
13. Change the PMT or the HVPS or both, clean the PMT glass tube with a clean, anti-
static wipe and do not touch it after cleaning.
14. If the cold block or TEC is to be changed:
 Disconnect the TEC driver board from the preamplifier board, remove the cooler
fan duct (4 screws on its side) including the driver board.
 Disconnect the driver board from the TEC and set the sub-assembly aside.
15. Remove the end plate with the cooling fins (4 screws) and slide out the PMT cold
block assembly, which contains the TEC.
16. Unscrew the TEC from the cooling fins and the cold block and replace it with a new
unit.
17. Reassemble this TEC subassembly in reverse order.
 Ensure to use thermal grease between TEC and cooling fins as well as between
TEC and cold block and that the side opening in the cold block will face the
reaction cell when assembled.
 Evenly tighten the long mounting screws for good thermal conductivity.
C
AUTION
Q UALIFIED P ERSONNEL
The thermo-electric cooler needs to be mounted flat to the heat sink.
If there is any significant gap, the TEC might burn out. Ensure to apply heat sink
paste before mounting it and tighten the screws evenly and cross-wise.
18. Reinsert the TEC subassembly in reverse order.
 Ensure that the O-ring is placed properly and the assembly is tightened evenly.
19. Insert the LED and thermistor into the cold block, insert new drying packages and
carefully replace the end plate by making sure that the O-ring is properly in place.
 Improperly placed O-rings will cause leaks, which – in turn – cause moisture to
condense on the inside of the cooler and likely cause a short in the HVPS.
20. Reinsert the PMT/HVPS subassembly in reverse order.
 Don’t forget the gasket between HVPS and PMT.
 Use new plastic screws to mount the PMT assembly on the PMT cold block.
21. Install new silica gel packets (desiccant bags).
22. Reconnect the cables and the reaction cell (evenly tighten these screws).
23. Replace the sensor assembly into the chassis and fasten with four screws and
washers.
24. Reconnect all electrical and pneumatic connections.