Teledyne T200H User Manual page 262

Troubleshooting & Service
Note
260
6. Remove the dryer packages inside the PMT housing.
7. Along with the plate, slide out the OPTIC TEST (O-Test) LED and the thermistor
that measures the PMT temperature (shown in Figure 7-18).
8. Unscrew the PMT assembly, which is held to the cold block by two plastic screws.
9. 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).
a) Carefully remove the assembly consisting of the HVPS, the gasket and the PMT.
Both may be coated with a white, thermal conducting paste.
b) Do not contaminate the inside of the housing with this grease, as it may
contaminate the PMT glass tube on re-assembly.
10. 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.
11. If the cold block or TEC is to be changed:
a) Disconnect the TEC driver board from the preamplifier board, remove the cooler
fan duct (4 screws on its side) including the driver board.
b) Disconnect the driver board from the TEC and set the sub-assembly aside.
12. Remove the end plate with the cooling fins (4 screws) and slide out the PMT cold
block assembly, which contains the TEC.
13. Unscrew the TEC from the cooling fins and the cold block and replace it with a new
unit.
14. 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 faces the reaction
cell when assembled.
15. Evenly tighten the long mounting screws for good thermal conductivity.
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 the thermal
pads before mounting it and tighten the screws evenly and cross-wise..
16. Re-insert the TEC subassembly in reverse order.
Make sure that the O-ring is placed properly and the assembly is tightened evenly.
17. Re-insert the PMT/HVPS subassembly in reverse order and don't forget the gasket
between HVPS and PMT.
a) Use new plastic screws to mount the PMT assembly on the PMT cold block.
b) 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.
18. Reconnect the cables and the reaction cell (evenly tighten these screws).
19. Replace the sensor assembly into the chassis and fasten with four screws and
washers.
20. Reconnect all electrical and pneumatic connections.
21. Leak check the system (Section 7.5.1, 7.5.2).
Teledyne API - Model T200H/T200M Operation Manual
07270D DCN7141