Teledyne 9110EH - Nitrogen Oxides Analyzer - Manual (Page 240)

Troubleshooting & Repair Model 9110EH Instruction Manual
coated with a white, thermal conducting paste. Do not contaminate the inside of the
housing with this grease, as it may contaminate the PMT glass tube on re-assembly.
• Unscrew the PMT assembly, which is held to the cold block by two plastic screws.
Discard the plastic screws and replace with new screws at the end of this procedure
(the threads get stripped easily and it is recommended to use new screws).
• Carefully take out the assembly consisting of the HVPS, the gasket and the PMT.
• 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.
• 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.
• Remove the end plate with the cooling fins (4 screws) and slide out the PMT cold
block assembly, which contains the TEC.
• Unscrew the TEC from the cooling fins and the cold block and replace it with a new
unit.
• Re-assemble this TEC subassembly in reverse order. Make sure 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.
CAUTION
The thermo-electric cooler needs to be mounted flat to the heat sink. If there is
any significant gap, the TEC might burn out. Make sure to apply heat sink paste
before mounting it and tighten the screws evenly and cross-wise.
• Re-insert the TEC subassembly in reverse order. Make sure that the O-ring is placed
properly and the assembly is tightened evenly.
• Re-insert the PMT/HVPS subassembly in reverse order and don’t forget the gasket
between HVPS and PMT. Use new plastic screws to mount the PMT assembly on the
PMT cold block.
• 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.
• Reconnect the cables and the reaction cell (evenly tighten these screws), replace the
sensor assembly into the chassis and fasten with four screws and washers.
• Reconnect all electrical and pneumatic connections, leak check the system and
power up the analyzer.
• Verify the basic operation of the analyzer using the ETEST and OTEST features or
zero and span gases, then carry out a hardware calibration of the analyzer
(Section 11.6.5) followed by a software calibration.
11.7. Technical Assistance
If this manual and its trouble-shooting / repair sections do not solve your problems,
technical assistance may be obtained from Teledyne-API, Customer Service,
City of Industry
, CA 91748-1020. Phone: +1.626.934.1673 or Fax: 1.626.961.2538
226 M9110EH Rev 0